2015 overview
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2015 Outfall monitoring o verview 1 Massachusetts Water Resources Authority Environmental Quality Department Report 2016-11 Citation : Werme C, Keay KE, Libby, PS, Wu DC, Taylor DI, Codiga DL. 2016. 2015 outfall monitoring overview . Boston: Massachusetts Water Resources Authority. Report 2016-11. 64 p. 2015 Outfall Monitoring Overview prepared by Christine Werme Independent Consultant Oakland, CA 94612 Kenneth E. Keay Massachusetts Water Resources Authority Environmental Quality Department 100 First Avenue Charlestown Navy Yard Boston, MA 02129 P. Scott Libby Battelle 157 Park Row Brunswick, ME 04011 David C. Wu, David I. Taylor, Daniel L. Codiga Massachusetts Water Resources Authority Environmental Quality Department 100 First Avenue Charlestown Navy Yard Boston, MA 02129 November 4, 2016 2015 Outfall Monitoring Panel and Committees Outfall Monitoring Science Advisory Panel (OMSAP) Robert Beardsley, Woods Hole Oceanographic Institution Robert Kenney, University of Rhode Island Judy Pederson, Massachusetts Institute of Technology Sea Grant Michael Shiaris, University of Massachusetts, Boston James Shine, Harvard School of Public Health Geoffrey Trussell, Northeastern University Marine Science Center Juanita Urban-Rich, University of Massachusetts, Boston Inter-Agency Advisory Committee (IAAC) US Geological Survey Massachusetts Coastal Zone Management US Army Corps of Engineers Stellwagen Bank National Marine Sanctuary US Environmental Protection Agency Massachusetts Division of Marine Fisheries Massachusetts Department of Environmental Protection Public Interest Advisory Committee (PIAC) Save the Harbor/Save the Bay MWRA Wastewater Advisory Committee Conservation Law Foundation Massachusetts Audubon Society MWRA Advisory Board Association to Preserve Cape Cod Safer Waters in Massachusetts The Boston Harbor Association i Table of Contents Summary ....................................................................................................................... v 1. Introduction ............................................................................................................... 1 2. Effluent ..................................................................................................................... 2 2015 Characterization ............................................................................................... 2 Contingency Plan Thresholds ................................................................................... 7 3. Water Column ........................................................................................................... 8 Physical Conditions .................................................................................................. 9 Water Quality .......................................................................................................... 12 Phytoplankton Communities ................................................................................... 19 Zooplankton Communities...................................................................................... 22 Stellwagen Bank National Marine Sanctuary ......................................................... 24 Boston Harbor ......................................................................................................... 26 Contingency Plan Thresholds ................................................................................. 28 4. Sea Floor ................................................................................................................. 30 Sediment Characteristics and Tracers ..................................................................... 32 Soft-bottom Communities ....................................................................................... 34 Sediment-profile Imaging ....................................................................................... 35 Stellwagen Bank National Marine Sanctuary ......................................................... 39 Boston Harbor ......................................................................................................... 40 Contingency Plan Thresholds ................................................................................. 42 5. Fish and Shellfish .................................................................................................... 44 Flounder Health ...................................................................................................... 45 Fish and Shellfish Chemistry .................................................................................. 47 Contingency Plan Thresholds ................................................................................. 51 6. Special Studies ........................................................................................................ 52 Eelgrass in Boston Harbor ...................................................................................... 52 Bacterial Water Quality in Boston Harbor and Massachusetts Bay ....................... 54 Winter Flounder Sex Ratios .................................................................................... 58 Cape Cod Bay Studies ............................................................................................ 60 References ................................................................................................................... 63 List of Acronyms ........................................................................................................ 64 ii List of Figures Figure 2-1. Annual rainfall in Boston, 1990–2015 ....................................................... 2 Figure 2-2. Annual primary-blended and full secondary effluent flows, 1999–2015 .. 3 Figure 2-3. Monthly primary-blended and full secondary effluent flows during 2015. 3 Figure 2-4. Annual solids discharges, 1990–2015 ........................................................ 4 Figure 2-5. Annual nitrogen discharges, 1999–2015 .................................................... 5 Figure 2-6. Annual metals discharges, 1999–2015 ....................................................... 6 Figure 2-7. Annual PAH discharges, 2006–2015 ......................................................... 6 Figure 3-1. Water-column monitoring stations ............................................................. 8 Figure 3-2. Flows of the Merrimack and Charles rivers ............................................. 10 Figure 3-3. Nearfield surface water temperature at the NDCB Buoy 44013.............. 11 Figure 3-4. Average north-south component of wind stress at NDBC Buoy 44013. . 11 Figure 3-5. Depth-averaged dissolved inorganic nutrient concentrations at Station N18 in 2015 compared to prior years ......................................................................... 12 Figure 3-6. Depth-averaged ammonium concentrations by station in Massachusetts and Cape Cod bays in 2015 ........................................................................................ 13 Figure 3-7. (Left) Surface- and bottom-water ammonium on April 13, 2015 at the monitoring stations during mixed conditions. (Right) Cross-sections of concentrations throughout the water column along transects connecting selected stations ................ 14 Figure 3-8. (Left) Surface- and bottom-water ammonium on August 18, 2015 at the monitoring stations during stratified conditions. (Right) Cross-sections of concentrations throughout the water column along transects connecting selected stations ........................................................................................................................ 15 Figure 3-9. Average areal chlorophyll by station in Massachusetts Bay in 2015....... 16 Figure 3-10. Satellite imagery of surface chlorophyll concentrations in 2015. .......... 17 Figure 3-11. Surface- and bottom-water dissolved oxygen concentrations at nearfield Station N18 in 2015 compared to prior years ............................................................. 18 Figure 3-12. Total phytoplankton abundance at selected stations in 2015 compared to prior years ................................................................................................................... 19 Figure 3-13. Mean nearfield abundance of Phaeocystis pouchetii , 1992–2015. ........ 20 Figure 3-14. Nearfield abundance of Alexandrium fundyense , 1992–2015................ 21 Figure 3-15. Long-term trend in nearfield total zooplankton and copepods, derived from a time-series analysis, compared to the multiyear means. ................................. 22 Figure 3-16. Total zooplankton abundance at selected stations in 2015 compared to prior yearsr. ................................................................................................................. 23 Figure 3-17. Long-term trend in annual total phytoplankton and total zooplankton in the nearfield. ............................................................................................................... 24 Figure 3-18. Chlorophyll measurements at NERACOOS Buoy A01, inside Stellwagen Bank Marine Sanctuary, and at nearby Station F22 ................................. 25 Figure 3-19. Bottom water dissolved oxygen concentrations at NERACOOS Buoy A01, inside Stellwagen Bank Marine Sanctuary, and at nearby Station F22 ............. 25 iii Figure 3-20. (Top) Depth-averaged ammonium levels at Station F23 in Boston Harbor. (Bottom) Depth-averaged ammonium levels at Station N18 near the Massachusetts Bay outfall........................................................................................... 27 Figure 3-21. Acartia spp. abundance at Station F23 in Boston Harbor in 2015 compared to prior years. ............................................................................................. 28 Figure 4-1. Soft-bottom monitoring stations. ............................................................. 30 Figure 4-2. Sediment-profile imaging stations ........................................................... 31 Figure 4-3. Concentrations of Clostridium perfringens spores, corrected for sediment grain size, in 2015 ....................................................................................................... 33 Figure 4-4. Mean concentrations of Clostridium perfringens spores during the baseline and outfall discharge years ........................................................................... 33 Figure 4-5. Mean infaunal abundance per sample in four areas of Massachusetts Bay, 1992–2015................................................................................................................... 34 Figure 4-6. Percent fine sediments superimposed on the ordination plot of the 2015 infauna samples. .......................................................................................................... 35 Figure 4-7. Apparent change in sediment grain-size distribution between 2014 and 2015 at Stations NF02 and NF17. ............................................................................... 36 Figure 4-8. Annual apparent color RPD depth for data from nearfield stations. ........ 37 Figure 4-9. Numbers of studies showing types of adverse effects on benthic communities observed in studies of effluent outfalls on coastal and ocean communities. ............................................................................................................... 38 Figure 4-10. Depth superimposed on the ordination plot of the 2015 infauna samples. ..................................................................................................................................... 39 Figure 4-11. Soft-bottom sampling stations in Boston Harbor. Nine stations are sampled each year for sediment characteristics and infauna analyses ........................ 40 Figure 4-12. Mean concentrations of Clostridium perfringens spores at selected harbor stations, 1991–2015 ......................................................................................... 41 Figure 4-13. Ordination plot of 2015 Boston Harbor infauna samples. ..................... 41 Figure 4-14. Annual community parameters with nearfield Contingency Plan thresholds .................................................................................................................... 43 Figure 5-1. Fish-and-shellfish monitoring stations ..................................................... 44 Figure 5-2. Annual prevalence of centrotubular hydropic vacuolation, 1991–2015 .. 46 Figure 5-3. Total chlordane in flounder fillets, 1995–2015 ........................................ 48 Figure 5-4. Total chlordane in lobster meat, 1994–2015 ............................................ 