NPDES Permits in New England

Outfall Monitoring Science Advisory Panel Technical Workshop

Major Milestones of the Boston Harbor Project
Andrea Rex
Massachusetts Water Resources Authority, Boston MA

Brief re-cap of the major milestones of the Boston Harbor Project.

Effluent Quality
Steve Rhode
Massachusetts Water Resources Authority, Boston MA

This presentation will review historical trends in DITP effluent quality from the opening of the new treatment plant in 1995 to date. Historical data for annual metals and solids loadings, coliform levels and effluent concentration data for TSS, BOD and total PCBs will be presented. The correlation between the plant performance and effluent PCB loadings will be described. The composition of the detected PCBs and evidence for possible seasonal effects on effluent PCB concentrations will be discussed.

MWRA efforts to control PCB loading through the TRAC program will be reviewed, and the limitations of approved EPA testing methods relative to this effort will be described. Method issues associated with the total PCB monitoring requirement in the NPDES permit will be described and preliminary performance data for MWRA's proposed method will be presented.

Changes in Harbor Water Quality in Response to Transfer of Nut Island Flows
David Taylor
Massachusetts Water Resources Authority, Boston MA

In July 1998, flows of wastewater from Nut Island WWTF were transferred through Deer Island WWTF. The transfer ended more than four decades of wastewater discharges from Nut Island WWTF to the South Harbor, and increased flows from Deer Island WWTF to the North Harbor by one half. Analysis of long-term water quality data collected in the Harbor indicates that significant changes in water quality have occurred in the Harbor since transfer. The changes in the North Harbor and South Harbor have been quite different, and not necessarily the opposite of each other.

Comparison of average secchi depths before and after transfer indicates an increase in water clarity in the South Harbor, with no measurable decrease in water clarity in the North Harbor. In the South Harbor, the increase was greatest at the previous sites of the Nut Island outfalls, where average secchi depths increased 1 m, from 2 to 3 m's. Further afield in the South Harbor, the increase has been confined to winter, when average secchi depths have also increased 1 m from 3 to 4 m's. No decrease in clarity was observed at the Deer Island outfalls in the North Harbor, presumably because of the improved secondary treatment of wastewater at the Deer Island facility.

Unlike for water clarity, where changes have been confined to the South Harbor, concentrations of dissolved inorganic nutrients in both regions have shown changes. Twelve-month average concentrations of dissolved inorganic nitrogen (DIN) and phosphorus (DIP) have decreased in the South Harbor, and increased in the North Harbor, especially at the previous or current outfall sites. At the previous Nut Island outfalls, concentrations of DIN have decreased from 61 to 8 umol L-1. By comparison, concentrations at the Deer Island outfalls have increased from 55 to 72 umol L-1. Further afield in the South Harbor, concentrations decreased from between 10 or 11 umol L-1 to 6 or 7 umol L-1. In the North Harbor, the increases were in the same order as the decreases in the South Harbor, and from 9 to 12 umol L-1.

The effects of the transfer on phytoplankton biomass (measured as concentrations of chlorophyll a) have been complex. In the South Harbor, the responses differed among stations. At the Inner Quincy Bay station, average summer concentrations of chlorophyll decreased from 10 to 7 ug L-1, presumably in response to the decreased DIN loadings from Nut Island WWTF. At the outer Nantasket Roads station, the concentrations increased from 4 to 7.5 ug L-1, presumably in response to the increase in clarity that occurred at this station. In the North Harbor, no significant change in concentrations of chlorophyll could be detected, presumably because of light limitation of phytoplankton growth in this region.

Why the outfall?
Andrea Rex
Massachusetts Water Resources Authority, Boston MA

The outfall is the second of three important components in the protection of the Massachusetts Bay/Boston Harbor ecosystem. (1) cleaner effluent through source reduction and secondary treatment, (2) better dilution, and (3) constant monitoring and contingency planning. Because of the obvious improvements in Boston Harbor, some are questioning the need to use the new outfall/diffuser system. Others wonder if the outfall is not just transferring pollution from the Harbor "away." The outfall location was chosen after a four-year long process including oceanographic and engineering studies, regulatory review, and extensive public participation. The location and structure of the diffuser is designed to maximize dilution and mixing, which will minimize the effects of the major wastewater components, nutrients, remaining in secondary effluent. The greater dilution available also minimizes any risks in the unlikely event of treatment plant upsets. Modeling studies show that the outfall not only decreases the concentration of effluent in the Harbor, but also greatly reduces areas of lowest dilution along the coastline and into Massachusetts Bay. The outfall is designed to trap effluent below the pycnocline in the warmer months, so that nutrients will not be as available to promote surface algal blooms as at present. The length of the outfall affords a long contact time with chlorine disinfectant, which will enable MWRA to effectively disinfect the effluent with a minimum amount of chlorine, significantly less than is used at present. Finally, the outfall is necessary to achieve the maximum hydraulic flow through the treatment plant; and is an essential component in reducing combined sewer overflows.

Monitoring Plan
Mike Mickelson and Ken Keay
Massachusetts Water Resources Authority, Boston MA

As an important part of the Boston Harbor Project, the outfall for treated sewage effluent will soon be relocated from the Harbor to 9.5 miles offshore in Massachusetts Bay. Scientific evidence indicates that relocation will improve the Harbor without harming the Bay. Nevertheless, concerns about potential impacts have been raised. Over the last 8 years, MWRA has developed and implemented a comprehensive outfall monitoring program. Development of the program was guided by the Outfall Monitoring Task Force, which was succeeded by the Outfall Monitoring Science Advisory Panel.

The monitoring program incorporated the newest federal guidelines and received wide technical and public review. It focuses on important ecosystem components likely to be useful as indicators of outfall effects, and consists of four project areas: effluent, fish and shellfish, water column, and benthos.

The monitoring began in 1992 to provide a baseline for comparison to conditions after the outfall is relocated. The 8-year baseline has increased our understanding of the system, allowing MWRA and the oversight committee to translate the stated concerns about the Bay outfall into a set of thresholds which express expectations for the quality of the Bay. Two additional components render the thresholds an effective management tool: a commitment to rapid notification of threshold exceedances, and an up-front consideration of possible responses to those exceedances.

