Boston harbor's bad bottom: sediments: a resource in distress

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REPORT III.

Boston^s Bad Bottom -

Sediments: A Resource in Distress
November, 1988

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FOREWARD

The Boston Harbor Associates is pleased
to present "Boston Harbor's Bad Bottom:
Sediments - A Resource in Distress", the
third product of the Cleanup Action

Network .

TBHA has developed the Cleanup Action
Network, "CAN", to research and analyze
the technical and economic elements and
issues of Boston Harbor cleanup and to
provide this information in accessible
language for a broad audience. The
audience for "CAN" reports is TBHA ' s
Board of Directors, its business and non-
-profit organization alliances, an array
of elected and appointed officials with
whom TBHA works, the media and the
general public. It is our goal to
provide timely and accurate information
to serve as a basis for effective
advocacy for harbor cleanup.

I would like to thank the Bank of Boston,
Monsanto Chemical Co., Monsanto Fund and
Loomis Sayles for their support of the
Cleanup Action Network.

George Macomber

Chairman

The Boston Harbor Associates

ACKNOWLEDGEMENTS

This report is the third in a series from the
Cleanup Action Network. The report was prepared
under the direction of Daniel B. Curll, President
of The Boston Harbor Associates, by Michael P.
Shiaris, Biology Department, and Andrea C. Rex,
Environmental Science Program, at the University
of Massachusetts at Boston.

We gratefully acknowledge the assistance of
TBHA Board members Eugenie Beal, Valerie J.
Burns, Regina Harte Ryan, and Jay Kaufman who
reviewed drafts for readability and under-
standing. Cheryl Nelson of TBHA assisted in the
editing and production.

Any errors are the sole responsibility of the
authors .

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BOSTON HARBOR'S BAD BOTTOM

SEDIMENTS: A RESOURCE IN DISTRESS

Table of Contents

Executive Summary 1

Introduction 1

Sediment: A Primer

Physical and Chemical Properties 2

What are sediments 2

Sources, movement, and distributi'on of sediments 2

Sediment Biology 3

The benthos 3

Sediment as home: physical factors 4

Sunlight: the source of energy 4

Bacteria: the chemists of the sediments 4

Biological interactions in the benthos 5

Boston Harbor Sediments . 5

Boston Harbor sediments 5

Pollution in Boston Harbor sediments 6

Ecology of sediments in Boston Harbor 7

Effects of pollution on life in the Harbor 7

Interaction between sediment contaminants

and benthic organisms 8

Public Health Effects 8

Dredging 9

Can We Clean Boston's Sediments? 9

Clean-up 9

Recommendations 10

List of Scientific Issues 11

References 12

EXECUTIVE SUMMARY

Although in a degraded condition, Boston Harbor is a dynamic ecosystem;
potentially rich in resources, landscape, and beauty. Its sediments support the living
resources while absorbing the brunt of human pollution. This report reviews the nature of
Boston Harbor sediments, what they are, why they are a dynamic component of Boston
Harbor, what life they support, and how pollutants affect this precious ecosystem and
ultimately the humans who enjoy its resources. Scientific understanding of Boston Harbor
is inadequate and far less than for some other major harbors in the United States.

Marine sediment processes are complex, but they must be understood in order to
formulate and implement sound policy for pollution abatement. A comprehensive and
coordinated research effort is needed to provide a thorough understanding of Boston
Harbor as an integrated ecosystem. This effort should go hand-in-hand with a monitoring
program to ensure that implemented managerial programs are effective. This work would
be cost-effective: money spent on research and monitoring would be a small percent of the
overall pollution-abatement program. The management decisions necessary for designating
sewage outfall sites and selecting treatment alternatives require a fundamental
understanding of how Boston Harbor works. The $1.6 million earmarked for research
through the federal penalty and the Massachusetts Bay/Cape Cod Bay Program is a good
start, but only a beginning.

INTRODUCTION

The Boston Herald headline of April 28, 1987 proclaimed Boston Harbor the "Harbor
of Shame". The National Oceanographic and Atmospheric Administration (NCAA) has
deemed Boston Harbor the "most polluted harbor in the United States". The 1988
presidential race has placed national focus on Boston Harbor as a symbol of our imminent
environmental problems. Does the Harbor deserve the notoriety? A casual observer may
see only the natural beauty of the Harbor's waters and islands, but the problem lurks below
the surface.

NCAA, after conducting a preliminary survey of the condition of U.S. harbors,
based its conclusion on only a single sample and subsequent chemical analysis of Boston
Harbor sediments, the subject of this paper. The levels of key pollutants such as polycyclic
aromatic hydrocarbons (PAHs), poiychlorinated biphenyls (PCBs), the banned pesticide
DDT, and a variety of toxic metals, were the highest or near highest of any harbor
sediment examined in the NCAA study. NCAA's findings reinforce the observations of
citizens, scientists, and government agencies: the chronic accumulation of waste and
sewage in the Harbor has led to a severely polluted environment.

Should we be concerned that the sediments are polluted to such appalling levels?
After all, the contaminants are concentrated at the bottom of the Harbor, out of sight and
out of mind. The answer is yes. The sediments of relatively shallow waters such as
harbors and coastlines are the lifeblood of the system. They play a predominant role in the
well being of the overlying waters and all the living organisms which live in and around
the Harbor, including humans.