48 Figure 5-5. Low molecular weight PAHs in deployed mussels, 1991–2015.............. 49 Figure 5-6. Silver in flounder livers, 1995–2015 ........................................................ 50 Figure 5-7. Lead in deployed mussels, 1991–2015 .................................................... 50 Figure 6-1. Percent eelgrass coverage vs. nitrogen loading in coastal systems compared to Boston Harbor before and after the Boston Harbor Project ................... 53 Figure 6-2. Eelgrass coverage in the north harbor, 1995–2012 .................................. 54 Figure 6-3. Bacterial water quality prior to the Boston Harbor Project and after completion of the treatment plant and most CSO projects. ........................................ 55 Figure 6-4. Stations monitored for sewage-indicator bacteria and the outfall diffuser ..................................................................................................................................... 56 iv Figure 6-5. Enterococcus , 1999–2014, compared to the contact recreation standard ..................................................................................................................................... 57 Figure 6-6. Fecal coliform bacteria, 1999–2014, compared to the shellfishing standard ..................................................................................................................................... 57 Figure 6-7. Proportion of catch made up of female flounder, 1991–2015 ................. 58 Figure 6-8. Percent female flounder taken from the vicinity of the outfall site, 1991– 2015............................................................................................................................. 59 Figure 6-9. Sex ratios compared to total length of winter flounder in MWRA surveys, other northeast coastal surveys, and on offshore Georges Bank ................................ 60 Figure 6-10. The Center for Coastal Studies monitors its own eight stations and three MWRA stations in and near Cape Cod Bay ............................................................... 61 Figure 6-11. Right whale sightings in Cape Cod Bay, 1998–2015 ............................ 62 Figure 6-12. Whale sightings in Cape Cod Bay in May 2015 .................................... 62 List of Tables Table i. Contingency Plan threshold values and 2015 results for effluent monitoring. ...................................................................................................................................... vi Table ii. Contingency Plan threshold values and 2015 results for water-column monitoring. .................................................................................................................. vii Table iii. Contingency Plan threshold values and 2015 results for seafloor monitoring. .................................................................................................................................... viii Table iv. Contingency Plan threshold values and 2015 result for fish-and-shellfish monitoring .................................................................................................................... ix Table 2-1. Contingency Plan threshold values and 2015 results for effluent monitoring. .................................................................................................................... 7 Table 3-1. Contingency Plan threshold values and 2015 results for water-column monitoring. .................................................................................................................. 29 Table 4-1. Contingency Plan threshold values and 2015 results for seafloor monitoring. .................................................................................................................. 42 Table 5-1. Contingency Plan threshold values and 2015 result for fish-and-shellfish monitoring. .................................................................................................................. 51 v Summary Each year, the Massachusetts Water Resources Authority (MWRA) prepares an overview of environmental monitoring related to the discharge of municipal wastewater effluent from Deer Island Treatment Plant through an offshore outfall tunnel into Massachusetts Bay. The report presents monitoring results and information relevant to MWRA’s permit-required Contingency Plan, including threshold exceedances and permit violations, responses, and, if needed, corrective actions. The overview also includes monitoring results relevant to the Stellwagen Bank National Marine Sanctuary and information on special studies conducted in response to specific permit requirements, scientific questions, or public concerns. This report for the 2015 monitoring year marks more than fifteen years since September 2000, when MWRA ceased discharge of wastewater effluent to the relatively confined waters of Boston Harbor and began to discharge into deeper, less confined waters in Massachusetts Bay. Before September 2000, MWRA had completed almost nine years of baseline monitoring. This report for 2015 includes results of effluent analyses; water- column, seafloor, and fish-and-shellfish monitoring in the vicinity of the outfall (the “nearfield”) and at reference stations; and results pertinent to Stellwagen Bank and to Boston Harbor. This year’s report on special studies focuses on eelgrass in Boston Harbor, bacterial water quality in Boston Harbor and Massachusetts Bay, winter flounder sex ratios, and ongoing Cape Cod Bay studies. Operations at the Deer Island Treatment Plant continued to be exceptional in 2015, earning MWRA a National Association of Clean Water Agencies (NACWA) Platinum 9 Peak Performance Award. This NACWA award recognizes facilities with 100% compliance with permit effluent limits for nine consecutive years. Nearfield and reference-station monitoring results from 2015 were consistent both with predictions made during the outfall siting process and with past results, showing no unanticipated effects of the discharge (Tables i through iv). No Contingency Plan “warning-level” exceedances were observed. A “caution-level” exceedance * occurred for one water- column parameter, summer levels of the nuisance algal species Phaeocystis pouchetii . This exceedance was due to presence of Phaeocystis at a low abundance in one sample during the May survey and was likely caused by a weather-related delay of the seasonal phytoplankton cycle. Except for a number of exceedances of the Phaeocystis thresholds, which resulted from wide regional blooms, water-column exceedances have been rare throughout the course of monitoring and have not been indicative of problems at the treatment plant or in the environment. * MWRA’s discharge permit includes Contingency Plan thresholds, indicators that may signal a need for action. The thresholds are based on permit limits, state water quality standards, and expert judgment. “Caution-level” thresholds indicate a need for a closer look at the data to determine the reason for an observed change. “Warning-level” thresholds are a higher level of concern, and the permit requires a series of steps to evaluate whether adverse effects occurred and if so, whether they were related to the discharge. If exceedances were related to the discharge, MWRA might need to implement corrective action. All thresholds based on effluent discharge permit limits are warning-level. Some ambient parameters have both caution- and warning-level thresholds, and others have only caution-level thresholds. vi Table i. Contingency Plan threshold values and 2015 results for effluent monitoring. Parameter Baseline Caution Level Warning Level 2015 Results pH NA None <6 or >9 Not exceeded Fecal coliform NA None > 14,000 fecal coliforms/100 mL Not exceeded Chlorine, residual NA None > 631 μ g/L daily, > 456 μ g/L monthly Not exceeded Suspended solids NA None > 45 mg/L weekly > 30 mg/L monthly Not exceeded cBOD NA None > 40 mg/L weekly, > 25 mg/L monthly Not exceeded Acute toxicity NA None LC50 <50% Not exceeded Chronic toxicity NA None NOEC <1.5% effluent Not exceeded PCBs NA Aroclor > 0.045 ng/L None Not exceeded Plant performance NA > 5 violations/year Compliance <95% of the time Not exceeded Flow NA None >436 MGD average dry days Not exceeded Total nitrogen load NA > 12,500 mtons/year > 14,000 mtons/year Not exceeded Oil and grease NA None > 15 mg/L weekly Not exceeded NA = not applicable cBOD = carbonaceous biological oxygen demand LC50 = 50% mortality concentration NOEC = no observable effect concentration PCB = polychlorinated biphenyl Plant performance = compliance with permit conditions vii Table ii. Contingency Plan threshold values and 2015 results for water-column monitoring. Parameter Baseline Caution Level Warning Level 2015 Results Dissolved oxygen* Nearfield concentration 6.05 mg/L < 6.5 mg/L < 6.0 mg/L 7.56 mg/L Nearfield percent saturation 65.3% < 80% < 75% 84.5 % Stellwagen concentration 6.23 mg/L < 6.5 mg/L < 6.0 mg/L 7.44 mg/L Stellwagen percent saturation 67.2% < 80 < 75% 79.6 % Nearfield depletion rate 0.024 mg/L/d > 0.037 mg/L/d > 0.049 mg/L/d 0.018 mg/L/d Chlorophyll Annual 72 mg/m 2 > 108 mg/m 2 > 144 mg/m 2 87 mg/m 2 Winter/spring 50 mg/m 2 > 199 mg/m 2 None 122 mg/m 2 Summer 51 mg/m 2 > 89 mg/m 2 None 58 mg/m 2 Autumn 90 mg/m 2 > 239 mg/m 2 None 94 mg/m 2 Nuisance algae Phaeocystis pouchetii Winter/spring 622,000 cells/L > 2,860,000 cells/L None 13,800 cells/L Summer 72 cells/L > 357 cells/L None 408 cells/L, caution level exceedance Autumn 370 cells/L > 2,960 cells/L None Absent Nuisance algae nearfield Pseudo - nitzschia Winter/spring 6,735 cells/L > 17,900 cells/L None 51 cells/L Summer 14,635 cells/L > 43,100 cells/L None 925 cells/L Autumn 10,050 cells/L > 27,500 cells/L None 294 cells/L Nuisance algae nearfield Alexandrium fundyense Any nearfield sample Baseline maximum 163 cells/L > 100 cells/L None 3 cells/L PSP toxin extent NA New incidence None No new incidence *Dissolved oxygen caution and warning levels represent numerical standards, with the caveat “unless background conditions are lower.” Results are therefore compared to the baseline rather than to the caution and warning levels. PSP = paralytic shellfish poisoning NA = not applicable viii Table iii. Contingency Plan threshold values and 2015 results for seafloor monitoring. Parameter Baseline Caution Level Warning Level 2015 Results Sediment parameters RPD depth NA <1.18 cm None 5.51 cm Benthic community parameters Species per sample NA <42.99 or >81.85 None 61.0 Fisher’s log - series alpha NA <9.42 or >15.8 None 13.1 Shannon - Wiener diversity NA <3.37 or >3.99 None 3.93 Pielou’s evenness NA <0.57 or >0.67 None 0.66 % opportunists NA >10% >25% 0.39 % HMW = high molecular weight; LMW = low molecular weight NA = not applicable; RPD = redox potential discontinuity ix Table iv. Contingency Plan threshold values and 2015 result for fish-and-shellfish monitoring.* Parameter Baseline Caution Level Warning Level 2015 Results Flounder disease Liver disease (CHV) 24.4% 44.9% None 10 % Flounder meat PCB 0.033 ppm 1 ppm wet weight 1.6 ppm wet weight 0.0153 ppm Mercury 0.074 ppm 0.5 ppm wet weight 0.8 ppm wet weight 0.0694 ppm Flounder meat , lipid normalize d Chlordane 242 ppb 484 ppb None 19 ppb Dieldrin 63.7 ppb 127 ppb None 0 ppb DDT 775.9 ppb 1552 ppb None 170 ppb Lobster meat PCB 0.015 ppm 1 ppm wet weight 1.6 ppm wet weight 0 . 