The monitoring program has been incorporated into the new discharge permit for the Bay outfall, ensuring MWRA's commitment to comprehensive monitoring with expert oversight, rapid reporting of monitoring results including threshold exceedances, and responsiveness to concerns.

MONITORING RESULTS

The Physical Environment:
Circulation and Water Properties in Massachusetts Bay
Rocky Geyer
Woods Hole Oceanographic Institution, Woods Hole, MA

Massachusetts Bay is part of the larger circulation regime of the Gulf of Maine. As such, its currents, water properties, and biology are strongly influenced by the conditions in the Gulf of Maine. This interconnection applies to the outfall site as well as Mass Bay as a whole. The dominant characteristic of the water properties of Massachusetts Bay is the large seasonal variation in stratification, from well-mixed conditions in the winter to strong stratification in the summer. There are interannual variations in bottom water temperature and dissolved oxygen at the outfall site that appear to be related to wind forcing. Persistent southerly winds during the summer lead to colder bottom temperatures and higher DO. Weaker southerly winds lead to warmer bottom waters and lower DO. The USGS circulation model indicates that the main influence of the new outfall will be a reduction of the impacts of the effluent in Boston Harbor. The far-field will not be significantly altered.

Water Quality Monitoring Program and Baseline Results
Carlton Hunt and Scott Libby
Battelle, Duxbury, MA

The Massachusetts Water Resources Authority (MWRA) has collected water quality data in Massachusetts and Cape Cod Bays for the Harbor and Outfall Monitoring (HOM) Program since 1992. This monitoring is in support of the HOM assessment of the environmental responses that may result from the relocation of effluent discharge from Boston Harbor to Massachusetts Bay. The data are being collected to establish baseline water quality conditions and ultimately to provide the means to detect significant departure from that baseline. The surveys have been designed to evaluate water quality on both a high-frequency basis for a limited area in the vicinity of the outfall site (nearfield surveys) and a low-frequency basis over an extended area throughout Boston Harbor, Massachusetts Bay, and Cape Cod Bay (farfield). The water column monitoring includes parameters that respond to nutrient loading as well as measurement of anthropogenic viruses, fecal coliform bacterial, and other potential water borne measures of system response such as paralytic shellfish poisoning (PSP). This presentation considers the baseline nutrient related monitoring results.

The water quality monitoring program includes continuous vertical profiles of in situ temperature, salinity, dissolved oxygen, chlorophyll fluorescence, beam attenuation (particle fields), and irradiance, from the water surface to within 5 m of the bottom at each station. Discrete samples from 3 or 5 depths (depending on water column depth) are collected for nutrient analyses (all forms), total suspended solids, chlorophyll a, and dissolved oxygen. Samples are also collected for phytoplankton and zooplankton species enumeration at representative stations throughout the Massachusetts Bay.

Eight years of baseline data show that there is substantial variability throughout the system, both with depth in the water column as well as gradients extending seaward from Boston Harbor. The exchange of Boston Harbor waters, which contain high nutrient levels, with nearfield and coastal waters produces a plume of Harbor water that extends into the western nearfield area and southward along the coast of western Massachusetts Bay. This feature is persistent throughout the year and across all years. These horizontal gradients extending from Massachusetts Bay are less distinct in the bottom waters, partially as a result of water column stratification that occurs from the late spring through the late fall. MWRA's effluent discharge at the mouth of Boston Harbor provides a localized source of nutrients which feeds this coastal plume.

The seasonal nutrient cycle in the Bay is well described and follows conventional wisdom regarding nutrient uptake and control of primary production, phytoplankton and zooplankton species composition, chlorophyll biomass, and dissolved oxygen cycle. Chlorophyll, a measure of the phytoplankton biomass, is one of the water quality measurements and a key indicator in the water quality-monitoring program. Temporal and regional concentrations are variable within the system. Primary producers undergo nutrient limitation in the surface waters in the summer and light limitation in the winter. This results in a seasonal chlorophyll cycle that progresses through a winter spring bloom dominated by diatoms through a period of lower concentration in the summer that is dominated by microflagellates. Maximum chlorophyll levels are generally found in the pycnocline during the stratified period, although the Harbor plume influences distribution in the western parts of the Bay. Chlorophyll levels then progress through a fall bloom, often related to overturn of the stratified water column. This bloom is often dominated by diatoms. During any given season, near monospecific blooms of diatoms or other species such as Phaeocystis can bloom to high levels. The latter species can cause undesirable ecological affects. Of note in the system is a consistent fall bloom that is often larger and more sustained than the classical winter-spring bloom in temperate coastal systems. The largest sustained bloom of the baseline period occurred from the late winter of 1998 through late April of 1999.

Bottom water dissolved oxygen, another key indicator of ecosystem health, also follows a well-defined seasonal cycle. In winter the water column is well mixed and the DO is saturated with respect to atmospheric conditions. As stratification sets up, the DO levels in the bottom waters begin to decline. The rate of decline is relatively constant among years. The DO concentrations at the on-set of stratification, the amount of carbon deposited in the sediments during the fall and winter, and the bottom water temperatures reached in the late fall, all affect the bottom concentrations reached prior to water column turnover. During October 1994 during the baseline period, the mean nearfield bottom water DO decreased to less than 6.5 mg/L (the caution level established under MWRA monitoring program). The DO caution level was approached in early September 1999, possibly in response to the large winter bloom in 1999, and the extended drought and high air temperature experienced since mid-1998.

Phytoplankton and zooplankton community composition generally is consistent within the system and across seasons. Subregions of Massachusetts Bay have similar species composition, although the timing of bloom events may differ. Total numerical abundance varies greatly among samples, surveys, seasons, and regions. Although the variability within surveys is high, distinct temporal patterns are evident in the data. Numerically, diatoms and microflagellates are the major plankton groups within the phytoplankton community. Carbon based abundance is dominated by diatoms. Alexandrium tamarense bloom events have not occurred since 1993. The zooplankton community in Massachusetts Bay is similar to that of the Gulf of Maine and Buzzards although abundance varies among samples, survey, season, and regions.