This report addresses Boston Harbor sediments. Sediments are integral to the
Harbor as an ecosystem, and must be considered in every aspect of future plans for the
Harbor. Our purpose here is three-fold; first, to provide a primer on the nature and role of
sediments; second, to examine the effects of chronic pollution on Boston Harbor sediments
and the implications to the ecosystem as a whole; and third, to evaluate options and
recommend steps for understanding the Harbor system, for managing the Harbor, and for
reversing the degradation of this valuable resource.

SEDIMENT: A PRIMER
PHYSICAL AND CHEMICAL PROPERTIES

What are Sediments? Webster's dictionary defines sediment as "any matter that
settles to the bottom of a liquid". Thus, the sediments of Boston Harbor are a complex
mixture of living and nonliving components: particles of minerals such as clays, quartz,
flint, chert, and feldspar, and organic matter (material derived from plants and animals
which include fats, sugars, and proteins or even particles of coal and coke ). The particles
range in size from the microscopic (clays to the larger silt particles) to large visible
particles (sand, cobble, pebbles, and boulders). The smaller particles, clays and silts, have a
great affinity for organic matter that is dissolved in the water, and become coated with an
organic film of fats, sugars, and proteins. This organic film has a great affinity for many
pollutants; which explains why some pollutants may be found in concentrations thousands
of times higher in sediments than in the overlying water.

Sources. Movement, and Distribution of Sediments. Boston Harbor is an estuary, a
partially enclosed body of water where freshwater meets seawater. In common with other
estuaries, Boston Harbor is a trap for sediment particles. Sediments accumulate over time,
constantly building up the bottom. Navigators and marina owners know all too well the
constant need to dredge the bottom as shipping channels and mooring areas fill up.

This influx of sediment particles has many sources. Particles are carried in by
rivers, streams, outfalls, and land runoff; by fallout from the atmosphere, by the erosion of
the adjacent coastline, by the resuspension of existing sediments, and by the creation of
new particles from the growth of living organisms within the harbor.

Estuaries also accumulate particles from the sea itself, although we tend to think of
the overall movement of water from land outward. This anomaly arises from the complex
patterns of water circulation distinctive to estuaries, as well as the small relative
difference in the force of ebb and flood tides. The landward flood tide carrying particles
from the sea reaches its peak at high slack tide as it pauses before returning to the ocean.
The stillness of the slack water allows more particles to settle. The return ebb tide tends to
be slightly less forceful, resulting in a heavy accumulation of sediments within the estuary.

Another important aspect of sediment formation is internal redistribution and
movement. Existing sediment particles can become resuspended into the overlying water by
a variety of processes. The force of the water moving over the surface of the sediment, if
great enough, can resuspend particles. These forces can vary daily with the tidal cycle,
with weather changes, with seasons, and with longer term cycles. A major storm or flood
can have a drastic long-term effect on the resuspension and formation of sediments. Also,
the microbes and animals living in the sediments affect the ease with which sediments can
become resuspended. The pervasive activity of tiny bacteria in the sediment leads to the
formation of slime material which binds the sediment particles, making them resistant to
resuspension. Similarly, animals living in the sediments ingest sediment particles and
excrete them, glued together as fecal pellets. Other animal activity such as burrowing may
have the opposite effect by enhancing the release of particles to the overlying water.

As its name suggests, sediment is derived from a constant rain of particles from the
overlying water. Larger particles, such as sand grains, fall out faster than the smaller clays
and silts. The rate at which the particles fall out from their water-suspended state depends
not only on their size but also on the velocity of the moving water. The faster the water
flow, whether by stream flow, tidal flow, or wind-driven movement, the longer the
particles remain suspended in the water. The ultimate outcome of this process is the
sorting of sediments by particle size. For example, in fast moving shallow channels the
sediments tend to be sandy or even bedrock. In quiescent deep holes, on the other hand, the
overlying water becomes still enough to allow the deposition of fine muds, often laden with
pollutants.

This process of particle sedimentation is also affected by the chemical nature of the
particles and surrounding water. One example of considerable importance to Boston
Harbor is the effect of organic matter. The large amounts of sewage-derived organic
matter dumped into Boston Harbor accelerates the deposition of suspended sediments . As
the organic matter sticks to individual suspended particles, it acts in a manner analogous to
a glazing of glue, resulting in the agglomeration of several particles which will drop to the
bottom faster than the individual particles. Therefore, the organic matter added to the
ecosystem from sewage causes particles laden with pollutants to sink rather than escape the
system in the tidal flow. The relative importance of different processes affecting
sedimentation in Boston Harbor is still being investigated. However, the consensus view of
several^oidies is that the major source of organic matter in Boston Harbor sediments is
sewage ,.

A detailed knowledge of particle interaction and water circulation patterns,
freshwater input from streams, runoff, and outfalls, is necessary to predictions of where
particles are likely to end up. Such an analysis is vital to rational planning for decisions
such as dredging for deepening shipping channels or constructing a new Harbor tunnel, and
deciding where to place new sewage outfall pipes.