0121 ppm Mercury 0.148 ppm 0.5 ppm wet weight 0.8 ppm wet weight 0 .102 ppm Lobster meat , lipid normalized Chlordane 75 ppb 150 ppb None 2.3 ppb Dieldrin 161 ppb 322 ppb None 0 ppb DDT 341.3 ppb 683 ppb None 44.8 ppb Mussel tissue PCB 0.011 ppm 1 ppm wet weight 1.6 ppm wet weight 0 .00276 ppm Lead 0.415 ppm 2 ppm wet weight 3 ppm wet weight 0 .147 ppm Mercury 0.019 ppm 0.5 ppm wet weight 0.8 ppm wet weight 0 .00879 ppm Mussel tissue, lipid normalized Chlordane 102.3 ppb 205 ppb None 16.1 ppb Dieldrin 25 ppb 50 ppb None 0 ppb DDT 241.7 ppb 483 ppb None 26.3 ppb PAH 1080 ppb 2160 ppb None 1580 ppb * Exceedances are values greater than (>) all thresholds. CHV = centrotubular hydropic vacuolation 1 1. Introduction Since its creation by the Massachusetts state legislature in 1984, the Massachusetts Water Resources Authority (MWRA) has worked to minimize the effects of municipal wastewater discharge on the marine environment. The mission of what became known as MWRA’s Boston Harbor Project included reducing inflow of contaminants into the waste stream, ending biosolids discharge, improving wastewater-treatment facilities, and providing better dilution of the effluent discharge. Starting during its early years, MWRA conducted environmental monitoring in Boston Harbor, where both biosolids and effluent were discharged, and also in Massachusetts Bay, at what would become the site of a relocated wastewater- effluent discharge. By 2000, most of the Boston Harbor Project had been completed. Biosolids discharges ended in December 1991, all discharges to the southern portion of the harbor ended in 1998, and upgrades to the Deer Island Treatment Plant (DITP) were completed in 1995–2001. A major milestone was reached in September 2000, when all effluent discharge was diverted from Boston Harbor to the deeper, less confined waters of Massachusetts Bay. The relocated outfall operates under a National Pollutant Discharge Elimination System (NPDES) permit, jointly issued by the U.S. Environmental Protection Agency (EPA) and the Massachusetts Department of Environmental Protection (MassDEP). The NPDES permit requires monitoring of effluent and receiving waters to assess compliance with permit conditions and with a permit-required Contingency Plan. Results are presented in annual outfall monitoring overviews, such as this report. Background information about the monitoring program (Werme et al. 2012), the monitoring plan (MWRA 2010), the Contingency Plan (MWRA 2001), past plans and overviews, and area-specific technical reports are available in MWRA’s technical report list, http://www.mwra.state.ma.us/harbor/enquad/trlist.html. This year’s outfall monitoring overview presents results from 2015, marking the twenty-fourth year of Massachusetts Bay monitoring and more than fifteen years of outfall discharge from the deep-water outfall. The report presents information relevant to permit and Contingency Plan conditions in effluent, water-column, seafloor, and fish-and-shellfish parameters, as well as special studies conducted in response to permit conditions and environmental concerns. Data relevant to the Stellwagen Bank National Marine Sanctuary, located offshore from the outfall, are presented in the overview’s water-column and seafloor sections. The report also includes pertinent information from MWRA’s separate monitoring efforts in Boston Harbor. 2 2. Effluent 2015 Characterization The Deer Island Treatment Plant continued to operate as designed through 2015, earning MWRA the National Association of Clean Water Agencies (NACWA) Platinum 9 Peak Performance Award. This NACWA award recognizes facilities with 100% compliance with effluent permit limits over nine consecutive years. The Boston area received almost 10 inches less rain than the long-term average in 2015, one of the driest years since 1990 (Figure 2-1). Consequently, total effluent flow in 2015, 295 million gallons per day, was lower than flows in 2013 or 2014, but about the same as the record low flow of 2012 (Figure 2-2). Virtually all the flow, 99.7%, received full primary and secondary treatment, with only trace discharges of primary-only effluent blended with fully treated effluent prior to discharge in any month (Figure 2-3). Figure 2-1. Annual rainfall in Boston, 1990–2015. Note the lowest rainfall years in 1997, 2001, and 2015. The horizontal line denotes the long-term average. 0 10 20 30 40 50 60 90 91 92 93 94 95 96 97 98 99 00 01 02 03 04 05 06 07 08 09 10 11 12 13 14 15 Rainfall (inches) Rainfall Average 3 Figure 2-2. Annual primary-blended and full secondary effluent flows, 1999–2015. During large storms, flow exceeding the secondary capacity of the plant is diverted around the secondary process to prevent washing out the essential microbes that carry out secondary treatment. These primary-treated flows are then combined (“blended”) with full secondary flows before disinfection and discharge. All 2015 discharges met permit limits. Figure 2-3. Monthly primary-blended and full secondary effluent flows during 2015. 0 50 100 150 200 250 300 350 400 450 500 99 00 01 02 03 04 05 06 07 08 09 10 11 12 13 14 15 Million gallons per day Primary-blended flows Secondary flows 0 50 100 150 200 250 300 350 400 450 500 Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec Million gallons per day Primary-blended flows Secondary flows 4 The total suspended solids load to Massachusetts Bay remained well below the loads discharged to Boston Harbor before the relocated outfall began operation in 2000, 12.4 tons per day, compared to almost 160 tons per day in 1990 and 28.5 tons per day in 2000 (Figure 2-4). Carbonaceous biological oxygen demand, a measure of the amount of oxygen consumed by microorganisms, also remained low, well below levels that would be expected to affect dissolved oxygen at the discharge (not shown). Figure 2-4. Annual solids discharges, 1990–2015. Solids discharges remained low in 2015. (Ending biosolids (sludge) disposal and effluent discharge to the southern portion of the harbor from Nut Island and the implementation of secondary treatment were important steps in the Boston Harbor Project. All effluent discharge was diverted from Boston Harbor to Massachusetts Bay in September 2000.) The total nitrogen load also remained below its threshold in 2015 (Figure 2-5) and was close to the 1999–2015 average. The portion of the load made up of ammonium remained high, as it has since earlier years of the Boston Harbor Project. About 10% of the ammonium in the wastewater influent is removed by secondary treatment, but the biological treatment process converts some organic forms of nitrogen to ammonium. Also, ammonium-rich liquids from the biosolids pelletizing (fertilizer) plant, built as part of the Boston Harbor Project to end biosolids discharge to the harbor, are reintroduced to DITP for treatment, adding to the ammonium load. 0 20 40 60 80 100 120 140 160 180 90 91 92 93 94 95 96 97 98 99 00 01 02 03 04 05 06 07 08 09 10 11 12 13 14 15 Tons per day Sludge Nut Island Deer Island 5 As required by its permit, MWRA continually evaluates nitrogen-removal technologies, so that removal could be quickly implemented, should a need arise (Smolow 2016). Because nitrogen loads have remained below the Contingency Plan caution threshold, and there have been no adverse environmental effects due to nitrogen, nitrogen removal has not been pursued. Figure 2-5. Annual nitrogen discharges, 1999–2015. Most of the nitrogen in the effluent is in the form of ammonium. Metals loads remained low in 2015, with zinc and copper continuing to comprise most of the annual discharges (Figure 2-6). Metals loads are now mostly a factor of rainfall and flow rates rather than variations in inputs to the waste stream. Total discharges in 2015 were about 80 pounds per day, a fraction of what they were before the Boston Harbor Project began, when more than 750 pounds of metals were discharged to Boston Harbor each day. Except for copper, metals meet water quality standards prior to discharge, while copper meets the standard after initial dilution at the Massachusetts Bay outfall. Once considered a sewage tracer, silver is no longer detected in the effluent in appreciable amounts, a result of improved removal efficiencies and the change from film to digital photography. Annual mercury discharges (not shown) are only about 10% of what had been anticipated during the outfall planning process. Most mercury inputs to New England waters now come from atmospheric sources. Polycyclic aromatic hydrocarbon (PAH) and other organic contaminant loads were also much lower than had been anticipated during the outfall planning process. Annual PAH discharges in 2015 were less than 200 pounds per year (Figure 2-7), whereas in 1988, MWRA projected annual discharges would be about 3,100 pounds of total PAHs per year, even with full secondary treatment. 0 3000 6000 9000 12000 15000 99 00 01 02 03 04 05 06 07 08 09 10 11 12 13 14 15 Metric tons per year Caution Threshold Other Nitrogen Species Nitrate/nitrite Ammonium 6 Figure 2-6. Annual metals discharges, 1999–2015. Figure 2-7. Annual PAH discharges, 2006–2015 . LMW PAH = lower molecular weight PAH, HMW PAH = high molecular weight PAH 0 50 100 150 200 250 99 00 01 02 03 04 05 06 07 08 09 10 11 12 13 14 15 Average pounds per day Silver Chromium Lead Nickel Copper Zinc 0 50 100 150 200 250 300 350 400 450 500 2006 2007 2008 2009 2010 2011 2012 2013 2014 2015 Pounds per year LMW PAH HMW PAH 7 Contingency Plan Thresholds There were no permit violations in 2015 and no exceedances of the Contingency Plan effluent thresholds (Table 2-1). Effluent threshold exceedances have been rare throughout the duration of the monitoring program, and none have occurred over the past nine years. Table 2-1. Contingency Plan threshold values and 2015 results for effluent monitorin g. Parameter Caution Level Warning Level 2015 Results pH None <6 or >9 Not exceeded Fecal coliform None > 14,000 fecal coliforms/100 mL Not exceeded Chlorine, residual None > 631 μ g/L daily, > 456 μ g/L monthly Not exceeded Suspended solids None > 45 mg/L weekly > 30 mg/L monthly Not exceeded cBOD None > 40 mg/L weekly, > 25 mg/L monthly Not exceeded Acute toxicity None LC50 <50% Not exceeded Chronic toxicity None NOEC <1.5% effluent Not exceeded PCBs Aroclor > 0.045 ng/L None Not exceeded Plant performance 5 violations/year Compliance <9 5% of the time Not exceeded Flow None >436 MGD average dry days Not exceeded Total nitrogen load > 12,500 mtons/year > 14,000 mtons/year Not exceeded Oil and grease None > 15 mg/L weekly Not exceeded NA = not applicable cBOD = carbonaceous biological oxygen demand LC50 = 50% mortality concentration NOEC = no observable effect concentration PCB = polychlorinated biphenyl Plant performance = compliance with permit conditions 8 3. Water Column The water-column monitoring program evaluates relevant physical-oceanographic processes, water quality, and phytoplankton and zooplankton communities at stations in Massachusetts Bay, at the mouth of Boston Harbor, and in Cape Cod Bay (Figure 3-1). Figure 3-1. Water-column monitoring stations. Also shown are two instrumented buoys, one operated by the Northeastern Regional Association of Coastal and Ocean Observing Systems (NERACOOS) and the other by the National Data Buoy Center (NDBC); the MWRA outfall diffuser; and the Stellwagen Bank National Marine Sanctuary. 9 Sampling during the nine surveys of fourteen stations in 2015 included vertical profiles of physical, chemical, and biological characteristics in the area around the outfall (the nearfield), where some effects of the effluent were expected and have been observed, and at farfield reference stations, including stations in Cape Cod Bay and near the Stellwagen Bank National Marine Sanctuary. Analyses included data from ten additional stations, sampled as part of MWRA’s Boston Harbor water- quality monitoring program when sampling dates were within a few days of the outfall-monitoring surveys. In some years, special surveys are conducted in response to Alexandrium fundyense red tide blooms, but no additional surveys were necessary in 2015. The program continued to benefit from collaboration with the Center for Coastal Studies at Provincetown, Massachusetts, which conducts a monitoring program in Cape Cod Bay. As part of the MWRA monitoring program, the Center for Coastal Studies samples water-column stations in Cape Cod Bay and the Stellwagen Bank National Marine Sanctuary. Regulators have set a target that, whenever possible, sampling in Cape Cod Bay should occur within 48 hours of MWRA Massachusetts Bay sampling and that any failure to meet that schedule should be reported in this annual outfall monitoring overview. In February 2015, ice coverage in Cape Cod Bay delayed sampling until four days after the Massachusetts Bay sampling date. All other sampling was completed within the required time frame. The field monitoring program was augmented by measurements on two instrumented buoys, the Northeastern Regional Association of Coastal and Ocean Observing Systems (NERACOOS) Buoy A01 and the National Oceanic and Atmospheric Administration’s National Data Buoy Center (NDBC) Buoy 44013. The National Aeronautics and Space Administration provided Moderate Resolution Imaging Spectroradiometer (MODIS) satellite imagery for chlorophyll and for sea-surface temperature. Physical Conditions Monitoring has shown that the water quality in the vicinity of the outfall and throughout Massachusetts and Cape Cod bays is heavily influenced by river inflows, weather, and other physical factors. Information about physical conditions has proven key to interpreting the annual monitoring data. Corresponding to the low rainfall in the Boston area in 2015, discharges from the Merrimack and Charles rivers were low throughout much of the year (Figure 3-2; Libby et al. 2016). There were spring peaks in discharge, corresponding to snow melt at the end of winter, but overall, discharges were low. The low flows led to the highest surface- and bottom-water salinities in February through April ever measured by the monitoring program. 