Because the new outfall relocates the current discharge and discharges at a depth below the photic zone, the effluent will be more diluted than currently achieved, and surface production of phytoplankton biomass is expected to be less than under the current discharge. Thus, the net ecological results are likely to be small and limited to the nearfield. In addition, nutrient fields in the outer Harbor are expected to decrease in concentration and extent, as will the surface chlorophyll levels. Nutrient fields in Massachusetts Bay are not expected to change appreciably in the vicinity of the outfall, although am slight increase in ammonium concentrations against the lower offshore background level may be observed. The coastal plume is also expected to be less distinct and less intense and chlorophyll levels will decrease in surface waters of the western nearfield. Moreover, bottom water DO values in the Bays are not expected to changes substantially relative to the current baseline history.

Changes in the phytoplankton and zooplankton species abundance and composition are not expected to change in the Bays as a result of the transfer of effluent from the Harbor mouth into Massachusetts Bay.

Utility of the Bays Eutrophication Model (BEM)
in the Harbor Outfall Monitoring (HOM) Program
James Fitzpatrick and Richard Isleib, P.E.
HydroQual, Inc., Mahwah, NJ

A coupled hydrodynamic/water quality model has been developed for the Massachusetts Bays system. This model known as the Bays Eutrophication Model (BEM) was developed for the Massachusetts Water Resources Authority (MWRA) to help understand the relationship between circulation, nutrients, and primary productivity in the Massachusetts Bays system. The model was also developed to provide MWRA and other water quality managers with a tool for projecting water quality in Massachusetts and Cape Cod Bays in response to various nutrient management alternatives. The BEM can also be used to assist in the development of additional water quality monitoring needs and field and laboratory research efforts.

The BEM has been recently applied to a three-year HOM data set collected between 1992 and 1994. The data set contains a number of interesting water quality features, including a bloom of the diatom species Asterionellopsis glacialis in the fall of 1993 and very low dissolved oxygen concentrations in the fall of 1994. This presentation will focus on the ability of the model to reproduce these water quality data features, as well as to explore some model limitations.

The presentation will also provide an overview of the utility of the model in developing a system-wide nutrient budget and in assisting in the evaluation of the spatial and temporal distribution of various nutrient inputs within the Massachusetts Bays system.

Predicting the fate of sediments and associated contaminants in Massachusetts Coastal Waters
Bradford Butman, Michael H. Bothner, Harley J. Knebel, Frank Manheim, Marilyn Buchholtz ten Brink, and Richard P. Signell
U.S. Geological Survey, Woods Hole Field Center, Woods Hole, MA

Many contaminants introduced to the coastal ocean are associated with particles. After repeated cycles of transport, deposition, resuspension, and biological and chemical interactions, contaminants on particles eventually may be buried in bottom sediments. The U.S. Geological Survey and the Massachusetts Water Resources Authority are collaborating in a 12-year study designed to provide an understanding of how sediments and associated contaminants are transported and where they accumulate in the Massachusetts Bays system. The overall objective is to provide a predictive capability and understanding of the fate of contaminants associated with fine-grained sediments. The multi-disciplinary project has focused on four questions of interest to scientists and to managers at MWRA and other regulatory agencies.

1. What are the best locations for monitoring changes in sediment contaminants on a regional basis? Sea-floor mapping, utilizing side scan sonar, high-resolution seismic reflection profiling, multibeam bathymetry, sampling, video and bottom photography, has shown that the sediment texture and other bottom features in Massachusetts Bay are patchy and that major changes occur over a wide variety of spatial scales. The variability is due to the irregular bottom topography, past and present sources of sediment, and the processes causing transport. Maps show the location and extent of erosional and depositional environments and provide a regional context for the interpretation of bottom samples and benthic observations. Fine-grained sediments typically indicate areas of sediment accumulation; coarse-grained sediments or boulders define areas where sediments are scoured and winnowed by currents. Regional maps of sedimentary environments have provided a framework for designing a cost-effective monitoring program and for selection of the new outfall site. The USGS, in cooperation with the MWRA, has established sediment monitoring stations at two depositional sites in the vicinity of the new ocean outfall. These stations are part of the 20 near field stations that MWRA samples annually. Samples have been taken at these USGS sites three times each year since 1989 to document seasonal and inter-annual variability in contaminant concentrations, and to provide a baseline against which to measure future change. In addition, samples have been obtained at representative stations in Massachusetts and Cape Cod Bay in 1992 and 1998. In general, concentrations of metals in the surface sediments decrease with distance from Boston Harbor and are below the ERM guidelines of Long and others (1995).

2. How are nutrients, sediments, contaminants, and other water-borne material transported regionally in Massachusetts and Cape Cod Bays, and locally around the new and old outfalls? Hydrodynamic modeling of the ocean circulation provides a framework for understanding the regional flow and mixing, and the basis for simulations of water quality. With the existing outfall locations, high effluent concentrations are found within Boston Harbor and along the coastline immediately south. With the new outfall location, high concentrations of effluent are found only within a few kilometers of the outfall, concentrations are dramatically lower in Boston Harbor, and concentrations in most of Massachusetts Bay (including the region near Stellwagen Bank) are not significantly changed from their existing low levels. At the new outfall location in summer, effluent is trapped at mid-depth beneath the warm surface layer, while effluent from the existing outfalls remains near the surface. Because nutrients from the new outfall are trapped in waters that are already nutrient rich and where phytoplankton growth is light-limited, the impact of sewage-borne nutrients is decreased. Computer simulations also indicate that water-quality standards could be met with a secondary treatment capacity 25% smaller than originally planned. This design change saved taxpayers approximately $160 million in construction costs.

   While the effluent concentration simulations show that greater dilution at the new outfall site can decrease the impact of pollutants effects in the water column, contaminants that settle to the bottom can accumulate in the sediments over the long-term. For this reason, the implementation of secondary treatment will greatly reduce the levels of particles and contaminants entering the system.