SEDIMENT BIOLOGY

The benthos (from the Greek for deep). If you stroll along a beach below the high
tide mark, or explore a mudflat at low tide, you will quickly realize that the sand or mud
underfoot is alive! Innumerable small holes reveal the subsurface dwellings of clams and
worms. On a mudflat, piles of tiny round or cylindrical castings are the remains of the
worms' feeding activities. The mud is crisscrossed with the long, winding trails of
munching snails; while crabs and their smaller cousins, the bug-like amphipods, scurry and
hop across the flat in search of food. At times, the mud is gilded with the golden-brown
sheen of diatoms - microscopic plants which migrate to the surface, where they absorb the
sunlight necessary for photosynthesis. This complex community of bottom-dwelling plants
and animals is called the benthos, or benthic community.

The benthic community includes not only those creatures that are revealed to us at
low tide, but also those that are permanently submerged below the low tide line. The floor
of the entire World Ocean, from the edge of the sea to the deepest bottom trench; from the
tropics to the coldest parts of the Arctic, is teeming with life! Some important causes of
species' distribution and abundance in the benthos are: type of sediment (clay, silt, sand,
gravel, or rock), climate and local temperature, salinity, available nutrients, currents and
tides, as well as biological interactions. A burrowing worm cannot live on a rock, while a
barnacle has to cement itself to a solid surface.

One benthic environment that typically supports a very diverse group of organisms
is soft-bottom sediment. The most noticeable soft-bottom dwellers are large animals like
lobsters, crabs, sea urchins and snails that inhabit the surface of sediments: the epifauna.
The epifauna can move around to find food, or escape enemies and adverse environmental
conditions. But benthic communities include much more than these surface-dwellers. An
upturned shovelful of mud or sand will expose a multitude of creatures, the infauna, who
make their homes within the sediment. Many of these animals are beautiful and exotic,
like the polychaete (many-bristled) worm Pectinaria. the "ice-cream cone worm", builder of
an exquisite conical tube of perfectly-fitted sand grains, and the tiny jewel-like clam
Gemma: while others like the quahog and the soft-shelled clam are prized by people for
food. Infauna and epifauna that are visible to the naked eye (bigger than 0.3 millimeter -
the size of a sandgrain) are called the macrofauna. The macrofauna are far outnumbered
by a poorly-described group, animals so small that they live between sand grains: the
interstitial fauna or mciofauna. The meiofauna are comprised mostly of tiny worms,
nematodes, and minute shrimp-like creatures, harpacticoid copcpods, and larvae of other
species. Smaller in size than the meiofauna are the microfauna, mostly protozoans: single-

celled organisms. Tiniest of all are the microorganisms, including bacteria and fungi (yeast
and mold-like organisms). Microorganisms make up for their small size by their enormous
numbers: a thimbleful of bottom mud contains over a billion bacteria. In the benthos, ail
these forms of life live together in an interdependent way: they modify their environment
and their interactions can promote or inhibit the survival of various species in the
community. The benthos is a complex web of life, and the make-up of the community
depends both upon the physical environment and biological interactions .

What are these relationships, and what do these plants, animals, and microbes of the
soft-bottom benthos actually do in their muddy environment? Like those of us who live on
dry land, bottom-dwellers need a suitable place to live, and energy and nutrients to live
and grow.

Sediment as home: physical factors. The kinds of organisms found in a given
benthic environment depend in part on the nature of the sediment: whether muddy, sandy
or gravely, or rich or poor in organic nutrients. For example, fine-grained sediments like
muds often have poor water circulation and lower amounts of oxygen. Having less room
between sediment grains, they support fewer interstitial fauna. Muddy, silty sediments are
easily stirred up and resuspended in the water column, and therefore are unfavorable
environments for suspension-feeding animals. Such animals, like bivalve mollusks
(including quahogs and soft-shelled clams) and some amphipods, tiny crustaceans like the
beach flea, feed by straining water through filtering devices, catching particles on mucal
nets or in gills. The feeding apparatus of suspension feeders gets clogged up in muddy
waters. Other organisms are adapted to a muddy environments: the deposit feeders. Many
burrowing polychaete worms and snails belong to this group. The worms ingest the mud,
digesting any usable nutrients in the mud, and defecate the indigestible sediment grains.
Some deposit feeders, like snails, graze on the mud, selectively eating microalgae or
stripping bacteria off sediment particles. Generally, as the sediment becomes more sandy,
the percentage of suspension-feeders increases; and as the silt-clay proportion increases,
more deposit-feeders are found .

Sunlight: the source of energy. For the benthos, as for terrestrial life, the ultimate
source of energy is the sun, harnessed by plants through photosynthesis. In the marine
environment, tiny one-celled plants (microalgae) floating in the water, the phytoplankton,
carry out most photosynthesis. Benthic diatoms, types of microalgae that grow on the
sediment surface, are a major source of food to the other inhabitants of shallow waters.
The seaweeds like kelp (macroalgae) can also be an important food source where they grow.
Like all plants, their growth depends on the amount of sunlight and fertilizer (nitrogen and
phosphorus); the latter an important ingredient of sewage.

Phytoplankton are grazed by tiny animals floating in the water, the zooplankton.
These zooplankton are primary consumers. They in turn are eaten by animals like fish fry
and jellyfish. In relatively shallow water, dead phytoplankton and zooplankton can settle
out to the bottom; but the primary contribution of phytoplankton as a food resource for the
benthos is in the form of fecal pellets produced by the zooplankton. The fecal pellets sink
rapidly to the bottom, where they can be consumed directly by benthic animals or
decomposed by bacteria. The bacteria themselves are eaten by benthic animals.