10 Figure 3-2. Flows of the Merrimack (top) and Charles (bottom) rivers. Flow from the Charles River was the lowest measured in 24 years of monitoring. Dark red lines are 2015 data. Results from 1992–2014 are in light blue. Surface water temperatures, measured at the NDBC Buoy 44013 and at nearby Station N18, were slightly above average at the beginning of the year, dropping to near the minima for the monitoring program in February and March, and climbing to the monitoring-program maxima by the end of the year (Figure 3-3). Abrupt warming began in May. It was interrupted by a major cooling event at the end of the month, but then continued into the summer. The winter storms promoted very strong downwelling in February (Figure 3-4). Typically moderate upwelling conditions persisted through the summer, with a return to downwelling conditions in the fall. Stratification, the difference in density between surface and bottom waters, began to develop in late April, with the onset of upwelling conditions. Destratification, the re-mixing of the water column that occurs as waters cool in the autumn, was early, the result of downwelling-favorable wind conditions in early October. 11 Figure 3-3. Nearfield surface water temperature at the NDCB Buoy 44013. Surface water temperatures were cold in the early months and warm at the end of 2015. Red line is 2015. Results from 1989–2014 are in blue. Figure 3-4. Average north-south component of wind stress at NDBC Buoy 44013. Winter storms produced the strongest February downwelling conditions ever measured in the monitoring program. Negative values indicate winds from the north, which favor downwelling; positive values indicate winds from the south, which result in upwelling-favorable conditions. Red line is 2015. Results from 1992–2014 are in blue: line is 50 th percentile, dark shading spans 25 th to 75 th percentile, and light shading spans the range. 12 Water Quality Water quality measurements for 2015 included quantification of nutrients, phytoplankton biomass (measured as chlorophyll and particulate organic carbon), and dissolved oxygen. Results continued to confirm predictions of measurable outfall influence in some parameters at stations very near the outfall but no unexpected adverse effects (Libby et al. 2016). At Station N18, located in the nearfield one kilometer south of the outfall, dissolved inorganic nutrient concentrations (nitrate, ammonium, silicate, and phosphate) fell mostly within the ranges seen in previous years (Figure 3-5). During certain of the summer surveys, ammonium concentrations were slightly elevated, at or above the monitoring-program range for those months. Nitrate, silicate, and phosphate concentrations at Station N18 typically show a seasonal pattern of lowered concentrations during the summer. This pattern also occurs in other areas of the bay. Figure 3-5. Depth-averaged dissolved inorganic nutrient concentrations at Station N18, one kilometer south of the outfall, in 2015 compared to prior years. Note difference in scale for phosphate. Red points are results from individual surveys in 2015. Results from 1992–2014 are in blue: line is the 50 th percentile, dark shading spans the 25 th to 75 th percentile, and light shading spans the range. 13 As has been typical since the offshore outfall began to discharge, elevated ammonium concentrations were found in the immediate vicinity of the outfall throughout the year (Figure 3-6). The plume signature could be detected during both stratified and mixed seasons. Ammonium is the largest fraction of the total nitrogen in wastewater and provides a tracer to identify possible effects of the outfall. Figure 3-6. Depth-averaged ammonium concentrations (μM) by station in Massachusetts and Cape Cod bays in 2015. Several panels show additional data from MWRA’s in-house Boston Harbor monitoring surveys when those surveys were within a few days of the outfall-monitoring surveys. 71 o W 48' 36' 24' 12' 70 o W 42 o N 10' 20' 30' 40' 0 2 4 6 8 10 Feb 04 71 o W 48' 36' 24' 12' 70 o W 42 o N 10' 20' 30' 40' 0 2 4 6 8 10 Mar 20 71 o W 48' 36' 24' 12' 70 o W 42 o N 10' 20' 30' 40' 0 2 4 6 8 10 Apr 13 71 o W 48' 36' 24' 12' 70 o W 42 o N 10' 20' 30' 40' 0 2 4 6 8 10 May 11 71 o W 48' 36' 24' 12' 70 o W 42 o N 10' 20' 30' 40' 0 2 4 6 8 10 Jun 23 71 o W 48' 36' 24' 12' 70 o W 42 o N 10' 20' 30' 40' 0 2 4 6 8 10 Jul 21 71 o W 48' 36' 24' 12' 70 o W 42 o N 10' 20' 30' 40' 0 2 4 6 8 10 Aug 18 71 o W 48' 36' 24' 12' 70 o W 42 o N 10' 20' 30' 40' 0 2 4 6 8 10 Sep 09 71 o W 48' 36' 24' 12' 70 o W 42 o N 10' 20' 30' 40' 0 2 4 6 8 10 Oct 21 71 o W 48' 36' 24' 12' 70 o W 42 o N 10' 20' 30' 40' 0 2 4 6 8 10 Aug 18 14 As in previous years, the plume’s ammonium signature was evident in surface waters during the winter and spring (Figure 3-7), but was confined beneath the pycnocline during the summer, stratified season (Figure 3-8). The ammonium signature could be detected only within 10–20 kilometers of the outfall in both well-mixed and stratified seasons, consistent with predictions made during the outfall siting process. Figure 3-7. (Left) Surface- and bottom-water ammonium on April 13, 2015 at the monitoring stations during mixed conditions. (Right) Cross-sections of concentrations throughout the water column along transects connecting selected stations. W E N S 71 o W 48' 36' 24' 12' 70 o W 42 o N 10' 20' 30' 40' 0 2 4 6 8 10 Apr 13 71 o W 48' 36' 24' 12' 70 o W 42 o N 10' 20' 30' 40' 0 2 4 6 8 10 Apr 13 Surface Bottom μM N S W E N S W E 71 o W 48' 36' 24' 12' 70 o W 42 o N 10' 20' 30' 40' 0 2 4 6 8 10 Feb 04 Distance (km) Depth (m) 0 5 10 15 20 25 30 -70 -60 -50 -40 -30 -20 -10 0 0 2 4 6 8 10 F23 N21 N04 F22 Parameter: NH4 Survey: WN153 Date: 13-Apr-2015 Distance (km) Depth (m) 0 5 10 15 20 25 30 35 -35 -30 -25 -20 -15 -10 -5 0 0 2 4 6 8 10 N01 N21 N18 F15 F10 F06 Distance (km) Depth (m) 0 2 4 6 8 10 12 14 16 18 20 -45 -40 -35 -30 -25 -20 -15 -10 -5 0 0 2 4 6 8 10 F13 F15 N07 N04 15 Figure 3-8. (Left) Surface- and bottom-water ammonium on August 18, 2015 at the monitoring stations during stratified conditions. (Right) Cross-sections of concentrations throughout the water column along transects connecting selected stations. No increase in phytoplankton biomass, measured as chlorophyll or particulate organic carbon, was evident at the outfall. Typically, chlorophyll levels in Boston Harbor and the shallower coastal stations of Massachusetts Bay are elevated in summer months, but during summer 2015, areal chlorophyll levels were relatively low throughout the region, especially in the harbor (Figure 3-9). During months when the water column was vertically well mixed, chlorophyll concentrations were slightly greater. Even at Station N18 near the outfall, chlorophyll levels were at the low end of the historic range during most surveys. W E N S 71 o W 48' 36' 24' 12' 70 o W 42 o N 10' 20' 30' 40' 0 2 4 6 8 10 Aug 18 71 o W 48' 36' 24' 12' 70 o W 42 o N 10' 20' 30' 40' 0 2 4 6 8 10 Aug 18 Surface Bottom μM N S W E N S W E 71 o W 48' 36' 24' 12' 70 o W 42 o N 10' 20' 30' 40' 0 2 4 6 8 10 Feb 04 Distance (km) Depth (m) 0 5 10 15 20 25 30 -70 -60 -50 -40 -30 -20 -10 0 0 2 4 6 8 10 F23 N21 N04 F22 Parameter: NH4 Survey: WN157 Date: 18-Aug-2015 Distance (km) Depth (m) 0 5 10 15 20 25 30 35 -35 -30 -25 -20 -15 -10 -5 0 0 2 4 6 8 10 N01 N21 N18 F15 F10 F06 Distance (km) Depth (m) 0 2 4 6 8 10 12 14 16 18 20 -45 -40 -35 -30 -25 -20 -15 -10 -5 0 0 2 4 6 8 10 F13 F15 N07 N04 16 Figure 3-9. Average areal chlorophyll (mg/m 2 ) by station in Massachusetts Bay in 2015. Satellite imagery confirmed that phytoplankton were relatively abundant prior to the February 2015 survey, particularly inshore and in Cape Cod Bay (Figure 3-10), as they had been in November and December of 2014 (not shown). Biomass levels were low in February and into March, then relatively elevated in May, variable through the summer, and relatively elevated in the fall, corresponding to a mixed diatom bloom. 71 o W 48' 36' 24' 12' 70 o W 42 o N 10' 20' 30' 40' 0 40 80 120 160 200 Feb 04 71 o W 48' 36' 24' 12' 70 o W 42 o N 10' 20' 30' 40' 0 40 80 120 160 200 Mar 20 71 o W 48' 36' 24' 12' 70 o W 42 o N 10' 20' 30' 40' 0 40 80 120 160 200 Apr 13 71 o W 48' 36' 24' 12' 70 o W 42 o N 10' 20' 30' 40' 0 40 80 120 160 200 May 11 71 o W 48' 36' 24' 12' 70 o W 42 o N 10' 20' 30' 40' 0 40 80 120 160 200 Jun 23 71 o W 48' 36' 24' 12' 70 o W 42 o N 10' 20' 30' 40' 0 40 80 120 160 200 Jul 21 71 o W 48' 36' 24' 12' 70 o W 42 o N 10' 20' 30' 40' 0 40 80 120 160 200 Aug 18 71 o W 48' 36' 24' 12' 70 o W 42 o N 10' 20' 30' 40' 0 40 80 120 160 200 Sep 09 71 o W 48' 36' 24' 12' 70 o W 42 o N 10' 20' 30' 40' 0 40 80 120 160 200 Oct 21 71 o W 48' 36' 24' 12' 70 o W 42 o N 10' 20' 30' 40' 0 40 80 120 160 200 Mar 20 17 Figure 3-10. Satellite imagery of surface chlorophyll concentrations in 2015. These images, from at NASA satellite, are heavily weather-dependent and do not represent consistent intervals of time. The numbers show the timing of the nine MWRA surveys. 18 Nearfield surface- and bottom-water dissolved oxygen concentrations were at the low end of the historic range in February (Figure 3-11). Levels were typical from the spring to fall, with brief increases in the summer. Early mixing during September re- oxygenated bottom waters. The fall bottom-water oxygen minimum was relatively high in 2015 compared to past years, continuing to show that the effluent discharge has not caused oxygen depletion near the outfall. Figure 3-11. Surface- and bottom-water dissolved oxygen concentrations at nearfield Station N18 in 2015 compared to prior years. Red points are results from individual surveys in 2015. Results from 1992–2014 are in blue: line is the 50 th percentile, dark shading spans the 25 th to 75 th percentile, and light shading spans the range. 19 Phytoplankton Communities Total phytoplankton abundances were low throughout the year and throughout Massachusetts Bay (Figure 3-12), with overall total annual abundance only 56% of the long-term mean (Libby et al. 2016). The typical summer diatoms Skeletonema spp. were present at only 39% of their long-term mean. The low observed abundances were partly due to the timing of the surveys, as the satellite imagery in Figure 3-10, above, suggested peaks occurring between survey dates. Other explanations include weather patterns and zooplankton grazing (see Zooplankton Communities, below). Figure 3-12. Total phytoplankton abundance (million cells per liter) at selected stations in 2015 compared to prior years . Red points and line are results from individual surveys in 2015. Results from 1992–2014 are in blue: line is the 50 th percentile, dark shading spans the 25 th to 75 th percentile, and light shading spans the range. 20 Annual abundance (not shown) of the nuisance species Phaeocystis pouchetii was low compared to most previous years. Winter-spring 2015 nearfield abundance was moderate or low in the nearfield, but for a second consecutive year, summer nearfield abundance exceeded the very low summer Contingency Plan caution threshold (Figure 3-13). As in 2014, the cold winter and spring in the region delayed the onset of the bloom by about a month. The Contingency Plan exceedance was triggered by a single sample during that delayed bloom (see Contingency Plan Thresholds, below). Figure 3-13. Mean nearfield abundance of Phaeocystis pouchetii, 1992–2015 . (Top) Winter-spring. (Bottom) Summer. (No Phaeocystis were detected in years with no symbol.) Note the difference in scales for winter-spring (caution-level threshold of 2.86 million cells per liter) and summer (caution threshold of 357 cells per liter). 1 10 100 1,000 10,000 100,000 1,000,000 10,000,000 Winter-spring Phaeocystis (cells/l) baseline outfall discharge caution threshold 1 10 100 1,000 10,000 100,000 1,000,000 Summer Phaeocystis (cells/l) baseline outfall discharge caution threshold 21 Toxic dinoflagellate Alexandrium fundyense counts were low in 2015 (Figure 3-14). No paralytic shellfish poisoning (PSP) toxicity was measured in Massachusetts Bay or along the coast from Gloucester, Massachusetts to the New Hampshire border. PSP toxicity was noted in New Hampshire and western Maine waters, but the bloom was minor and short-lived. In previous years, when Alexandrium counts in Massachusetts Bay were elevated, cells had been transported into the bay from the north. During 2015, a lack of storms with winds from the northeast in late April and May reduced the chances of Alexandrium cells entering Massachusetts Bay. Figure 3-14. Nearfield abundance of Alexandrium fundyense, 1992–2015. 