   Boston Harbor, Stellwagen Basin and Cape Cod Bay are the long-term sinks for fine-grained sediments. The transport and accumulation of sediments in the Massachusetts Bays is determined principally by the residual circulation, major storms, the bathymetry, and the geometry of the semi-enclosed basin. The mean current, driven principally by the along-shore coastal current in the western Gulf of Maine, proceeds in a counterclockwise direction around Massachusetts Bay. Superimposed on this residual flow pattern are tidal, density, and wind-driven currents that can alter the direction and speed of residual flow on a daily basis. Northeast storms generate large swell that propagate into Massachusetts Bay from the Gulf of Maine. The oscillatory currents associated with these waves cause resuspension of bottom sediments in water depths less than about 50 m over areas exposed to the northeast, principally along the western shore of Massachusetts Bay. The near-bottom currents associated with the northeast winds are to the south and offshore and carry the resuspended material southward toward Cape Cod Bay and offshore into Stellwagen Basin. Most of Cape Cod is sheltered from the large swell associated with northeasters, and in deep Stellwagen Basin, the waves are rarely large enough to resuspend the sediments. Sediments that are transported to these two areas from the western side of Massachusetts Bay, by the residual circulation or the storm-driven currents, are less likely to be resuspended again, and thus these areas are long-term sinks for fine sediments and associated contaminants. This conceptual model is supported by direct observations of currents and sediment resuspension during storms, wave and 3D current modeling, by the observed accumulation of fine grained sediments in Cape Cod Bay and Stellwagen Basin, and by the lack of fine sediment along the western shore of Massachusetts Bay. The model is also consistent with the distribution of silver and Clostridium perfringens spores, most likely input to the Massachusetts Bays from Boston's sewage system. Recent observations of internal waves in Stellwagen Basin in the summer suggest that these waves may also play a role in the transport of sediments from the nearshore into the deeper basins.

3. What are the concentrations of pollutants in sediments of western Massachusetts Bay and how have they changed with time? Geochemical determinations indicate that metal concentrations in bottom sediments near the future outfall are presently below the ERM toxicity guidelines of Long and others (1995). The time-series observations at a monitoring site near the new outfall showed a more than 2-fold increase in the concentrations of silver following a major storm in December of 1992. Similar changes were measured in other variables such as Clostridium perfringens spore counts, inventories of natural radioisotopes, and sediment texture. These changes are evidence for storm-induced resuspension and transport of fine sediments and associated contaminants from shallower inshore areas to deeper depositional areas offshore. The characterization of natural variability, particularly related to high energy events such as storms, provides a critical framework for understanding the cause of future changes.

4. What is the distribution of contaminants in harbor sediments, and are the concentrations decreasing with time in response to MWRA's harbor cleanup program? Establishment of a contaminated-sediment data base that includes contaminant information from a wide variety of sources, and continuing geochemical observations have revealed areas of the harbor, particularly the inner harbor, where some metal concentrations are above toxicity guidelines. However, a time-series of collection and analysis of surface sediments at monitoring locations indicates that concentrations of lead and other metals in the surficial sediments have decreased by about 50% over the last 20 years. Boston Harbor is getting cleaner.

   Geologic mapping, physical oceanography, biology, geochemistry, and hydrodynamic modeling have all contributed to developing an understanding of the transport and fate of sediments in the Massachusetts Bay system. The research has been enhanced by cooperation among research partners from the academic community and from state and federal agencies. In addition, the project benefited from a continuing, long-term commitment by all partners, a multi-disciplinary approach, a regional system-wide perspective, stable long-term funding, and interactions between management and science. The project provides a framework for assessing the effects of the new ocean outfall on Massachusetts coastal waters and is a model for studies of similar systems elsewhere.

   Massachusetts Bay is a complex coastal oceanographic system affected by both natural processes and past and present anthropogenic activities. The Bay is partially separated from the Gulf of Maine by Stellwagen Bank, which rises to about 30 m of the sea surface. The seafloor environment in the Bay varies from mud in the depositional basins to coarse sand, gravel, and bedrock on the topographic highs. The region immediately surrounding the outfall site consists of a series of ridges and valleys.

   Boston Harbor, Stellwagen Basin, and Cape Cod Bay are areas of sediment accumulation. In general, fine sediments do not accumulate in the region surrounding the outfall, except in a few isolated locations. Sediments and associated contaminants are transported to the south and offshore by the mean flow and storms in the Gulf of Maine. A baseline has been established for contaminants in depositional sites. Inventories of silver show that Boston Harbor, Stellwagen Basin, and Cape Cod Bay are long-term sinks for contaminants. Concentrations of lead and other heavy metals in the surficial sediments of Boston Harbor have decreased by about 50% between 1997 and 1994.

Soft-bottom Benthic Community Monitoring in the Boston Harbor- Massachusetts Bays System
Kenneth E. Keay
Massachusetts Water Resources Authority, Boston, MA
Roy K. Kropp
Battelle, Duxbury, MA
Eugene D. Gallagher
University of Massachusetts, Boston, MA
Robert J. Diaz
R. J. Diaz and Daughters, Ware Neck, VA

Soft-bottom benthic monitoring carried out by MWRA in the past decade in the Boston Harbor-Massachusetts Bay system constitutes the best long-term dataset available in this region for investigating the complex interactions of physical, ecological, and anthropogenic factors that influence these sensitive indicators of environmental health. This presentation summarizes some of the characteristic community types determined by the monitoring and briefly details the more important findings of the monitoring to date.

Boston Harbor: Studies from the late 1970s through the late 1980s found that many soft-sediment Harbor areas, especially in northern sections of Boston Harbor, contained assemblages dominated by pollution-indicating polychaete worms such as Capitella spp., Polydora cornuta, and Streblospio benedicti. Less impacted communities, dominated by the crustacean amphipod Ampelisca vadorum and other animals less indicative of polluted habitats were found in southern parts of the Harbor and sporadically in the North Harbor.