Bacteria: the chemists of sediments. Microorganisms, particularly the bacteria, are
a food source; but they have other critical roles in the benthos. Bacteria decompose the
organic material that arrives on the bottom, converting the organic matter to carbon
dioxide. Bacterial metabolism is important in the chemistry of sediments, and has great
effect on the amount of oxygen in the sediments. The "sulfur cycle" is particularly
important in marine sediments. Sulfates are abundant in seawater, and are also derived
from the proteins of dead plants and animals. Some anaerobic (organisms that do not use
oxygen) bacteria convert this sulfate to hydrogen sulfide. This poisonous gas produces the
characteristic "rotten egg" smell of marine sediments at low tide and black color of the
lower layers of marine sediments. Many aerobic (oxygen-respiring) faunal species cannot

live in this black, sulfide-rich zone unless they have some means of obtaining oxygenated
water, such as a tube reaching above.

Bacteria also control the recycling of other important nutrients, like nitrogen and
phosphorous from seawater and dead organic matter.

The amount of oxygen available in sediments is related to bacterial activity and the
amount of organic material in the sediments. Normal sediments have easily discernable
layers: a lighter brownish-gray oxygenated surface layer overlying a black, anaerobic
layer. The depth of the oxidized layer depends on the type of sediment (porous sediment
having a thicker oxygenated layer), and the amount of organic material available. Aerobic
bacteria use up oxygen when they decompose organic matter. If the amount of organic
matter is overabundant, all the oxygen can be rapidly depleted by bacteria, making the
sediment totally anaerobic and black, even at the normally oxidized surface layer. This
kind of anaerobic environment is inhospitable to most benthic animals.

Biological interactions in. the benthos. So far, we have touched on some of the
physical factors, like sediment type, and some biological processes like primary production,
nutrient cycling and decomposition that can influence the composition of the benthic
community. But biological interactions among the inhabitants of the benthos are equally
important. As on dry land, the animals of the benthos modify their environment as they
make their homes, feed, excrete, and reproduce. Benthic animals compete for resources,
both with their own species and with other species. Predator-prey interactions are also
important in determining the community structure, or what kinds of animals, coexist in a
given environment.

One important ecological interaction is competition. Species compete for food and
for space to live. For example, if two species require the same limited food resource, and
one of those species can exploit the resource more efficiently, that species can exclude the
other.

Diversity, the number of species in a community, can be influenced by predation.
Predators, like crabs, fish, and some worms catch and eat other animals. Predation can
decrease the density of prey animals, and alleviate competition among the prey for food
resources. This alleviation of competition can permit more species to coexist in a given
environment.

An important example of biological activity in the benthos is bioturbation. Animals
that live in tubes extending deep into the bottom or that burrow around in the sediment
alter their environment by 1) bringing oxygenated water deep into the sediment and 2)
constantly "reworking" the sediments, bringing sediment from below to the surface, and
vice-versa, a deeper oxygenated layer permits other animals to live below the surface, and
increases the area of sediment subject to aerobic microbial activity and decomposition.
More nutrients are thereby mobilized and made available to the ecosystem. Similarly, when
deeper sediments are brought to the sediment surface, previously buried nutrients can be
used by the surface creatures.

Bottom-dwellers live in a complex spatial and temporal mosaic. For example, it is
common to find a dense patch of tube-dwelling worms. This patch of worms may interact
with other species in different ways: 1) by taking up space, prevent the settlement of
larvae of other species; 2) be eaten by predators, or die, creating new space for colonizers
3) actually facilitate the colonization of other species by stabilizing the mud.

BOSTON HARBOR SEDIMENTS

Boston Harbor sediments. Boston Harbor as with all New England coastal zones, is a
relatively young geographical formation, born 12,000 to 14,000 years ago with the end of
the last ice age. Since that time, sediments have been gradually accumulating. Through
analysis of buried layers, it may be possible to reconstruct the climate and vegetation
history of the area, the rates of normal deposition, historical rates of pollutant input, and

the effect of increasing pollution load. Because the sediments of Boston Harbor
accumulate with time, they retain a physical diary of past events; each lower layer a record
of an earlier time. This history is not always complete since storms can wash away records
or sediment-burrowing animals can mix the records up. Still, in relatively undisturbed
sediments, it is possible to analyze chemicals or the remains previous life (such as pollen) to
reconstruct the history of deposition in the harbor. A relevant example is the work of
Michael Fitzgerald-*. He showed that the sediment records in Deer Island Flats, near
Logan Airport, display an elevation in toxic metals corresponding to the point in time,
1936, when Shirley Gut was closed. Shirley Gut was a connection of Boston Harbor to
Massachusetts Bay between Winthrop and Deer Island. Clearly, the closing of Shirley Gut
altered the pattern of water circulation and resulted in the accumulation of metal-laden
suspended particles in an area. Deer Island Flats, which was not impacted prior to the
human intervention in the flow of water.

The bottom of Boston Harbor is a mosaic of differing patches of sediment types,
ranging from muds composed of fine clays and silt to sandy bottoms to rock outcroppings.
Some sediments are relatively uniform in size, for example, the Boston blue clay layer
which was laid down soon after the last glaciers receded to the North thousands of years
ago. However, variable mixtures of sizes are more typical. Sampling of Boston Harbor has
revealed this great variability in sediments, but until now a detailed map, vital for
understanding the processes working in the Harbor, has not been available. However,
scientists from the U.S. Geological Survey are currently preparing such a map. As will be
discussed below, a detailed map of the bottom type provides important evidence of how the
bottom is formed, what forces are at play, what are the sources of particles and pollutants
to the Harbor, and ultimately aiding in deciding what may be the best strategies to manage
the Harbor.