1 10 100 1,000 10,000 100,000 Alexandrium per sample (Cells/l +1 ) baseline outfall discharge caution threshold 22 Zooplankton Communities Annual abundances of total zooplankton and many dominant species groups in 2015 were high and continued a trend of increased abundances since lows in the mid-2000s (Figure 3-15, Libby et al. 2016). In July, abundances of total zooplankton at some stations were as much as ten times higher than in other years of the monitoring program (Figure 3-16). The high peaks were partially attributable to extremely high abundances of bivalve veligers (larvae) in July and August, particularly in Boston Harbor. At some stations, abundances of a wide variety of copepods, including adults and copepodites of Pseudocalanus spp., Oithona similis , and Calanus finmarchicus , were also at or above previous maxima from June through October (not shown). Figure 3-15. Long-term trend (1998–2015) in nearfield total zooplankton and copepods, derived from a time-series analysis, compared to the multiyear means. Data are from Stations N04 and N18. 23 Figure 3-16. Total zooplankton abundance (1,000 animals per cubic meter) at selected stations in 2015 compared to prior years. Red points are data from individual surveys in 2015. Results from 1992–2014 are in blue: line is 50 th percentile, dark shading spans 25 th to 75 th percentile, and light shading spans the range. Peak values for 2015 exceeding the length of the y-axis maximum of 500,000 were Stations N04 = 630,000; F23 = 2,400,000; N18 = 570,000; F13 = 610,000; and F06 = 700,000 animals per cubic meter. Long-term trend analysis has shown inverse trends in phytoplankton and zooplankton abundances (Figure 3-17). Reasons for the relatively high zooplankton abundances in recent years and the long-term trends in both phytoplankton and zooplankton abundances are not well understood. Increased zooplankton abundance since 2005 may have contributed to the decline in phytoplankton abundance over the same period. Large-scale regional patterns are likely a major factor. 24 Figure 3-17. Long-term trend (1998–2015) in annual total phytoplankton and total zooplankton in the nearfield. Colored dots and lines based on a smoothing window of 15% of the length of the time series (~3.5 years) and black lines on a 25% smoothing window (6 years). Data are from Stations N04 and N18. Stellwagen Bank National Marine Sanctuary The NPDES permit to discharge from DITP into Massachusetts Bay requires annual reporting on results that are relevant to the Stellwagen Bank National Marine Sanctuary. Water-column Station F22 is in Stellwagen Basin, to the northwest of the sanctuary and is considered to be representative of northern, offshore conditions. Ammonium levels have remained low at Station F22 since the outfall began to discharge (see, for example, 2015 results in Figures 3-6, 3-7, and 3-8, above). Levels have also remained low at Station F06 located to the south and offshore. In contrast, increased ammonium levels have been detected in the nearfield, while decreases have been detected at representative harbor and coastal stations. Sampling at Station F22 and data from NERACOOS Buoy A01 (Figure 3-18), as well as satellite imagery (see Figure 3-10, above) detected no unusual chlorophyll levels in offshore regions in 2015. No effects on chlorophyll levels in the offshore were predicted, and none have been measured. Bottom-water dissolved oxygen concentrations at Station F22 were healthy throughout 2015, with survey data showing the typical decline during the stratified season (Figure 3-19). Data from the NERACOOS Buoy A01, located within the sanctuary, documented the return to oxygenated conditions with fall mixing. 10,000 30,000 50,000 70,000 90,000 1,000,000 1,200,000 1,400,000 1,600,000 1,800,000 1990 1995 2000 2005 2010 2015 2020 Total Zooplankton (animals m -3 ) Phytoplankton (cells L -1 ) Trend Total Phyto NF Trend Total Zoo NF 25 Figure 3-18. Chlorophyll measurements at NERACOOS Buoy A01, inside Stellwagen Bank Marine Sanctuary, and at nearby Station F22. Blanks in the time series represent missing data. Figure 3-19. Bottom water dissolved oxygen concentrations at NERACOOS Buoy A01, inside Stellwagen Bank Marine Sanctuary, and at nearby Station F22. The NERACOOS measurement is at 51 m, the deep Station F22 at 54 m, and the near-bottom Station F22 at 78 m. DO = dissolved oxygen 0 5 10 15 20 Chlorophyll fluorescence (μg/l) NERACOOS Buoy A01 (3 m) WC station F22 near Buoy A01 5 6 7 8 9 10 11 12 Oxygen concentration (mg/l) NERACOOS Buoy A01 (51 m) Deep DO station F22 (51 m) Near-bottom DO station F22 (77 m) 26 Boston Harbor Water quality in Boston Harbor has improved during the past 20 years, and those improvements were sustained in 2015. MWRA’s in-house Boston Harbor monitoring program confirmed that harbor-wide concentrations of total nitrogen and phosphorus remained low, as they have since discharges to the harbor ended (Taylor 2016). Perhaps the most dramatic improvement in Boston Harbor has been the decrease in ammonium levels (Figure 3-20, top; Libby et al. 2016). Ammonium concentrations dropped precipitously when the effluent discharge was diverted from the harbor to Massachusetts Bay in 2000 and have remained low. In 2015, ammonium levels at Station F23, at the harbor mouth, were typical for the post-diversion years. In contrast, ammonium levels have increased at stations closest to the Massachusetts Bay outfall, such as Station N18 (Figure 3-20, bottom). However, because of increased dilution at the offshore outfall, those increases have been substantially smaller than the concurrent decreases in ammonium concentrations in the harbor. While total zooplankton abundance peaked in June and July in Massachusetts Bay, in Boston Harbor, there was one major peak in July. Acartia spp., which are common in the lower-salinity waters found in the harbor, peaked once in June–July and a second time in September at Station F23 at the mouth of the harbor (Figure 3-21). Prior to the outfall diversion, Acartia spp. peak abundances usually occurred in August and September, and since then, peaks have occurred earlier. Overall abundance of Acartia spp. in 2015 was about twice that in 2014. 27 Figure 3-20. (Top) Depth-averaged ammonium levels at Station F23 in Boston Harbor. (Bottom) Depth-averaged ammonium levels at Station N18 near the Massachusetts Bay outfall. Black line shows 2015 results. Red line and shading show data from Boston Harbor discharge years. Blue line and shading show data from Massachusetts Bay discharge years. Lines are the 50 th percentile; dark shading spans the 25 th to 75 th percentile; light shading spans the range. 28 Figure 3-21. Acartia spp. abundance at Station F23 in Boston Harbor in 2015 compared to prior years. Red points are results from individual surveys in 2015. Results from 1992–2014 are in blue: line is the 50 th percentile, dark shading spans the 25 th to 75 th percentile, and light shading spans the range. Contingency Plan Thresholds All water-quality parameters were within normal ranges during 2015. There was one Contingency Plan caution-level threshold exceedance for a nuisance algae measure, summer Phaeocystis pouchetii abundance (Table 3-1). A delay in the spring Phaeocystis population increase, caused by cold March and April water temperatures, was responsible for the exceedance. A summer Phaeocystis caution level exceedance was also observed during 2014. Neither year’s exceedance caused measurable aesthetic or other adverse effects. 29 Table 3-1. Contingency Plan threshold values and 2015 results for water-column monitoring . Parameter Baseline Caution Level Warning Level 2015 Results Dissolved oxygen* Nearfield concentration 6.05 mg/L < 6.5 mg/L < 6.0 mg/L 7.56 mg/L Nearfield percent saturation 65.3% < 80% < 75% 84.5 % Stellwagen concentration 6.23 mg/L < 6.5 mg/L < 6.0 mg/L 7.44 mg/L Stellwagen percent saturation 67.2% < 80 < 75% 79.6 % Nearfield depletion rate 0.024 mg/L/d > 0.037 mg/L/d > 0.049 mg/L/d 0.018 mg/L/d Chlorophyll Annual 72 mg/m 2 > 108 mg/m 2 > 144 mg/m 2 87 mg/m 2 Winter/spring 50 mg/m 2 > 199 mg/m 2 None 122 mg/m 2 Summer 51 mg/m 2 > 89 mg/m 2 None 58 mg/m 2 Autumn 90 mg/m 2 > 239 mg/m 2 None 94 mg/m 2 Nuisance algae Phaeocystis pouchetii Winter/spring 622,000 cells/L > 2,860,000 cells/L None 13,800 cells/L Summer 72 cells/L > 357 cells/L None 408 cells/L, caution level exceedance Autumn 370 cells/L > 2,960 cells/L None Absent Nuisance algae nearfield Pseudo - nitzschia Winter/spring 6,735 cells/L > 17,900 cells/L None 51 cells/L Summer 14,635 cells/L > 43,100 cells/L None 925 cells/L Autumn 10,050 cells/L > 27,500 cells/L None 294 cells/L Nuisance algae nearfield Alexandrium fundyense Any nearfield sample Baseline maximum 163 cells/L > 100 cells/L None 3 cells/L PSP toxin extent NA New incidence None No new incidence *Dissolved oxygen caution and warning levels represent numerical standards, with the caveat “unless background conditions are lower.” Results are therefore compared to the baseline rather than to the caution and warning levels. PSP = paralytic shellfish poisoning NA = not applicable 30 4. Sea Floor Seafloor monitoring in 2015 included sampling and analysis of soft-bottom sediment conditions, tracers, and infauna at 14 stations and sediment-profile imaging at 23 stations (Figures 4-1, 4-2). Figure 4-1. Soft-bottom monitoring stations. Benthic community parameters and sediment characteristics are measured in samples from 14 stations. Also shown are the instrumented buoys, the MWRA outfall diffuser, and the Stellwagen Bank National Marine Sanctuary. 31 Figure 4-2. Sediment-profile imaging stations. Images are taken at 23 stations and provide rapid assessments of benthic habitats. Also shown are the NDBC buoy and the MWRA outfall diffuser. SPI = sediment-profile imaging 32 Soft-bottom sediment sampling was completed over two days in early August 2015, with samples analyzed for grain-size distribution, total organic carbon, the effluent tracer Clostridium perfringens spores, and benthic infauna. The 14 stations included one station in the “transition” area, located between Boston Harbor and the nearfield stations (FF12); four nearfield stations located within two kilometers of the outfall (NF13, NF14, NF17, NF24); six nearfield stations located within Massachusetts Bay but farther than two kilometers from the outfall (NF04, NF10, NF12, NF20, NF21, NF22); and three farfield reference stations located in Massachusetts Bay and Cape Cod Bay (FF01A, FF04, and FF09). For the purposes of threshold testing, “nearfield” includes the transition station, as well as both nearfield groups, for a total of eleven stations. Sediment-profile imaging was also completed in August. Triplicate images from 23 stations were used to measure the apparent reduction-oxidation (redox) potential discontinuity (RPD) depth, apparent successional stage of the community, and an organism-sediment index which is derived from the RPD depth and the successional stage. Sediment Characteristics and Tracers Sediment grain-size distributions in 2015 varied broadly among stations, ranging from silt and clay at some stations to mostly sand at others (Nestler et al. 2016). Sediment grain-size distributions have remained generally consistent at individual stations over the years of the monitoring program. Changes that have occurred over time have been mostly associated with large storms, with wave-driven currents sufficient to re-suspend bottom sediments. There were some storm-related changes in 2015, but those changes were reflected more in the imaging portion of the monitoring program than in the grab samples (see Sediment-profile Imaging, below). Percent organic carbon content, which tracks closely with fine material in the samples, was consistent with past results at most stations, with higher mean total organic carbon concentrations at stations with finer sediments. Total organic carbon concentrations showed no signs of organic enrichment from the effluent discharge, even at stations closest to the outfall. As in past years since the offshore outfall began to discharge (except 2006), it was possible to detect elevated levels of Clostridium perfringens spores at the stations located closest to the outfall (Figures 4-3 and 4-4). Past years’ statistical analyses have shown that these increases close to the outfall are statistically significant and consistent with predictions made during the outfall siting process. 