MWRA's long-term Harbor benthic monitoring began in September 1991, and early results were similar to those of historic studies. Following the December 1991 cessation of sludge discharge to the Harbor, (these changes were probably also influenced by the fall 1991 "Halloween" Nor'easter), diversity throughout Boston Harbor increased, and by the mid-1990s stabilized at a higher level than in the past. This was associated with a rapid increase in the distribution of Ampelisca and other amphipod-dominated communities throughout the harbor, from being present at fewer than 25% of the stations sampled in 1989-90 to >60% in the mid-1990s. Severely degraded communities are now found only at a very few stations where fine sediments rapidly accumulate, such as portions of the Inner Harbor or in Savin Hill Cove next to U/Mass Boston, which are near combined sewer overflows and other sources of wastewater

Massachusetts Bays: Soft-bottom benthic communities in the vicinity of the future outfall inhabit a spatially and temporally variable environment. Areas dominated by depositional fine sands and muds, in which organic carbon and/or contaminants might accumulate are distributed primarily to the west of the outfall. Sediments with a substantial proportion of fine sand and mud contain a polychaete dominated community characterized by moderate abundances of one or more of the polychaetes Spio limicola, Prionospio steenstrupi and Mediomastus californiensis though the relative abundance of these species changes from year to year. The few stations with primarily medium-coarse sand and gravel usually contain an assemblage dominated by amphipods such as Crassicorophium crassicorne and by sand-dwelling polychaetes like Polygordius sp. A. Major sediment transport events like those documented by USGS in winter 1992-93 have caused complete changes in sediment character in some areas (for example, one site changed from >80% mud in 1992 to 99% sand and gravel in 1993).

The nearfield fine sand/mud community is very similar to that found in two farfield reference areas, south of Gloucester and about 5 nautical miles southeast of the nearfield. Reference stations deeper than about 50 meters ranging from east of Cape Anne south through Stellwagen Basin have a relatively distinct community, which shares some species with the shallow-water sand/mud community but also has dominant species not found in other regions. Communities at two slightly shallower stations in Cape Cod Bay are normally more similar to each other than to other stations (however, this pattern did not hold in 1998 samples). These Cape Cod Bay stations show affinities to both the offshore assemblages and to the western Massachusetts Bay fine sand/mud communities.

Samples from the Bays routinely contain about twice as many different species as do Boston Harbor samples (they exhibit high species richness) and species evenness is much higher than in Harbor samples (in which 70%+ of the animals present are often from only 1-3 species).

Analyses of the long-term outfall monitoring benthic data document striking changes in diversity. The average number of species per grab in near-field samples decreased about 25% between 1992 and 1993, and then steadily increased each year until leveling off in 1997 and 1998; diversity was substantially higher than in 1992. A similar pattern is evident in the data from the rest of the Bays as well. The cause or causes of this change are currently unclear; possibilities include a region-wide response to sediment transport from 1992-1993 winter storms or to some other large-scale event.

Benthic Nutrient Cycling in Boston Harbor and Massachusetts Bay
Anne Giblin, Charles Hopkinson, and Jane Tucker
The Ecosystems Center, Marine Biological Laboratory, Woods Hole, MA, 02543

Monitoring of benthic respiration, benthic nutrient release, and denitrification was begun in 1992 at selected stations in Boston Harbor and Massachusetts Bay and is still continuing. The goal of the monitoring is to determine the role of the sediments in nutrient cycling and oxygen dynamics. Measurements have been made 2-5 times a year. Several new stations were added in the Harbor in 1995.

From 1992-1995, oxygen uptake rates from Harbor sediments were quite high and very variable. Interannual oxygen uptake rates continue to be variable at most Harbor stations, however, the extremely high rates observed in the early part of the study (1993-1995) have not been repeated. Highest oxygen uptake rates are usually associated with a dense cover of tube building amphipods. Although the amphipods continue to be present, the lower rates now observed near the Long Island sludge disposal site suggest some "mining" of sediments organic stores may have taken place.

Harbor sediments are also an active site of denitrification and more than half of the nitrogen mineralized in the sediments is subsequently denitrified and lost from the ecosystem. Although the proportion of nitrogen lost from the sediments is high, it is typical of marine sediments. However, because most of the nitrogen entering Boston Harbor is not cycled through the sediments, only a relatively minor percentage of the N inputs to Boston Harbor from sewage and other sources is lost by denitrification. Hence, moving the outfall should not have a large effect on the N budget of Massachusetts Bay as a whole.

Sediment fluxes were not measured in Massachusetts Bay during 1998. Previous measurements had shown that benthic respiration rates exhibited low interannual variability, less than 20%. This suggested there would be a high power to detect any change due to the outfall relocation. Benthic respiration rates measured in 1999 have been higher than average, and may reflect greater carbon loading to the sediments from an unusually large diatom bloom in early 1999, and warmer than usual bottom water temperatures. However, the October rates will be needed to determine if this year's rates would have fallen outside what was considered normal based upon the 1992-1997 data.

Nearfield Hard-bottom Communities Near the Massachusetts Bay Outfall
Barbara Hecker
Hecker Environmental Consulting, Falmouth, MA

Benthic communities inhabiting hard-bottom habitats (drumlins - rock covered topographic highs) near the Massachusetts Bay outfall have been surveyed annually since 1995. The surveys were conducted using a Benthos Mini Rover ROV to collect video images and color slides at selected sites (waypoints) near the outfall and at reference sites further away. The number of waypoints surveyed has expanded from 19 waypoints (17 near the outfall and 2 reference) in 1995 to 23 waypoints (16 near the outfall, 6 reference, and diffuser head #44) in 1997. Diffuser #44 will not discharge effluent, and was added to the survey because it affords a worst-case example in the extreme nearfield. The major emphasis of the hard-bottom survey was shifted from video images to color slides since 1996, because of the greater resolution afforded by still images. Approximately 20 minutes of video footage and 30 color slides were collected at each waypoint. The video images were used primarily to qualitatively evaluate sea floor characteristics (habitat relief, substratum size class, degree of sediment drape, and habitat heterogeneity) and the occurrence of sparse larger organisms. The still photographs were used to semi-quantitatively assess the relative proportion of benthic inhabitants at each waypoint.

The sea floor on the drumlin tops consisted typically of a mix of boulders and cobbles. Habitat relief in these areas varied from high (predominantly boulders) to moderate (cobbles with occasional boulders). Sediment drape on the drumlin tops was usually light to moderate, but was occasionally heavy at locations that supported a high abundance of upright algae. The sea floor on the flanks of the drumlins usually consisted of a cobble pavement interrupted by occasional patches of gravel, sand or boulders. Habitat relief in these areas usually ranged from low to moderate, depending on the number of boulders present. Sediment drape in the drumlin flank areas usually ranged from moderate to heavy. While some areas were homogeneous with regard to sea floor characteristics, many areas were quite heterogeneous, such that slight lateral shifts in position resulted in markedly different habitats. This spatial heterogeneity was frequently most pronounced on the flanks of the drumlins.

