United States
Environmental Protection
Agency
Chesapeake Bay Program
Annapolis MD 21401
Research and Development
EPA-600/S3-83-037 June 1 983
Project Summary
Animal-Sediment Relationships:
A Case Study of the Patapsco
River
Eli Reinharz
Extension of toxics-related research
from the main stem of Chesapeake Bay
into the estuarine tributaries is im-
portant for two reasons: (1) many sites
of industrial and domestic activity are
situated along the banks of these river-
ine systems, and (2) these subestuaries
may function as closed basins in terms
of sedimentation, trapping sediment-
borne toxicants. The objectives of this
study are to: (a) describe benthic com-
munity patterns in the Patapsco River
compared to a reference area, the Rhode
River, (b) characterize bioturbation
levels and sedimentary structures in
the two areas, (c) define sediment
deposition rates (via 137Cesium and
pollen) along both subestuaries, and
(d) define the histopathological condi-
tion of the bivalve, Macoma balthica,
throughout the estuarine systems.
Because of time constraints, sampling
was limited to the mid-spring of 1981;
a total of 18 sites was examined.
Based on benthic community patterns
in this and other studies, the Patapsco
River was divided into the following
environmental regimes: polluted (head
and peripheral branches), semi-polluted
(central region), and semi-healthy
(mouth). The Rhode River served as
the reference environment. Diversity
values increased toward the semi-hearthy
and reference areas. Generally, diver-
sity was low compared to the main
stem of the Chesapeake Bay. Most of
the benthic community was concen-
trated in the top 10 cm of the sediment
as in the main Bay. The deep-dwelling,
equilibristic community became more
significant in the gradient from polluted
to semi-healthy and reference regimes.
Porychaetous annelids proved to be
the most successful of the deep-dwell-
ing taxa.
Many of the samples manifested
some evidence of bioturbation. Physi-
cally dominated areas and associated
laminated sedimentary structures pre-
vailed in the polluted regime. In con-
trast, bioturbation in the semi-healthy
and reference environments had de-
stroyed all evidence of physically-pro-
duced features. This increase in bio-
turbation from* the head to the mouth
of the Patapsco River mimics the trend
in the main section of Chesapeake Bay.
Radionuclide (137Cesium) and pol-
len dating reveal that direct physical
mixing occurs at the sediment surface
in the unstable, polluted region. This
mixing may be the result of natural
and/or anthropogenic events. Biogenic
activities are principally responsible
for the observed sediment resorting in
the semi-healthy and reference areas.
The bivalve, Macoma balthica. was
collected in all environmental regimes
except the polluted area, where individ-
uals were too small to be examined for
significant pathological conditions.
Only a few diseased clams were found.
More diseased specimens are, however,
likely to occur in late summer when
stressed individuals are most suscep-
tible to infection.
This Project Summary was developed
by EPA's Chesapeake Bay Program,
Annapolis, MD, to announce key find-
ings of the research project that is fully
documented in a separate report of the
same title (see Project Report ordering
information at back).
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Introduction
Tributary estuaries of Chesapeake Bay
may support high concentrations of in-
dustrial and domestic activities. Further-
more, these subestuanes may function as
closed basins trapping sediment-borne
toxicants. The present study of a potential-
ly contaminated area, the Patapsco River,
was designed to augment similar research
conducted earlier in the main Bay.
The objectives of the study were to: a)
describe benthic community distribution
patterns in the Patapsco River compared
to a reference area, the Rhode River; b) to
characterize bioturbation levels and sedi-
mentary structures in the two areas; c) to
define sediment deposition rates and bio-
turbation in both areas; and d) to examine
the histopathology of the clam Macoma
balthica.
Procedure/Methodology
Eighteen sites were sampled during the
mid-spring of 1981: 15 sites in the Patapsco
River and three in the Rhode River. Box
core samples were taken using a U.S.
Navy Electronics Laboratory spade box
corer. Two box cores were taken at each
station: the first to sieve for benthic
organisms, the second for radio-graphic
processing sediment (grain size), 137Cesium,
and pollen analysis. Bottom salinity and
temperature were also measured
Benthic organisms were quantified by
sieving through a 0.5 mm mesh screen at
the following vertical intervals: 0 to 2 cm,
2 to 5 cm, and every 5 cm thereafter. All
individuals were fixed, preserved, and
stained for identification. Species counts,
diversity indices, and redundancy were
calculated for each station.