33 Figure 4-3. Concentrations of Clostridium perfringens spores, corrected for sediment grain size, in 2015. Figure 4-4. Mean concentrations of Clostridium perfringens spores during the baseline and outfall discharge years. Tran = transition area, stations located between Boston Harbor and the outfall; NF<2km = nearfield stations located within 2 km of the outfall diffusers; NF>2km = nearfield stations located further than 2 km from the diffusers; FF = farfield stations offshore from the outfall Clostridium perfringens (cfu/g dry/%fines) 0 50 100 150 200 250 300 350 Outfall Startup 1991 1993 1995 1997 1999 2001 2003 2005 2007 2009 2011 2013 2015 Tran NF <2km NF >2km FF 34 Soft-bottom Communities The 14 soft-bottom samples collected and analyzed in 2015 yielded 20,341 organisms, classified into 164 species and 22 other discrete taxonomic groups (Nestler et al. 2016). In recent years, infaunal abundance has been at the lower end of the range observed over the monitoring program, but it was higher in 2014 and 2015 than in 2011 and 2013, particularly in the transition area (Figure 4-5). Figure 4-5. Mean infaunal abundance per sample in four areas of Massachusetts Bay, 1992–2015. Tran = transition area, stations located between Boston Harbor and Massachusetts Bay; NF<2km = stations within 2 km of the outfall; NF>2km = nearfield stations greater than 2 km from the outfall; FF = farfield stations offshore from the outfall Total Abundance 0 500 1000 1500 2000 2500 3000 3500 4000 4500 Outfall Startup 1991 1993 1995 1997 1999 2001 2003 2005 2007 2009 2011 2013 2015 Tran NF <2km NF >2km FF 35 A series of multivariate analyses assessed spatial and temporal patterns in the soft- bottom benthic communities and found no particular species or type of community that could be specifically associated with the outfall. As in past years, a cluster analysis identified two main infaunal assemblages, with an outlier at Station FF04, which is offshore in Stellwagen Basin and has consistently had a distinct community. Also continuing the pattern of past years, an ordination analysis demonstrated that variations in species distributions largely followed differences in sediment type (Figure 4-6). The multivariate analyses have shown no indication of any relation of species composition to proximity to the outfall. Figure 4-6. Percent fine sediments superimposed on the ordination plot of the 2015 infauna samples. Each point on the plot represents one of the 14 stations; similarity of species composition is indicated by proximity of points on the plot. Faunal assemblages (Groups I-II, and sub-groups) identified by cluster analysis are circled on the plot. Sediment-profile Imaging Sediment-profile images continued to show no adverse effects of the outfall (Nestler et al. 2016). Images from five of the 23 nearfield stations appeared to be sandier, with coarser-grained sediments, than in 2014, consistent with storm-induced sediment redistributions (Figure 4-7). The images also showed an increase in surface features indicative of physical structuring of the sediments at some stations. Storms with winds strong enough to re-suspend sediments occurred in October 2014 and February, March, and June 2015. 36 Figure 4-7. Apparent change in sediment grain-size distribution between 2014 and 2015 at Stations NF02 and NF17. Station NF02 is more than 5 km to the southwest of the outfall and changed from fine sand and silt to medium sand; NF17 is immediately to the southwest of the outfall and changed from fine-medium sand to medium sand. The average RPD depth (the depth to which oxygen penetrates into sediments as determined by color changes) was the deepest ever measured during the monitoring program (Figure 4-8). At 14 of the 23 stations, the RPD was deeper than the bottom of the images. The environmental concern before the outfall began operation was that the RPD depth would become shallower, due to increases in sediment organic matter causing stress on sensitive sediment-dwelling organisms. A deeper RPD depth continued to indicate that there has been no adverse effect from the discharge. 37 Figure 4-8. Annual apparent color RPD depth for data from nearfield stations. The average RPD discharge-period mean has been deeper than the baseline mean, continuing to indicate that there has been no adverse effect from the discharge. Secondary treatment effectively reduces contaminants that might affect the sediments, and monitoring has shown that physical processes, such as storms and storm-induced sediment transport, are the primary stressors on the Massachusetts Bay sea floor. The dominance of physical forces may be considered typical of outfalls that have been located in high-energy areas that promote rapid dispersion of the effluent discharge. Counterintuitively, the camera images detected a trend beginning in 2013 towards increased numbers of “pioneering” or “Stage I” organisms. This finding would be unexpected where there are deepening RPD depths. It was also not anticipated from the infaunal organism analyses presented above, either from the identification of individual animals or from the diversity and other community-parameter measurements. The change appears to be related to a slight coarsening of sediment grain-size and a resulting decline in visible biogenic structures in the sediment-profile images, a factor in determining successional stage. -8 -7 -6 -5 -4 -3 -2 -1 0 RPD (cm) Mean RPD Depth +/- 1SD Outfall Startup Threshold 38 Sediment-profile imaging and community analyses have been used to investigate effects of numerous coastal ocean effluent outfalls around the world (Puente and Diaz 2015). Those studies have found that, in general, outfalls that are dominated by high- energy physical processes, with little accumulation of organic matter, such as the MWRA outfall, have low or no detectable adverse effects on benthic infauna. Adverse effects on the bottom communities, where they do occur, are manifested primarily as changes in the ratio of opportunistic to sensitive species and as decreases in diversity or species richness (Figure 4-9). Opportunistic species remain rare in Massachusetts Bay, and any changes in diversity measures have been increases rather than the decreases typical of responses to adverse conditions. Changes, when they have been detected, have been analyzed and are thought to represent normal variation for the region. Figure 4-9. Numbers of studies showing types of adverse effects on benthic communities observed in studies of effluent outfalls on coastal and ocean communities. The graph is based on data from 44 outfalls around the world (redrawn from Puente and Diaz 2015). 39 Stellwagen Bank National Marine Sanctuary The NPDES permit to discharge from DITP into Massachusetts Bay requires annual reports on results that are relevant to the Stellwagen Bank National Marine Sanctuary. MWRA’s deepwater reference Station FF04 lies within the depositional part of the sanctuary, in Stellwagen Basin, where long-term accumulation of pollutants and their effects could be detected if they were to occur. Station FF04 is typical of the deep waters offshore from the outfall, representative of a number of stations monitored in earlier years of the monitoring program, and it continues to support an infaunal community typical of what was found at the larger suite of deepwater stations. The deepwater stations, including Station FF04, have always shown distinct differences from those found at shallower stations, probably due to their depth, their fine-grained sediments, and their distance from shore. Superimposing depth on the ordination plot for 2015 infauna samples continued to show these differences (Figure 4-10; see also Figure 4-6, which superimposed percent fine sediments on the ordination plot). Figure 4-10. Depth superimposed on the ordination plot of the 2015 infauna samples. Each point on the plot represents one of the 14 stations; similarity of species composition is indicated by proximity of points on the plot. Faunal assemblages (Groups I-II, and sub-groups) identified by cluster analysis are circled on the plot. 40 Boston Harbor While the chemistry and biology of the Massachusetts Bay sea floor have not been affected by the relocated outfall, conditions have greatly improved and continue to improve in Boston Harbor as a result of the Boston Harbor Project and more recent enhancements to treatment and remediation of combined sewer overflows. MWRA has conducted ongoing seafloor monitoring in Boston Harbor since 1991. Annual sediment and infauna samples are taken from nine stations (Figure 4-11). Figure 4-11. Soft-bottom sampling stations in Boston Harbor. Nine stations are sampled each year for sediment characteristics and infauna analyses. Concentrations of total organic carbon (not shown) and Clostridium perfringens spores (Figure 4-12) have declined over time. Infaunal diversity has increased, reflecting continued improvement in habitat conditions. An ordination plot of Boston Harbor infaunal samples shows a separate community in stations in the outer harbor and a most unique fauna at Station T04 at the mouth of Savin Hill Cove, a location recognized as one of the most polluted sites in the harbor (Figure 4-13). Sediment- profile imaging also confirmed an inner- to outer-harbor gradient. 41 Figure 4-12. Mean concentrations of Clostridium perfringens spores at selected harbor stations, 1991–2015. Figure 4-13. Ordination plot of 2015 Boston Harbor infauna samples. Group I comprises stations from the outer harbor; Group II includes Station C019 in the inner harbor and Station T07 in Quincy Bay. The assemblage most different from others was found at Station T04, at the mouth of Savin Hill Cove, in Dorchester Bay. Clostridium perfringens (cfu/g dry/%fines) 0 100 200 300 400 500 600 700 800 900 1000 1100 1991 1993 1995 1997 1999 2001 2003 2005 2007 2009 2011 2013 2015 T01 T02 T04 T08 C019 42 Contingency Plan Thresholds There were no seafloor Contingency Plan threshold exceedances in 2015 (Table 4-1). Values for Shannon-Wiener diversity and Pielou’s evenness, both diversity measures that triggered exceedances in 2010–2014, remained high but were within the upper caution-level ranges (Figure 4-14). Two other community threshold parameters, total number of species per sample (species richness) and Fisher’s log-series alpha, another diversity measure, were also within the caution-level ranges. There has been no indication, even when diversity levels exceeded the upper bounds of the caution-level thresholds, that environmental conditions had worsened or that there had been any effect of the outfall. Percent opportunists among the soft-bottom community remained far below caution and warning levels. Table 4-1. Contingency Plan threshold values and 2015 results for seafloor monitoring. Parameter Baseline Caution Level Warning Level 2015 Results Sediment parameters RPD depth NA <1.18 cm None 5.51 cm Benthic community parameters Species per sample NA <42.99 or >81.85 None 61.0 Fisher’s l og - series alpha NA <9.42 or >15.8 None 13.1 Shannon - Wiener diversity NA <3.37 or >3.99 None 3.93 Pielou’s evenness NA <0.57 or >0.67 None 0.66 % opportunists NA >10% >25% 0.39 % HMW = high molecular weight; LMW = low molecular weight NA = not applicable; RPD = redox potential discontinuity 43 Figure 4-14. Annual community parameters with nearfield Contingency Plan thresholds. The varied symbols represent differences in the stations sampled over the years of the program. Results were tested against thresholds calculated for each sampling design, but only the current threshold values are shown. Except for the percent opportunists threshold, which is based on levels in Boston Harbor, thresholds have both upper and lower bounds to show potentially meaningful changes from the baseline. SD = standard deviation 30 50 70 90 Total species richness 6 10 14 18 Log-series alpha 2.5 3.0 3.5 4.0 4.5 5.0 Shannon-Wiener diversity 0.4 0.5 0.6 0.7 0.8 Pielou's evenness 0 4 8 12 Percent opportunists 0.40 0.45 0.50 0.55 0.60 0.65 0.70 0.75 0.80 Evenness (J) Baseline mean Thresholds Mean +/-1SD Outfall startup 44 5. F ish and Shellfish Each year MWRA monitors the health of winter flounder from the Massachusetts Bay outfall site, Deer Island Flats in Boston Harbor, off Nantasket Beach just outside the harbor, and eastern Cape Cod Bay. Every three years, including 2015, monitoring includes chemistry measurements in flounder fillets and liver, lobster meat and hepatopancreas, and cage-deployed blue mussels. Lobsters are sampled from Deer Island Flats, the outfall site, and Cape Cod Bay. Mussels are deployed at two sites near the outfall, at Deer Island Light, and in Boston’s inner harbor (Figure 5-1) Figure 5-1. Fish-and-shellfish monitoring stations. Also shown are the two instrumented buoys, the MWRA outfall diffuser, and the boundaries of the Stellwagen Bank National Marine Sanctuary. 