The benthic communities inhabiting the drumlins appeared to be controlled by a combination of location on the drumlin (concurrent with depth), substratum size class and associated habitat relief, and degree of sediment drape. Algae usually dominated the benthic communities inhabiting the tops of drumlins, while invertebrates (mostly encrusting or attached forms) frequently dominated the communities on the flanks. The encrusting coralline alga Lithothamnion spp. dominated in drumlin top areas that had little sediment drape. In contrast, upright algae (Asparagopsis hamifera, dulse and shot-gun kelp) dominated in areas of high relief. The holdfasts of the upright algae appeared to trap sediment, resulting in a reduction of Lithothamnion. Other taxa commonly encountered were the horse mussel Modiolus modiolus, the northern sea star Asterias spp., the sea pork tunnicate Aplidium spp., and the cunner Tautogolabrus adspersus. Sediment areas tended to be depauperate, while the diffuser heads typically supported dense aggregations of the frilly anemone Metridium senile and numerous Asterias spp.

The benthic communities were temporally quite stable over the 1995 to 1998 time period. Within-site changes in the percent cover of Lithothamnion spp. and in-community composition between sampling periods frequently reflected slight lateral shifts in sampling location. This temporal stability enhances the likelihood of detecting large changes in the composition of the hard-bottom communities during discharge monitoring. Of all species encountered during this study, Lithothamnion spp. was the least variable and most predictable. As a result, Lithothamnion appears to hold the most promise as an "indicator" of habitat health during monitoring of the outfall discharge. It is abundant, widely distributed, predictable in terms of habitat requirements, and appears to be sensitive to particulate loading.

Caged Mussel Bioaccumulation Monitoring in Massachusetts and Cape Cod Bays
Lisa Lefkovitz and Carlton Hunt
Battelle, Duxbury, MA
Maury Hall
Massachusetts Water Resources Authority, Boston, MA

Caged mussels have been deployed since 1991 as part of the NPDES permit requirement to address bioaccumulatable contaminants and human health exposure associated with the Massachusetts Bay Outfall. This assessment is conducted by deployment of caged blue mussels near the effluent discharge location and at reference areas. Mussels were collected at two locations: Gloucester and Sandwich, for deployment at a number of locations in Boston Harbor and Massachusetts Bay. Mussel composites from each deployment location, as well as pre-deployment mussels, were analyzed for selected organics and metals. To date, chemical concentrations for both organics, such as PCBs and chlorinated pesticides, and mercury, have been highest in caged mussels deployed at Boston Inner Harbor (BIH) and lowest at the Outfall site. A new location in Cape Cod Bay, added in 1998, shows even lower concentrations than the Outfall location. Concentrations measured in 1998 were among the lowest observed since 1991, especially at BIH and Deer Island (DI). Lead and mercury concentrations have been much more variable among the sites over time. Post discharge results will be compared to the baseline period to determine if discharge from the Outfall results in appreciable change to baseline values. Concentrations measured at the Massachusetts Bay Outfall site in 1998 were well below the MWRA Threshold levels, indicating no health risk.

Flounder Histology and Tissue Chemistry
Michael Moore
Biology Department, Woods Hole Oceanographic Institution, Woods Hole, MA

Contaminant-associated liver tumors and hydropic vacuolation were first described in winter flounder from near the Deer Island outfall in 1985. The prevalence of these lesions had decreased substantially by the early 90's. Today tumors are very uncommon. Hydropic vacuolation is now found in 30-40% of the adult fish examined. Since 1991, Deer Island and four other stations have been annually sampled as part of the harbor and outfall monitoring program. Comparable prevalences to Deer Island have been detected at the Broad Sound site, with lower levels at the Massachusetts Bay Outfall site and off Nantasket Beach. The lowest prevalence has been consistently observed in flounder from a station in Eastern Cape Cod Bay. A suite of organic and inorganic chemical contaminants have also been measured annually in liver and fillet samples. Comparable between-station trends have been seen for most of the organic compounds. Less obvious patterns have been discernible for inorganic compounds. A gradual decrease in chemical exposure and effect at each station is the most likely outcome after activation of the offshore outfall, as source reduction efforts continue.

POSTERS

Transport Of Toxic Alexandrium Populations into Massachusetts Bay
Donald M. Anderson and Bruce A. Keafer
Biology Department, Woods Hole Oceanographic Institution, Woods Hole, MA

Toxic or harmful algal blooms (commonly called "red tides") are a serious economic and public health problem throughout the US and the world. In the New England region, the most serious problem in this context is that of paralytic shellfish poisoning (PSP), a potentially fatal neurological disorder caused by human ingestion of shellfish that accumulate toxins as they feed on dinoflagellates of the genus Alexandrium. Past research on these phenomena has led to the hypothesis that toxic Alexandrium cells are introduced to the Massachusetts and Cape Cod Bays via a coastal current formed from the outflow of rivers in southern Maine. When this coastal current enters Massachusetts Bay, it sometimes passes over or close to the new MWRA outfall site. This leads to concern that nutrient inputs from the outfall might stimulate the growth of red tide algae, worsening the PSP problem. This issue is especially relevant to South Shore and Cape Cod communities "downstream" from the outfall, given the typical north-to-south mesoscale circulation of the Bays. Recent public controversy over these possible effects have highlighted how little is known about the PSP phenomenon within the Bay itself or about the manner in which the PSP toxins move through the food chain to zooplankton, fish, and marine mammals. The general objective of this poster is to provide an overview of our understanding of the dynamics of Alexandrium within Massachusetts Bay, focusing on field data during one year (1993) when cells were abundant within the Bay and one year (1994) when they were not. A general conceptual model of how blooms and toxicity develop within the bay will be presented and discussed in the context of the Massachusetts Bay outfall.