Pollution in Boston Harbor sediments. Just as Boston Harbor is a trap for sediments,
the sediments in turn act to trap many pollutants. The fine-grained clays and silts with
their coats of organic matter, in particular, actively collect pollutants from surrounding
water and concentrate them in the sediments. For example, at Deer Island Flats next to
Logan Airport, where the water circulation patterns are complex, there are enclaves where
gyres, or circular patterns, and slow water movement allow buildup of fine sediments -
"pockets of pollution"-'. In contrast, the bottom directly adjacent to the Deer Island outfalls
has much lower amounts of fine particles and pollution because of the scouring action of
the swift-moving currents in the relatively narrow channel. The pollutants of concern
which display this proclivity to bind to fine sediments and suspended particles have
become household names in the past 20 years: pesticides such as DDT, herbicides such as
2,4-D, products of combustion such as polycyclic aromatic hydrocarbons (PAHs),
polychlorinated biphenyls (PCBs), oil, grease, gasoline, and toxic metals such as cadmium,
lead, zinc, chromium, tin, copper, and mercury. These toxins originate from human
activity, both domestic and industrial. They enter Boston Harbor in many ways; from
sewage outfalls, sludge pipes, combined storm outlets, land runoff, streams feeding the
Harbor, leaching of dump sites, and atmospheric fallout.

In the case of Boston Harbor, the relative contribution of each source to the total
load of pollutants entering the Harbor is not well known. Establishing the relative
importance of these sources is vital for abating pollution in the Harbor. The sewage
treatment plant outfalls certainly contribute a significant amount of pollution, but how
important are other sources? For example, scientists suspect that most lead in the Harbor
arises from automobile exhaust and falls out from the atmosphere.

The pollutant load in Boston Harbor is egregiously high. Sediment pollutant
analyses have been performed. Unfortunately, most sediment analyses have been
conducted in an ad hoc manner by independent groups in order to address the
environmental impact of specific local construction projects. This has resulted in a very
fragmentary understanding of the extent and distribution of various pollutants. The story
is incomplete for other reasons. Much of the existing data is old and was gathered by
outdated and inaccurate techniques. The monitoring efforts have not been coordinated

among various groups to yield data useful beyond the narrow scope of the impact
assessment. In spite of these limitations, the knowledge that we have supports the
preliminary "most polluted harbor in the United States" report of NOAA A more
comprehensive survey of PAHs in Boston Harbor sediments, for example^, indicates gross
contamination of Inner Harbor and Moon Island sediments, with levels as high as any
reported in the scientific literature, even Tokyo Bay, Japan. The implications of high PAH
contamination are ominous. Many PAHs are carcinogenic, and their high concentrations
may help explain the high incidence of tumors in the flounders caught in the Harbor .

Ecology of sediments in Boston Harbor. A variety of habitats and biological
communities are found in Boston Harbor. Saltmarshes (Belle Isle Marsh, the Neponset
River marsh, on Thompson Island and in Hingham Harbor), are net exporters of nutrients,
play an important role in fish reproduction, and are sanctuaries for many animal species.
Hard or rocky bottom environments (the Graves, the Brewsters, even pilings) are home to
starfish, barnacles, and mussels. But the most extensive and important habitat in the
Harbor is soft-bottom sediment. Acres of mudflats, from Bird Island flats near the airport,
to mudflats along the Neponset River, besides receiving the brunt of pollution also support
shellfish, worms, benthic diatoms, and often shore birds. Beneath the low tide line, the
species found include predominantly worms, bivalve mollusks. and some small crustaceans.
Kelp beds grow in the deeper waters of the Harbor, grazed upon by sea urchins. Bottom-
feeding fish eat these various benthic species.

In Boston Harbor, where the waters are quite shallow, there is a very close coupling
between processes in the benthos and the water above, or water column. Dead plankton, as
well as fecal pellets, reach the bottom quickly; while sediments stirred up by bioturbation,
and invertebrates fed upon by fish make their contribution to the overlying water.

Effect of pollution on life in the Harbor: community structure. The pollution
entering the harbor ecosystem is of a dual nature: the first is outright toxicity, from
chemical poisons, (including the chlorine used in sewage treatment);and the second is
"nutrient loading", mostly from domestic sewage. This includes a large input of carbon,
nitrogen, phosphorous and sulfur; important nutrients for natural communities.

In the same manner as organic-coated sediment particles absorb toxic pollutants,
phytoplankton and zooplankton also concentrate pollutants from the water. The pollutants
make their way to the bottom packaged in fecal pellets after being digested by the small
animals.

Toxic contaminants affect some species more than others. Often one of the most
immediate effects of toxics on the benthic community is on predators: many predators are
very sensitive to toxic effects, and are either killed off or leave. If a keystone predator is
removed, the remaining animals increase in density, and compete more directly for food or
space resources. This leads to reduced diversity of the prey species and disintegration of
the community. Many parts of the Boston Harbor benthos, particularly large areas of the
Inner Harbor, are now almost exclusively composed of a classical "pollution indicator"
organism, the worm Capitella. A study done correlating levels of metals in Harbor
sediments with benthic species diversity showed that decreased benthic diversity
corresponded to increased concentrations of metals'*. The decline of benthic diversity
affects non-benthic organisms as well. For example, fish with specialized diets, feeding on
only certain components of the benthos, may be left without food resources.