45 Flounder Health Annual flounder monitoring focuses on the presence of early liver disease and liver neoplasia (tumors). Other indications of health are also documented. In April–May 2015, 50 sexually mature flounder were collected from Deer Island Flats, off Nantasket Beach, the outfall site, and eastern Cape Cod Bay (Moore et al. 2016). Catch per unit effort, which has varied through time, was highest at eastern Cape Cod Bay and the outfall site and lowest at Deer Island Flats and off Nantasket Beach. Abandoned fishing gear, sometimes referred to as “ghost gear,” continued to interfere with catches, particularly in muddy depressions at the outfall and at Deer Island Flats. Mean ages of fish ranged from 4.1 to 5.0 years across the sites, younger than samples from 2014, but well within the range for the monitoring program. Similar to 2014, lengths and weights were somewhat lower than typically observed but remained within historic ranges at all sites. As has been common throughout the duration of the monitoring program, the catches were dominated by females. (Additional information on flounder sex ratios is presented in Section 6, Special Studies.) Measures of external condition, such as fin erosion and blind-side ulcers, also fell within historic ranges. Prevalence of fin erosion, a condition that can be indicative of elevated concentrations of ammonium and other pollutants, ranged from a low of 4% near the outfall to a high of 22% off Nantasket Beach. Blind-side ulcers, which were first noted in 2003, were rare in 2015, ranging from a low of zero in eastern Cape Cod Bay to a high of 4% in fish from Deer Island Flats. There were elevated occurrences of ulcers in 2003–2006 and again in 2011. The pathology of the ulcers has been studied but is not well understood. The incidence of centrotubular hydropic vacuolation (CHV), a mild condition associated with exposure to contaminants and a neoplasia precursor, remained lower than the baseline observations. Incidence of CHV at the outfall was about the same as in 2014 (Figure 5-2). Average severity of CHV (not shown) also remained lower than baseline levels. Fish from Deer Island Flats, near the former Boston Harbor outfall, showed an increase in CHV occurrence to 32%, but incidence remained lower than during the 1980s, when it was 75% or more. 46 Figure 5-2. Annual prevalence of centrotubular hydropic vacuolation (CHV), 1991–2015. DIF = Deer Island Flats, ECCB = Eastern Cape Cod Bay, NB = Nantasket Beach, OS = Outfall Site No liver tumors were observed in any fish from any site. Incidence of neoplasia has been rare throughout the area since MWRA monitoring started in 1991, although levels were higher in flounder taken from Boston Harbor for studies during the 1980s. Neoplasia has never been observed in a fish taken from the vicinity of the outfall. CHV Prevalence (%) 0 10 20 30 40 50 60 70 Outfall Startup 1991 1993 1995 1997 1999 2001 2003 2005 2007 2009 2011 2013 2015 DIF ECCB NB OS 47 Fish and Shellfish Chemistry Samples for chemical analyses of winter flounder tissues were taken from the same April collections made for the health assessments. Samples of winter flounder fillet from each site were analyzed for PCBs, pesticides, and mercury. Liver samples from the same fish were analyzed for PCBs, pesticides, PAHs, and selected metals. Lobsters were collected by local lobstermen in September and October, later than in other years. Samples of lobster meat from each site were analyzed for PCBs, pesticides, and mercury. Hepatopancreas (tomalley) samples from the same animals were analyzed for PCBs, pesticides, PAHs, and selected metals. Over the years of the monitoring program, mussels have been collected in June from a reference location and deployed in cages for 45 and 60 days, ending in late August. Wild mussels were not available in 2015, so they were obtained from a commercial aquaculture facility in Blue Hill Bay, Maine. The commercial mussels had much thinner shells than the wild mussels deployed in the past and were apparently less hardy, as unusually low survival rates were observed, particularly at the inner harbor site. Survival rates were highest in the offshore deployments, including the outfall site. Reduced survival among the cage-deployed mussels limited the number of replicate samples that could be analyzed at some sites. There were, however, sufficient data to compare results across sites and years. Mussel tissues were analyzed for PCBs, pesticides, PAHs, mercury, and lead. Overall, concentrations of banned organochlorine pesticides and PCBs remained low in all flounder fillet and liver, lobster meat and hepatopancreas, and deployed-mussel samples, with the highest concentrations found in samples from near Deer Island, the site of the former Boston Harbor outfall, and lowest in samples from Cape Cod Bay (Nestler et al. 2016). Slow declines in banned pesticides and PCBs continued across all samples types and locations and were particularly evident in samples taken near Deer Island (for example, Figures 5-3 and 5-4, which show total chlordane in flounder fillet and lobster meat). In fish and shellfish samples taken at the outfall site, concentrations of many organic compounds were the lowest measured throughout the duration of monitoring. 48 Figure 5-3. Total chlordane in flounder fillets, 1995–2015. Long-term declines in concentrations of banned organochlorine pesticides and PCBs were seen across sample types and locations. DIF = Deer Island Flats, ECCB = Eastern Cape Cod Bay, NB = Nantasket Beach, OS = Outfall Site Figure 5-4. Total chlordane in lobster meat, 1994–2015. DIF = Deer Island Flats, ECCB = Eastern Cape Cod Bay, OS = Outfall Site ng/g dry weight 0 5 10 15 20 Outfall Startup 1995 1996 1997 1998 1999 2000 2001 2002 2003 2006 2009 2012 2015 DIF ECCB NB OS ng/g dry weight 0.0 1.0 2.0 3.0 4.0 5.0 6.0 7.0 8.0 Outfall Startup 1994 1995 1996 1997 1998 1999 2000 2001 2002 2003 2006 2009 2012 2015 DIF ECCB OS 49 There has also been evidence of long-term declines in PAHs near Deer Island. Low molecular weight PAH concentrations were at or near monitoring-program lows in deployed mussels from all sites in 2015 (Figure 5-5). High molecular weight PAH concentrations (not shown) were slightly higher than those measured in 2012, but well below levels observed in the mid-1990s. Figure 5-5. Low molecular weight PAHs in deployed mussels, 1991–2015. DIL = Deer Island Light, LNB = near the outfall, 1 kilometer south of the risers, OSM = Outfall Site Unlike organic compounds, concentrations of metals in flounder, lobsters, and mussels have often been highest at the outfall site, even during the baseline period. Individual metals show varied temporal trends and sometimes no trend at all. Concentrations of silver, once considered a sewage indicator, have decreased in, for example, flounder livers from the outfall site (Figure 5-6), but concentrations of nickel (not shown) suggest a possible region-wide increase in concentrations. Overall, lead levels have declined throughout the region since the early 1990s, when pre-deployment mussels often had lead concentrations higher than post-deployment mussels from the outfall site (Figure 5-7). ng/g dry weight 0 100 200 300 400 500 600 700 Outfall Startup 1991 1992 1993 1994 1995 1996 1997 1998 1999 2000 2001 2002 2003 2006 2009 2012 2015 DIL LNB OSM 50 Figure 5-6. Silver in flounder livers, 1995–2015. DIF = Deer Island Flats, ECCB = Eastern Cape Cod Bay, NB = Nantasket Beach, OS = Outfall Site Figure 5-7. Lead in deployed mussels, 1991–2015 . Gaps in data indicate years when concentrations in deployed mussels were lower than the pre-deployment controls. DIL = Deer Island Light, LNB = near the outfall, 1 kilometer south of the risers, OSM = Outfall Site μg/g dry weight 0.0 5.0 10.0 15.0 20.0 25.0 30.0 Outfall Startup 1995 1996 1997 1998 1999 2000 2001 2002 2003 2006 2009 2012 2015 DIF ECCB NB OS μg/g dry weight 0.0 2.0 4.0 6.0 8.0 10.0 12.0 Outfall Startup 1991 1992 1993 1994 1995 1996 1997 1998 1999 2000 2001 2002 2003 2006 2009 2012 2015 DIL LNB OSM 51 Contingency Plan Thresholds There were no Contingency Plan threshold exceedances for fish and shellfish in 2015 (Table 5-1). Incidence of CHV, the most common indicator of liver disease in the winter flounder of the region, was 10% in fish taken from the vicinity of the outfall, lower than the 44.9% caution threshold and the 24.4% baseline average. Contaminant levels in flounder, lobster, and mussel tissues were also well below caution and warning thresholds. Table 5-1. Contingency Plan threshold values and 2015 result for fish-and-shellfish monitoring. * Parameter Baseline Caution Level Warning Level 2015 Results Flounder disease Liver disease (CHV) 24.4% 44.9% None 10 % Flounder meat PCB 0.033 ppm 1 ppm wet weight 1.6 ppm wet weight 0.0153 ppm Mercury 0.074 ppm 0.5 ppm wet weight 0.8 ppm wet weight 0.0694 ppm Flounder meat , lipid normalized Chlordane 242 ppb 484 ppb None 19 ppb Dieldrin 63.7 ppb 127 ppb None 0 ppb DDT 775.9 ppb 1552 ppb None 170 ppb Lobster meat PCB 0.015 ppm 1 ppm wet weight 1.6 ppm wet weight 0.0121 ppm Mercury 0.148 ppm 0.5 ppm wet weight 0.8 ppm wet weight 0.102 ppm Lobster meat , lipid normalized Chlordane 75 ppb 150 ppb None 2.3 ppb Dieldrin 161 ppb 322 ppb None 0 ppb DDT 341.3 ppb 683 ppb None 44.8 ppb Mussel tissue PCB 0.011 ppm 1 ppm wet weight 1.6 ppm wet weight 0.00276 ppm Lead 0.415 ppm 2 ppm wet weight 3 ppm wet weight 0.147 ppm Mercury 0.019 ppm 0.5 ppm wet weight 0.8 ppm wet weight 0.00879 ppm Mussel tissue, lipid normalized Chlordane 102.3 ppb 205 ppb None 16.1 ppb Dieldrin 25 ppb 50 ppb None 0 ppb DDT 241.7 ppb 483 ppb None 26.3 ppb PAH 1080 ppb 2160 ppb None 1580 ppb * Exceedances are values greater than (>) all thresholds. CHV = centrotubular hydropic vacuolation 52 6. Special Studies Besides monitoring the effluent and the water column, sea floor, and fish and shellfish in Massachusetts Bay and the surrounding area, MWRA conducts special studies in response to specific permit requirements, scientific questions, and public concerns. This year’s overview focuses on eelgrass in Boston Harbor, bacterial water quality in Massachusetts Bay, winter flounder sex ratios, and ongoing monitoring by the Center for Coastal Studies in Cape Cod Bay. Eelgrass in Boston Harbor Historically, seagrasses, primarily eelgrass ( Zostera marina ), were prevalent in Boston Harbor, providing refuge and foraging habitat for marine animals, including commercial fish and shellfish. Over the past century, the health and extent of eelgrass beds declined, partly for reasons that affected sea grass beds globally and partly due to local changes in environmental conditions. Excess nutrients from sewage and fertilizers and other factors that lead to corresponding decreases in water clarity have been important factors in seagrass declines. The change in nutrient regime in Boston Harbor provides some encouragement that excess nutrients no longer preclude re-establishment and maintenance of eelgrass beds. Once very high, about 800 kg per hectare per year, nitrogen loading to the harbor is now well below 150 kg per hectare per year (Figure 6-1). This value represents a maximum threshold thought to allow for eelgrass beds in southern New England (Latimer and Rego 2010). 53 Figure 6-1. Percent eelgrass coverage vs. nitrogen loading in coastal systems compared to Boston Harbor before and after the Boston Harbor Project. The vertical blue line represents the 150 kg per hectare per year loading thought to allow for eelgrass beds in southern New England. Since 2008, sediment-profile imagery in MWRA’s in-house harbor-monitoring program has recorded eelgrass at Deer Island Flats, an area that some had thought was too degraded for colonization and restoration of seagrass beds. The MassDEP Eelgrass Mapping and Monitoring Program has documented eelgrass expansion in the north region of the harbor between 1995 and 2012 (Figure 6-2). This region once received the bulk of the harbor’s elevated nitrogen inputs. Over the entire geographic extent of the harbor, however, eelgrass restoration remains a challenge. Other factors that affect turbidity may now be limiting seagrasses in the harbor. 54 Figure 6-2. Eelgrass ( Zostera marina ) coverage in the north harbor, 1995–2012. (Data from MassDEP.) Bacterial Water Quality in Boston Harbor and Massachusetts Bay Before the Boston Harbor Project, bacterial pollution from untreated combined sewer overflows (CSOs), incompletely treated primary wastewater effluent, and daily discharge of digested sewage sludge (biosolids) resulted in widespread beach closures and violations of bacterial water-quality standards throughout the harbor. Degraded water quality from bacterial pollution was one of the main drivers behind the creation of MWRA and the court-ordered Boston Harbor Project. Before 1991, wet-weather exceedances of water-quality standards were common and severe, with many parts of Boston Harbor exceeding the Enterococcus bacteria swimming standard (35 colonies/100 ml), sometimes by a factor of five or more (Figure 6-3, left). Since 2007, after the completion of DITP and most CSO projects, water quality in most of Boston Harbor and its tributaries meets the Enterococcus standard, even in wet weather (Figure 6-3, right). Remaining wet-weather Enterococcus exceedances occur in smaller areas and are less severe. 