Sediment Contaminant Monitoring in Massachusetts and Cape Cod Bays
Deirdre Dahlen, Lisa Lefkovitz and Carlton Hunt
Battelle Duxbury Operations, Duxbury, Massachusetts

Monitoring of toxic contaminants in sediments is one of three main concerns addressed by the Benthic (Sea-Floor) Monitoring component of the MWRA Harbor and Outfall Monitoring (HOM) program. Benthic monitoring collects data on the benthic macrofauna and flora, and the physical properties and levels of organic matter, nutrients, sewage indicators, and contaminants in the sediments in which the macrofauna reside. Measurements are made over a wide geographic area influenced by many natural and anthropogenic factors including effluents from MWRA wastewater outfall. Outfall monitoring includes nearfield and farfield sampling but is focused most intensely on the nearfield area (<8 km from outfall) where changes in water and sediment quality following initiation of the discharge is most likely to be detected, if they occur. Farfield locations (>8 km from the outfall) serve primarily as reference areas for the nearfield or as monitoring stations if the discharge affects sites distant from the diffuser. In addition, a Special Contaminant Study is performed three times a year at stations NF08, NF22, NF24, and FF10 to address possible short-term transport and impact.

The objectives of sediment contaminant monitoring component of the HOM program are to

• Determine changes in the physical characteristics, organic matter content, chemical contaminant concentrations in sediments near the diffuser;
• Collect physiochemical data to understand interrelations among these parameters and the benthic communities;
• Establish baselines in Massachusetts and Cape Cod Bays;
• Detect change in system after discharge; and
• Evaluate contaminant levels against the monitoring thresholds

Concentrations of organic and metal contaminants are generally low and highly variable. Variability is related to grain size and TOC, which are variable also. Nearfield average concentrations of organic and metal contaminants are well below levels of ecological concern and are similar over time.

Long-term Trends in Productivity
Aimee Keller, Candace Oviatt , Tarquin Dorrington, Gywnne Holcombe, and Laura Reed
Graduate School of Oceanography, University of Rhode Island, Narragansett, RI

Primary productivity represents the autotrophic fixation of carbon dioxide by phytoplankton during photosynthesis. Since phytoplankton form the base of the marine food web, primary production is the key process that brings food into a marine system. Changes in the rate of primary production are essential to measure since they affect not only the concentration of plant biomass but also the organisms that eat them. Phytoplankton productivity is also important since it is closely tied to the cycling of nutrients and the concentration of oxygen. The major goal during the baseline monitoring of productivity was to establish the range and variability in annual productivity at two sites: near the site of the Massachusetts Bay outfall (Stations N04, N16 or N18) and near the entrance of Boston Harbor (Station F23).

Annual productivity ranged from a low of 141 g C m-2 y-1 at station N04 to a high of 787 g C m-2 y-1 at Station F23 from 1992 -1998. Mean annual productivity was higher (mean 494 g C m-2 y-1) and more variable near the Harbor entrance (Station F23) than at the nearfield sites (Stations N04, N16 and N18). At station F23 productivity varied greater than 5-fold over the 7-year sampling period. Average annual productivity and variability around the means were considerably lower at Stations N04 (mean 285 g C m-2 y-1) and Station N16-18 (mean 396 g C m-2 y-1). Annual productivity in 1998 was unusually low at all three sites (<160 g C m-2 y-1) due to the failure of the winter-spring phytoplankton bloom. The absence of the 1998 bloom was linked to warmer winter temperature and increased grazing by zooplankton during the bloom period.

The seasonal cycle of areal primary productivity (mg C m-2 d-1) at the nearfield stations (N04, N16, N18) was generally characterized by a well-developed winter-spring bloom of several weeks duration, high production during the summer and a less prominent fall bloom. The majority of production (mg C m-2 d-1) typically occurred in the upper 20 m of the water column at the nearfield sites. At the Boston Harbor station (F23) a gradual pattern of increasing areal production from winter through summer was more typical with the majority of production occurring in the upper 5-10 m of the water column.

If nutrient concentrations increase in the euphotic zone as a result of the relocated outfall primary production may increase perhaps leading to greater phytoplankton biomass or increased secondary productivity.

Juvenile Lobsters at the New Outfall Site:
Comparisons With Inshore an Population and Discussion of Potential Outfall Impacts on Lobster Populations Kari L. Lavalli
Southwest Texas State University, San Marcos, TX
Roy K. Kropp
Battelle Duxbury Operations, Duxbury, MA
Kenneth E. Keay
MWRA, Boston, MA

In late May 1998, the Massachusetts Water Resources Authority (MWRA) was directed by the Outfall Monitoring Task Force to design and execute a study in the cobble-boulder habitats of the new outfall nearfield region to sample early benthic phase lobsters ("EBPs", 5 to 40 mm carapace length (CL)), particularly that of new recruits ("young-of-the-year", <12 mm CL) and yearling lobsters (shelter-restricted, <20 mm CL). Both of these life history phases are thought to be relatively nonmobile, obligate shelter-dwellers. MWRA was also required to determine if the numbers of these life history stages were comparable to those of nearby inshore habitats. This mandate resulted from serious concerns about the effects that the new outfall might have on juvenile lobsters and, thus, the future of the economically important lobster fishery.

MWRA responded to this mandate by proposing a survey plan that was developed from examination of videotapes from a remotely-operated vehicle survey conducted in September, 1994, and previous data on lobster density from hard bottom surveys to determine suitable locations for sampling. A mathematical calculation was used to determine an appropriate minimum sample size for the collection of species occurring only rarely in a region. These tactics were designed to maximize the chances of locating young-of-the-year and shelter-restricted lobsters at the outfall vicinity. In early September 1998, EBP-density sampling was undertaken by the foremost experts in airlifting for lobsters underwater at both the vicinity of the outfall and two nearby inshore stations. The data collected showed significantly lower densities of young-of-the-year, yearling lobsters, and larger EBP lobsters at the outfall compared to the inshore sites. Measures of the proportion of non-zero observations (which is another measure of frequency) for each size class also showed significantly fewer non-zero observations at the outfall. Taken together, these data demonstrate that while the cobble habitat at the vicinity of the outfall is suitable for settlement, it does not represent a major settlement site and thus there is no indication that the outfall will have any appreciable impact on these life stages of the American lobster.