Acute toxicity and death of animals are not the only effects of pollution. More
subtle, long-term effects have been observed in a variety of aquatic environments. Genetic
deformities, impaired reproduction and development, reduced growth, and cancer-like
diseases (neoplasi^as) have been documented in worms and shellfish in Oregon, Chesapeake
Bay, and Maine . In Boston Harbor, the bottom-dwelling winter flounder shows a high
prevalence of fin rot and liver cancer . This may be related to the high levels of aromatic
hydrocarbons, or to a combination of the many pollutant insults; however, the exact
components of pollution responsible for chronic ailments in Boston Harbor are complex
scientific questions and as yet unknown.

Nutrient loading of sediments from domestic sewage can also have a devastating
effect on the benthos. In Boston Harbor, an enormous proportion of the organic matter
comes from sewage, not just algal photosynthesis. This excess production can have the
effect of eutrophicatioQ, a process which leads to depletion of available oxygen by bacteria
metabolizing the copious organic matter. This results in anaerobic sediment, essentially
devoid of higher life. Another effect that the input of excess nutrients has is to favor only
a limited number of benthic species, pollution-tolerant animals, who outcompete the normal
diverse residents.

Interactions between sediment contaminants and benthic orRanisms. The sediment is
often thought of as a "sink" for nutrients and pollutants, where they are buried and taken
out of circulation. However, benthic animals interact with contaminants in sediments in a
number of ways which result in the transfer of contaminants to other components of the
ecosystem. Benthic organisms can bioaccumuiate pollutants by ingesting the sediment.
These contaminants are transferred up the food chain when contaminated benthic
organisms are eaten. This can result in biomagnification effects, where animals higher up
in the food chain develop higher concentrations of the pollutant in their tissues. (The
increased mortality of eagles and hawks caused by DDT is an example of biomagnification.
The DDT was not excreted by the birds that consumed it in their prey, but accumulated in
fatty tissue, where the chemical interfered with egg shell formation.) Benthic organisms
move in and out of contaminated sediments, redistributing the pollutants. Benthic
invertebrates can metabolize, or biodcgrade contaminants. This process is beneficial for
the environment if it leads to the removal of the pollutant, but and unfortunately for the
victim, metabolism of many organic pollutants by higher animals often converts relatively
inert chemicals into potent cancer-causing agents. The stirring up and reworking of the
sediments by burrowing worms and bivalve mollusks is another important way
contaminants can be reintroduced into the overlying water column.

Bacteria play an important role in mobilizing pollutants. Metals, like mercury and
tin are methylated by bacteria, a process which changes the chemical structure of the metal
by adding an organic ingredient to the metal. In their methylated form, metals are more
toxic and more easily absorbed by organisms, increasing their transfer up the food chain
and biomagnification.

One paradoxical effect can be anticipated in Boston Harbor. As pollution
abatement gets underway, the nutrient loading of the sediments will decrease, oxygenation
will increase, augmenting bioturbation. This may actually result in temporarily increased
levels of contaminants in the water, as animals exacerbate the release of contaminants now
bound up in the sediments.

Public health effects. Humans are consumers at the top of the food chain, most
susceptible to the effects of biomagnification of toxics. Studies in other environments, for
example the Great Lakes, have shown that people who eat large amounts of fish have
elevated PCB levels in their tissues. No studies have been done on consumers of Boston
Harbor fish or shellfish.

We have known for centuries that sewage carries infectious diseases. Public health
agencies have long made efforts to monitor sewage-impacted waters. Swimming beaches
and shellfish beds are classified as safe or unusable on the basis of coliform (bacteria
normally found in mammalian intestines) counts in the waters. (These subjects were
treated in Cleanup Action Network Reports I and II.) Scientific studies show much greater
numbers of disease-causing organisms and their indicators in sediments than the overlying
waters. This is because bacteria accumulate in, and are protected by, sediments. One study
in a Boston Harbor sedinient showed 10,000-fold higher numbers of coliforms in the
sediment than the water . Polluted sediments are known to be a reservoir of disease-
causing microbes.

Sediments accumulate toxic materials. Boston Harbor beachgoers, especially small
children, who play in the sand and mud, stir up the bottom, and swallow more seawater
than do adults, put themselves in direct contact with all the accumulated toxic materials

discharged by the sewer system of a major metropolitan area. It is known that some
organic contaminants can be absorbed through the skin, but the health risk of bathing at
Boston Harbor beaches has not been studied.

Finally, aesthetic concerns in the pollution of Harbor sediments are of great
importance, as attempts are made to reclaim this resource. It would be difficult to
overestimate how valuable it would be, both to the mental health of the citizens, and the
attractiveness of the city to business, to have an accessible, well used, aesthetically pleasing
waterfront.