55 Figure 6-3. Bacterial water quality prior to the Boston Harbor Project and after completion of the treatment plant and most CSO projects. The improvements in Boston Harbor have not been accompanied by any degradation to Massachusetts Bay. Since 1999, MWRA has monitored sewage-indicator bacteria ( Enterococcus and fecal coliform bacteria) in the vicinity of the Massachusetts Bay outfall (Codiga et al. 2016). The surveys address permit conditions that the discharge meet the state water quality standard for primary-contact recreation and that it not adversely affect shellfishing resources. Monitoring includes monthly surveys at 11 stations (Figure 6-4) and additional surveys of those same stations if triggered by a possibly adverse condition at DITP, such as an extended chlorination failure or a long period of blending primary-only treated effluent with effluent that has received full primary and secondary treatment. Prior to Boston Harbor projects (1989-1991) Most Boston Harbor projects complete (post-2007) 56 Figure 6-4. Stations monitored for sewage-indicator bacteria and the outfall diffuser. Sampling and analysis assess water quality directly over the outfall, other locations in the outfall nearfield, and near the coastline, between the outfall and active shellfish beds. Enterococcus analyses determine whether waters near the outfall meet the standard for contact recreation (swimming). Fecal coliform bacteria counts determine whether waters meet the standard for shellfishing. Results show that, annually, throughout the duration of monitoring, levels have remained well below the swimming standard, a geometric mean of 35 Enterococcus per 100 ml, at all areas (Figure 6-5). Similarly, fecal coliform bacteria counts have remained well below the standard for shellfishing, 14 fecal coliforms per 100 ml (Figure 6-6). Of the more than 3,000 samples analyzed in 1999–2014 (the most recent year included in the analyses), the vast majority of samples had undetectable levels of sewage-indicator bacteria. Even beneath the pycnocline under stratified conditions, when dilution is minimized, 90% of the Enterococcus samples and 80% of the fecal coliform samples had undetectable levels of indicator bacteria. Further, sampling in response to adverse conditions detected only minor differences from the routine, monthly samples, and conditions at outfall stations were largely indistinguishable from nearfield and coastal stations. Even the highest measured concentrations of both indicators have been well below the standards. Overall results have demonstrated that water quality is sufficiently protected by treatment and disinfection at DITP. 57 Figure 6-5. Enterococcus , 1999–2014, compared to the contact recreation standard of a geometric mean not exceeding 35 organisms/100 ml. Figure 6-6. Fecal coliform bacteria, 1999–2014, compared to the shellfishing standard of a geometric mean not exceeding 14 organisms/100 ml. 58 Winter Flounder Sex Ratios Throughout the duration of the monitoring program, winter flounder catches have been dominated by females. In most years, females have made up most of the catch at every sampling site, and in some years and sites, the samples have been almost 100% female (Figure 6-7). Figure 6-7. Proportion of catch made up of female flounder, 1991–2015. DIF=Deer Island Flats, ECCB=eastern Cape Cod Bay, NB=Nantasket Beach, OS=outfall site In 2015, MWRA analyzed existing data from the monitoring program to determine whether there were detectable spatial or temporal trends (Moore et al. 2016). MWRA data were then compared with data from regional fisheries management agencies and other studies of winter flounder populations in New England and New Jersey. The analysis of monitoring-program data found that overall, 83% of MWRA’s total catch of winter flounder has been female. Regression analyses showed that catches were less skewed in the earlier years of monitoring, with the shifts towards greater percentages of females occurring during the 1990s. However, there was no consistent pattern in temporal shifts across sampling sites. For flounder caught near the outfall, the temporal shift has been slight, averaging 86% female in the early years of the monitoring program and 89% in more recent years, with a gradual increase in percent females during the 1990s and a gradual decline since 2000 (Figure 6-8). Fish caught in eastern Cape Cod Bay, the sampling site farthest from influence of MWRA’s past discharges or current outfall have had the highest percentage of females and no discernable trend in the years since the Massachusetts Bay outfall began to discharge. Female Flounder (%) 30 40 50 60 70 80 90 100 110 Outfall Startup 1991 1993 1995 1997 1999 2001 2003 2005 2007 2009 2011 2013 2015 DIF ECCB NB OS Outfall startup 59 Figure 6-8. Percent female flounder taken from the vicinity of the outfall site, 1991–2015. The red line denotes the trends detected in time-series analysis. The regional analyses compared MWRA data to information from coastal Maine and New Hampshire, Massachusetts, Rhode Island, Connecticut, and New Jersey and offshore on Georges Bank. None of the programs were specifically designed for analysis of sex ratios. Most of them targeted flounder with a greater size range than the larger, older fish targeted by MWRA to best examine the effects of longer exposure to chemical contaminants necessary for development of liver disease. The varying goals of the studies presented challenges in analyzing the results, as in general for winter flounder, percentage of females increases with length, particularly in the size range targeted by MWRA, longer than 30 cm total length. The comparisons confirmed that among the coastal populations, percent females increased with length between 30 and 40 cm (Figure 6-9), with about 83% total average percent females, the same as found by MWRA. Flounder from the offshore Georges Bank population did not show a skewed sex ratio. 60 Figure 6-9. Sex ratios compared to total length of winter flounder in MWRA surveys, other northeast coastal surveys, and on offshore Georges Bank. Percent females increased with total length in all coastal surveys. Black = Rhode Island, Gold = Maine–New Hampshire, Blue = Connecticut, Green = MWRA, Red = Massachusetts, Purple = New Jersey, Gray = Georges Bank Scientists have shown that sex ratios in fish may be linked to environmental factors, including temperature variations or exposure to chemicals that mimic endogenous hormones. However, the comparison of MWRA data with other data sets did not suggest any effect of temperature regimes or contaminant releases. The lack of female bias in the Georges Bank study is notable. However, temperature and contaminant inputs vary widely across the area included in the coastal studies. The consistently female-dominated collections of flounder in the size range targeted by MWRA, coupled with the lack of consistent temporal and spatial trends within the MWRA data set, suggests that there is no effect of the Massachusetts Bay outfall. Cape Cod Bay Studies The Center for Coastal Studies has conducted a monitoring program in Cape Cod Bay for many years, and since 2011, MWRA has collaborated on a portion of the program. The Center for Coastal Studies monitoring program includes MWRA water-column Station F29, on the southern boundary of Stellwagen Bank National Marine Sanctuary, MWRA Stations F01 and F02 in Cape Cod Bay and eight additional stations (Figure 6-10). 61 Figure 6-10. The Center for Coastal Studies monitors its own eight stations and three MWRA stations (F01, F02, and F29) in and near Cape Cod Bay. (Figure from the Center for Coastal Studies) The Center for Coastal Studies also monitors North Atlantic right whales, with aerial surveys flown along a series of east-west tracks over Cape Cod Bay. The surveys record presence, dive times, and whale behaviors. Right whales typically occur in Cape Cod Bay during January through May, entering when nutrient and chlorophyll levels are high, and their large zooplankton food is abundant. Total annual whale sightings had been high in recent years, compared to the late 1990s and early 2000s (Figure 6-11). Sightings during 2015, however, were lower than in most recent years. The whales entered Cape Cod Bay later than usual and remained about two weeks longer than usual, so that high numbers remained until almost the very end of the season. In May, whales congregated in the western part of Cape Cod Bay, where they were visible from the shore (Figure 6-12). There were 135 identified whales observed throughout the season, approximately one quarter of the known North Atlantic right whale population. While the number of identified right whales was much less than had been observed in 2007–2014, it was greater than the numbers observed in 1998–2006. The North Atlantic right whale remains protected under the U.S. Endangered Species and Marine Mammal Protection acts, with Massachusetts and Cape Cod bays considered to be key habitat for the western North Atlantic population. 62 Figure 6-11. Right whale sightings in Cape Cod Bay, 1998–2015. (Figure from the Center for Coastal Studies.) Figure 6-12. Whale sightings in Cape Cod Bay in May 2015. (Figure from the Center for Coastal Studies.) 63 References Codiga DL, Rex AC, Coughlin K. 2016. Ambient water quality monitoring of the Massachusetts Water Resources Authority effluent outfall: indicator bacteria in Massachusetts Bay 1999–2014. Boston: Massachusetts Water Resources Authority. Report 2016-01. 20 p. Latimer JS, Rego SA. 2010. Empirical relationship between eelgrass extent and predicted watershed-derived nitrogen loading for shallow New England estuaries. Estuarine, Coastal, and Shelf Science 90:231–240. Libby PS, Borkman DG, Geyer WR, Turner JT, Taylor DI, Costa AS. 2016. 2015 water column monitoring results. Boston: Massachusetts Water Resources Authority. Report 2016-12. 45 p. MWRA. 2001. Massachusetts Water Resources Authority Contingency Plan revision 1. Boston: Massachusetts Water Resources Authority. Report 2001-ms-071. 47 p. MWRA. 2010. Ambient monitoring plan for the Massachusetts Water Resources Authority effluent outfall Revision 2, July 2010. Boston: Massachusetts Water Resources Authority. Report 2010-04. 107 p. Moore MJ, McElroy A, Geoghegan P, Siskey M, Pembroke AE. 2016. Flounder monitoring report: 2015 results. Boston: Massachusetts Water Resources Authority. Report 2016-05. 40 p. Nestler EC, Diaz RJ, Hecker B, Pembroke AE, Keay KE. 2016. Outfall benthic monitoring report: 2015 results. Boston: Massachusetts Water Resources Authority. Report 2016-09. 33 p. Puente A, Diaz RJ. 2015. Response of benthos to ocean outfall discharges: does a general pattern exist? Marine Pollution Bulletin 101:174–181. Smolow M. 2016. Technical survey of nitrogen removal alternatives for the Deer Island Treatment Plant. Boston: Massachusetts Water Resources Authority. Report 2016-02. 37 p. Taylor DI. 2016. Boston Harbor water quality 1994–2015. Boston: Massachusetts Water Resources Authority. Report 2016-08. 14 p. Werme C, Rex AC, Hunt, C. 2012. Outfall monitoring overview background: 2012 update. Boston: Massachusetts Water Resources Authority. Report 2012-02. 59 p. 64 List of Acronyms cBOD Carbonaceous biochemical oxygen demand CHV Centrotubular hydropic vacuolation CSO Combined sewer overflow DDT Dichlorodiphenyltrichloroethane DIF Deer Island Flats DIN Dissolved inorganic nitrogen DITP Deer Island Treatment Plant DO Dissolved oxygen ECCB Eastern Cape Cod Bay EPA U.S. Environmental Protection Agency FF Farfield HMW High molecular weight IAAC Inter-Agency Advisory Committee IPUE Individuals per unit effort LC50 50% mortality concentration LMW Low molecular weight MassDEP Massachusetts Department of Environmental Protection MODIS Moderate Resolution Imaging Spectroradiometer MWRA Massachusetts Water Resources Authority NA Not analyzed/not applicable NACWA National Association of Clean Water Agencies NB Nantasket Beach NERACOOS Northeastern Regional Association of Coastal Ocean Observing Systems NF Nearfield NDBC National Data Buoy Center NOEC No observed effects concentration NPDES National Pollutant Discharge Elimination System OMSAP Outfall Monitoring Science Advisory Panel OS Outfall site PAH Polycyclic aromatic hydrocarbon PCB Polychlorinated biphenyl PIAC Public Interest Advisory Committee PSP Paralytic shellfish poisoning RPD Redox potential discontinuity SPI Sediment-profile imaging Massachusetts Water Resources Authority Charlestown Navy Yard 100 First Avenue Boston, MA 02129 (617) 242-6000
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