Core samples used in radiographic an-
alysis were prepared by refrigerating a 6
cm vertical slice and trimming core sections
to a thickness of 2 cm. Radiographs were
taken using a Tort 120 Kv medical X-ray
unit. Kodak AA-5 industrial X-ray film was
used.
Nine cores were dated using137Cesium
and pollen analysis, eight from the Patapsco
and one from the Rhode. Each core was
subsectioned as described above. One mL
of sediment was dried and acid-treated for
pollen counts. For137 Cesium analyses, a
subsample was oven-dried, weighed, and
analyzed on a Beckman gamma counter
for 2000 counts per sample. A New
England Nuclear 137Cesium standard and
multiple background counts were used to
quantify sample levels.
Macoma balthica clams were collected
by dredge from five sites in the Patapsco
River and two in the Rhode River. A
minimum of 50 clams per station was
collected. Three size classes were examined:
< 1 cm, 1 to 2 cm, and> 2 cm. Clams at
the head of the Patapsco were generally
smaller than the 4 mm dredge mesh size,
and these areas could not be analyzed
statistically.
Results/Conclusions
Spatial consistency in salinity, tempera-
ture, and sediment type was observed
throughout most of the Patapsco. Most of
the substrate consists of silts and clays;
higher variability observed in the head of
the estuary was attributed to dredging and
shipping activities.
Benthic community diversity increased,
while redundancy decreased, toward the
mouth of the Patapsco. In general, diversity
was low relative to the mam Bay. Only the
two outermost Patapsco stations had di-
versities comparable to the Rhode reference
area. Annelids were the dominant group
in the Patapsco, comprising > 90 percent
of the benthic community. In the Rhode
River, annelids were 39.2 percent of the
population, with anthropods (48.0 per-
cent) and mollusks (12.6 percent) also
important.
As in the mam Bay, most (> 95 percent)
of the benthic community is concentrated
in the top 10 cm of the sediment column.
There is a general increase in the number
of deep-dwelling individuals and species
in the gradient from "polluted" to "refer-
ence" environments.
Nearly all of the samples manifested
some evidence of bioturbation. The inten-
sity and frequency of physical disturbance
regulates benthic population patterns.
Physical processes dominate in the pe-
ripheral branches and head of the Patapsco;
in such highly disturbed areas organisms
cannot establish themselves long enough
to rework the sediment. Populations in the
polluted or disturbed areas of the estuary
are comprised mainly of emphemeral, sur-
face-dwelling, opportunistic species. In
the "semi-healthy" and "reference" areas,
bioturbation levels ere high due to a more
permanent deep-dwelling fauna. Here,
sedimentary structures are rarely observed
and the sediments are fairly homogeneous
137Cesium and pollen resorting indicates
that in unstable areas, direct physical mix-
ing occurs in the top 5 centimeters. This
may be due to natural forces of tides or
current, etc., or to anthropogenic causes.
Biogenic reworking is primarily responsible
for mixing in semi-healthy and reference
areas.
Few diseased Macoma clams were found
in the "semi-polluted," "semi-healthy,"
and "reference" areas. Because of the
small number and size of individuals in the
"polluted regime," potential pathogenic
conditions could not be assessed. The
greatest pathogenic effects are expected
to occur m late summer when stressed
clams are most susceptible to infection.
Such a follow-up study is highly recom-
mended.
Eli Reinharz is with The Maryland Geological Survey. Johns Hopkins University,
Baltimore, MD21218.
Gregory F. McG/nty is the EPA Project Officer (see below).
The complete report, entitled "Animal-Sediment Relationships: A Case Study of
the Patapsco River," (Order No. PB 83-207 001; Cost: $11.50. subject to
change) will be available only from:
National Technical Information Service
5285 Port Royal Road
Springfield, VA 22161
Telephone: 703-487-4650
The EPA Project Officer can be contacted at:
Chesapeake Bay Progam
U.S. Environmental Protection Agency
2083 West Street, Suite 5G
Annapolis, MD21401
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