Benthic Habitats of Boston Harbor and Nearshore Massachusetts Bay as Characterized by Sediment Profile Imaging
Robert Diaz
R. J. Diaz and Daughters, Ware Neck, VA

Long-term trends and status of benthic habitats in Boston Harbor and Nearshore Massachusetts Bay was characterized using sediment profile imaging. In 1992, annual surveys started in Boston Harbor and in 1997 in the Nearfield area, initial SPI surveys in these areas were conducted in 1989 and 1992 respectively. Sediment profile imaging provided a means of assessing benthic habitat quality by collecting visual data on dominant physical and biological processes that structure benthic communities. Key indicators of habitat quality (amphipod tube mats, Redox Potential Discontinuity layer depth and Organism Sediment Index) in the Harbor declined in 1998 relative to previous years, however, major changes in habitat quality appeared to have occurred prior to 1992. Current habitat quality has developed in response to major disturbance events in 1991, a severe storm in October and sewage discharge abatement in December. Stations with poorest habitat quality in 1992 continued to have poor quality in 1998 (T04, R43). The decline in amphipod tube mats may represent a negative rebound of Ampelisca spp. populations that continually increased from 1992 to 1996. This amphiod is an important indicator that occurs in high abundance in areas trending from poor to good habitat quality. When habitat quality improves to a certain point, a decline in amphiod tube mats is to be expected. Trends in Nearfield habitat quality appeared to be related to the physically dynamics of the area. Bottom instability maintains a patchy mosaic of habitat quality. In 1998 and 1999, biological processes dominated surface sediments at almost all stations with an increase in the degree of bioturbation.

Predicted changes in benthic habitat quality with the operation of the Nearfield discharge are:
Boston Harbor:

• Decline in Amphipod tube mats
• Transition to a Stage III benthic community
• Improved benthic habitat quality for inner harbor

Nearfield:

• Physical dynamics will control biological communities
• Periodic appearance of Amphipod tube mats
• Increase in epifauna

Lobster Contaminant Monitoring in Massachusetts and Cape Cod Bays
Lisa Lefkovitz and Carlton Hunt
Battelle Duxbury Operations, Duxbury, MA

Lobsters have been collected from Deer Island, the Massachusetts Bay Outfall Site and Eastern Cape Cod Bay since 1992 to evaluate general health and contaminant levels. Edible meat and hepatopancreas tissues have been analyzed for selected organics and metals. Results from these analyses are used to evaluate the potential human health exposure. Post-discharge results will be compared to the baseline period to determine if discharge from the outfall results in appreciable change from baseline values and to compare to the fish and shellfish monitoring thresholds. To date, chemical concentrations in edible meat for organics, such as PCBs and chlorinated pesticides, and mercury, have been highest in lobsters trapped near the present Deer Island outfall. The lowest concentrations are consistently found at the eastern Cape Cod Bay monitoring site. Hepatopancreas concentrations for organics show a similar trend. However, metals concentrations appear highest at the Outfall Site in Massachusetts Bay. Concentrations of most contaminants appear to have decreased since 1992 in both meat and hepatopancreas. The exceptions to this trend include silver in hepatopancreas tissue and PCBs and DDTs in both meat and hepatopancreas tissue at all locations. Metals concentrations have been much more variable than the organic contaminants among the sites over time. Concentrations measured throughout the baseline period were well below the monitoring threshold levels and human health consumption action limits.

Phytoplankton and Zooplankton of Boston Harbor, Massachusetts and Cape Cod Bays, 1992-1999, Within a Regional Context
Jefferson T. Turner, David G. Borkman, & Jean A. Lincoln
Center For Marine Sciences and Technology, Biology Department, University Of Massachusetts Dartmouth, Dartmouth, MA

Phytoplankton and zooplankton have been sampled in Massachusetts and Cape Cod Bays and Boston Harbor since 1992. Patterns of community composition, abundance and seasonality of phytoplankton and zooplankton in Massachusetts and Cape Cod Bays are variable in time, on scales from daily (within a survey), to monthly (between surveys), to interannual. Spatial patterns of community composition are generally similar within a given survey for areas outside Boston Harbor, but the Harbor is usually distinct from adjacent offshore areas. Plankton patterns both within Boston Harbor, and offshore in Massachusetts and Cape Cod Bays are generally similar to those in contiguous areas such as the upstream Gulf of Maine, and adjacent areas to the south such as Buzzards Bay, New Bedford Harbor, and Georges Bank.

Initial Effluent Dilution Verification and Plume Tracking Plan
By Carl Albro, Elizabeth Bruce, and Carlton Hunt
Battelle Duxbury Operations, Duxbury, MA
Rocky Geyer
Woods Hole Oceanographic Institution, Woods Hole, MA
Michael Mickelson
Massachusetts Water Resources Authority

This poster describes the proposed plume tracking surveys to determine that initial dilution characteristics of the outfall meet NPDES permit requirements, and track the longer-term location and mixing dynamics of the outfall plume to verify that the plume continues to disperse and does not travel intact to resource areas.

Assessing Temporal Changes in Highly Variable Fecal Coliform and Enterococcus Data in Boston Harbor and Its Tributaries by Randomized Block Factorial ANOVA
G. Gong and J. Lieberman,
ENSR, Inc., Acton, MA
D. McLaughlin
Massachusetts Institute of Technology, Cambridge, MA
A. Rex
Massachusetts Water Resources Authority, Boston, MA

The "Boston Harbor clean-up" is a multi-billion dollar public investment in major public works projects, including addressing wet weather pollution from combined sewer overflows (CSOs). Since 1989, MWRA has monitored fecal coliform and Enterococcus counts in Boston Harbor and its tributaries. Water quality is poorest during wet weather; CSOs and stormwater are the major sources of bacteria. If CSO controls are effective, then bacteria counts in wet weather will be lower than counts before CSO controls were implemented. Tracking environmental effects of pollution control projects is complicated by high variability in the data which make it difficult to interpret changes in bacteria counts over time. Rainfall, geographic location, season, salinity, temperature, and tide are all sources of variation. The purpose of this study was to develop and use a statistical method to answer the question, "Have fecal coliform and Enterococcus counts in these waters changed significantly over time?" Fecal coliform and Enterococcus counts from more than 8,000 water samples at 130 locations were included in the analysis. Preliminary regression analyses failed to detect statistically significant changes in the relationship between bacteria counts and rainfall over time. Factorial ANOVA with randomized blocking to partition the data and control for factors (location, tide, season) not contained in the ANOVA treatments (time and rain) detected significantly lower counts in the study area as a whole after some CSO controls were implemented. Decreases were significant for fecal coliform, but not Enterococcus.