Dredging. Dredging, the process of digging up sediments and moving them
elsewhere, has a major impact on sediment processes and distribution. Dredging is
necessary for maintaining shipping channels, marinas, ports, and recreation areas. Major
waterfront construction projects also require massive dredging operations. The need for
dredging in Boston Harbor is clear: Boston Harbor is the largest seaport in New England,
handling over $2 billion in foreign trade annually (Task Force, CZM). Already, several
major dredging projects have been planned for the next 15 years. An estimated 7.7 million
cubic yards of material will be removed for disposal in the open ocean; however, up to 10%
of the dredged sediments, called dredge spoil, may not pass the EPA's pollution standards
for open ocean disposal .

Dredging may have severe impacts on the adjacent area. The major impact is due to
the extensive resuspension of sediment particles clouding the water (turbidity). While
turbidity may be fairly local, the finer grain clays and silts which do not settle very
quickly can travel far, often miles, from the source. In the turbid area, the resulting
blockage of light may inhibit algae and plants which are a major food source of estuarine
animals. The resuspended and settling particles may also alter the habitat of many benthic
animals by a variety of mechanisms. Outright dislocation and burial of animals is the most
obvious mechanism. Less obvious but important impacts of dredging on benthic animals
include impaired breathing and feeding, disruption and clogging of gills, and retarded egg
development. Of course, if the particles are heavily contaminated, the pollutants will be
transported downstream by currents and partially released to the overlying water.

CAN WE CLEAN BOSTON'S SEDIMENTS?

Clean-up. The public interest (and the requirement of the federal Clean Water Act)
is to restore Boston Harbor to a healthy state conducive to fishing, shellfishing, boating,
and swimming. The impending effort is to expand and improve the sewage treatment
process and thereby reduce the amount of sewage entering Boston Harbor. This will clearly
slow down or halt further deterioration of the Harbor, but will cessation of sewage
dumping be adequate to restore the Harbor to a "clean" condition? Unfortunately, even if
all the sources of pollution to Boston Harbor were abated, the Harbor would take decades
to recover. The sediments themselves would become the major source of pollution to the
overlying waters, although the rate at which individual contaminants might be released
again to the water is conjectural.

There are natural or "self-cleaning" processes that work to lower the contamination
levels in surface sediments; including 1) tidal action which continually fills and replaces
the overlying waters, and 2) bioturbation, but many pollutants resist microbial attack and
bind tightly to sediment particles. Therefore sediment-bound pollutants will be removed
by tides or bioturbation slowly. The toxic metals, for example, cannot be removed from the
Harbor by microbial activities. So without human intervention other than halting sewage
dumping, the decades-long burial and dilution of contaminated sediment by fresh clean
sediment particles will greatly outweigh removal by tides and microbial decomposition.

Perhaps we could take advantage of clean-up or remediation technologies to hasten
the recovery of Boston Harbor. For example, the most contaminated sediments could be
relocated to deep ocean sites or landfills. Effective but exorbitant technologies can

detoxify the sediments by passing them through special furnaces. Other options are to
sequester the contaminated sediments by covering them with clean sediment or impervious
liners or to plow the sediments to stimulate microbial degradation of the pollutants.

In extensive areas, such as Boston Harbor, remedial action may not be a reasonable
alternative. It may be better to leave sediments in place and let natural mechanisms take
their course. However, if "hot spots" which contain levels of pollutants that are a
continuing threat to the harbor resources are identified, some remedial action may be
required. The choices are many and they are costly but a detailed knowledge of the
pollution^ ^ must be established first. Therefore, the problems unique to Boston Harbor
must be identified and assessed. Only then can one decide if remedial action is warranted,
which options are reasonable, and which options are cost-effective for Boston Harbor. As
we have discussed previously, not enough information exists on Boston Harbor pollution to
adequately identify the problem areas.

Recommendations. This review of Boston Harbor stresses the need for
understanding the source of sediments, how they move about, how they transfer nutrients
and pollutants to the overlying water, their effects on the plants and animals, and what
steps to take to eventually cleanse them of pollutants. We recommend a comprehensive
research program to develop a more complete understanding of the Boston Harbor
ecosystem.

The National Research Council (NRC) in 1983 addressed the problem of coastal and
estuarine pollution . Their primary message was the need for an interdisciplinary
approach, involving biologists, chemists, physicists, and mathematical modelers among
other experts, to fill in the gaps in our knowledge. The NRC stressed the need for basic
knowledge in three key areas: 1) the effect of pollutants on plants, animals, and
microorganisms, 2) an understanding of water circulation and mixing in estuaries, and 3)
the dynamics of suspended particles and dissolved matter in the overlying water.

Successful integrated studies of physical and biological environments of other urban
estuaries, for example San Francisco Bay and the Chesapeake Bay, have been carried out.
When the perennial questions and ensuing decisions regarding Boston Harbor arise,
decision-makers often lack scientific knowledge. Instead of regulatory decisions based on
scientific understanding providing rational options, decisions are often made for politically
expedient reasons.

We recommend that a systematic, interdisciplinary scientific study of Boston Harbor
be initiated. As a first approach, all the scientific knowledge which has accumulated
piecemeal over the years should be collected, centralized, and examined critically to glean
out the useful information. Simultaneously, a collection of basic information which is
fundamental to describing the Harbor should be garnered by coordinated research and a
rigorous monitoring effort. The monitoring is most important to ensure that the abatement
efforts are effective. This information should be useful to developing a model of Boston
Harbor processes. Predictive models are useful to regulatory agencies in estimating the
potential effects of alternative actions on the Harbor. Models can be used to test the
outcomes of different management strategies with the best available knowledge.

This research effort should be long-term, gradually encompassing other needs and
questions. For example, how long do different pollutants stay in Boston Harbor sediments,
how do they affect animal life, and what environmental factors affect the fate and
removal of pollutants? A summary of the pressing scientific needs is given below. The
result of such a plan would be an increasingly refined understanding of how Boston
Harbor works. In the long run a comprehensive study would be cost-effective, saving the
taxpayers of the Commonwealth the large cost of taking actions after the damage has
become even more unwieldy. For example, a pressing issue now is where should the sewage
effluent pipe be located? If a basic understanding of the Boston Harbor ecosystem existed
as outlined below, it would provide clear answers to most of the scientific questions that
cannot be answered with any good degree of certainty now. For example, how much of the
material would return to the Harbor? What effect would the effluent have on the natural
resources at the pipe or a given distance away from the pipe? Other issues that would

10

benefit from a solid understanding of the Harbor include the effectiveness of sewage
treatment options, the disposal of dredge spoils, the Fan Pier project, the third harbor
tunnel project, and other future development projects on the Boston Harbor shoreline.
The most important result of a comprehensive understanding of Boston Harbor
would be the accelerated reversal of pollution and degradation of this important aesthetic,
recreational, and economic resource.

Among the most important scientific issues that should be addressed immediately for
Boston Harbor, Massachusetts, are the need to:

1. Determine the complex circulation patterns in Boston Harbor and Massachusetts Bay.

2. Determine the exchange of water, nutrients, and pollutants between Boston Harbor and

Massachusetts Bay.

3. Develop a model to explain and predict circulation in Boston Harbor and Massachusetts

Bay.

4. Describe in detail the pollutants (chemicals and disease-causing agents) in the water and

sediments, their distribution, and their primary sources to the Harbor.

5. Determine the fate of these pollutants and disease-causing agents in Boston Harbor, and

what factors are most important in their removal from the Harbor.

6. Determine how sediments are redistributed as a result of tidal currents and episodic

storms, and identify the processes which control this movement.

7. Analyze in detail the plants and animals in Boston Harbor to determine types, numbers,

seasonality, and distribution within the Harbor.

8. Develop an understanding of how the different plant and animal species interact with

each other and with the variations in circulation and chemistry.

9. Establish long-term research goals to consider how natural stresses and pollution affect

those interactions and the general structure and function of the Boston Harbor
ecosystem.

10. Initiate a well-planned monitoring effort to follow the progress and effects of

implemented managerial programs.

Again, we emphasize that the strength of this proposed study would be in its
coordinated and interdisciplinary form. This is in direct contrast to the hodgepodge and
ad hoc nature of the studies conducted to date.

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REFERENCES

1. BARR, B.W. 1987. Dredging Handbook, A Primer for Dredging in the Coastal Zone of

Massachusetts. Massachusetts Coastal Zone Management, Boston, MA

2. DYER. K.R. 1986. Coastal and Estuarine Sediment Dynamics. John Wiley & Sons, New

York.

3. FITZGERALD, M.G., J.D. MILLIMAN, and M. BOTHNER. 1980. Source and fate of

urban estuarine sediments. 1979-1980 Annual Sea Grant Report, Woods
Hole Oceanographic Institute, Woods Hole, MA.

4. GRAY, J.S. 1981. The ecology of marine sediments. Cambridge University Press. New

York. 185pp.

5. HALL, M. 1986. Masters Thesis. University of Massachusetts-Boston.

6. MENCHER, E., R.A. COPELAND, AND H. PAYSON, JR. 1968. Surficial sediments of

Boston Harbor, Massachusetts. J. Sedim. Petrol. 38:79-86.

7. MURCHELANO. R.A. and R.E. WOLKE. 1985. Epizootic carcinoma in the winter

flounder. Pseudopleuronectes americanus. Science 228: 587-589.

8. NATIONAL RESEARCH COUNCIL. 1983. Fundamental Research on Estuaries: The

importance of an Interdisciplinary Approach National Academy Press, Washington,
D.C.

9. SHIARIS, M.P., and D. JAMBARD-SWEET. 1986. Polycyclic aromatic hydrocarbons in

surficial sediments of Boston Harbor, Massachusetts, USA. Mar. Pollut. Bull. 17:469-

472.

10. SHIARIS, M.P., A.C. REX, G.W. PETTIBONE, K. KEAY, P. McMANUS, M.A. REX, J.

EBERSOLE, AND E. GALLAGHER. 1987. Distribution of indicator bacteria and
Vibrio parahaemolvticus in sewage polluted intertidal sediments. Appl. Environ.
Microbiol. 53: 1756-1761.

11. THOMAS, R.L. 1987. A protocol for the selection of process-oriented remedial options

to control in situ sediment contaminants. Hydrobiologia 149:247-258.

12. THOMAS, R.L., R. EVANS, A. HAMILTON, M. MANAWAR, T. REYNOLDSON, H.

SADA (EDS). 1987. Ecological effects of in. situ sediment contaminants. In
Hydrobiologia 149. Dr. W. Junk Publishers, Dordrecht. Netherlands.

13. WHELAN, J.K. 1980. Influence of sewage outfall, storm sewers, and tides on organic

particles. 1979-1980 Annual Sea Grant Report, Woods Hole Oceanographic Institute,
Woods Hole, MA.

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