United States
Environmental Protection
Agency
Environmental Research
Laboratory
Narragansett Rl 02882
Research and Development
EPA/600/S3-87/011 July 1987
SEPA Project Summary
Physiological Impact of
Dredged Sediment on Two
Benthic Species
D. Michael Johns
\
Several international commissions
have recently called for effective short-
term biological response measure-
ments which can adequately detect the
effects of environmental concentra-
tions of contaminants. Such methods
must be relevant to ecological fitness
and must have predictive capability
value.
This report describes efforts to
develop a direct comparison of the
effects of Black Rock Harbor dredged
material on the bioenergetics of juve-
nile Nephtys incisa exposed in the
laboratory and of individuals obtained
in the field from a controlled disposal
of Black Rock Harbor material. Expo-
sure regimes used in the laboratory
studies were comparable to the expo-
sure environments that have been
predicted around the .BRH disposal site
in Long Island Sound. In addition the
effects of exposure to suspended BRH
material on the bioenergetics of the
mysid, Mysidopsis bahia were also
determined.
This Project Summary was devel-
oped by EPA's Environmental
Research Laboratory. Narragansett, Rl.
to announce key findings of the
research project that is fully docu-
mented in a separate report of the same
title (see Project Report ordering
information at back).
Introduction
The disposal of dredged material can
pose problems to the well being and
survival of benthic communities on or
near the site of disposal. Problems range
from the near complete but temporary
loss of the infaunal community at the
impact zone to the potential long-term
impact caused by the bioaccumulation of
contaminants from the sediments.
Further problems arise from the possible
effect on human health through biomag-
nification of toxic substances through the
food chain to edible commercial species.
The management of material through
ocean dipsosal becomes difficult at best
when one attempts to assess any even-
tual consequences to the environment
caused by the disposal of a particular type
of material. Predictive capabilities in the
form of a risk assessment are the
cornerstone of a sound ocean disposal
management plan. Risk assessment,
which is the integration of biological
effects and environmental exposure, is
a sequential assessment procedure
designed to provide the decision maker
with an estimate of the potential hazards
associated with a particular material.
A research plan of thistype is currently
being evaluated in a joint United States
Environmental Protection Agency and
Army Corps of Engineers research
program in which the effects of dredged
material from Black Rock Harbor (BRH),
Connecticut on a Long Island Sound
benthic species were assessed in the
laboratory prior to disposal operations.
Following disposal, a field study was
conducted to verify the response
observed in the laboratory and determine
the accuracy of the laboratory prediction.
This research program offers a unique
opportunity to evaluate the predictive
capacity of a variety of biological effects
tests.
Effective short-term biological
response measurements which can
adequately detect the effects of environ-
-------
mental concentrations of contaminants
recently have been called for by several
international commissions. In order to be
of value the measurements must have
some relevance to ecological fitness. In
addition, these laboratory effects tests
must have a predictive capability which
allows for the estimation of the degree
of ecological change which will take
place.
An effects measurement technique
which may satisfy the preceding criteria
is the determination of biological energy
balances along with its corrollaries,
including scope for growth. Previous
studies using these principles have found
a reasonable correlation between
changes in energy balances or scope for
growth and changes in population fit-
ness. The literature describes a series of
detailed field studies which found a
reduced scope for growth in My a are-
naria collected from oil-impacted sites
when compared to individuals from
nearby, relatively clean reference popu-
lations. These data were related to and
predictive of eventual changes in pop-
ulation structure which were observed
in the impacted sites. Changes in pop-
ulation structure that might relate to the
reduced scope for growth included
reductions in yearly growth rate and
populations density.
The final report describes efforts to
develop a direct comparison of the effects
of Black Rock Harbor material on the
bioenergetics of juvenile Nephtys incisa
exposed in the laboratory and on indi-
viduals obtained in the field from a
controlled disposal of Black Rock Harbor
material. Exposure regimes used in the
laboratory studies were comparable to
the exposure environments that have
been predicted around the BRH disposal
site in Long Island Sound.
In addition to the research conducted
with Nephtys incisa, the effects of
exposure to suspended BRH material on
the bioenergetics on the mysid, Mysidop-
sisbahia, were also determined. M. babia
is currently being used in the Field
Verification Program as a laboratory
surrogate for crustaceans that may be
found in and around the BRH disposal
site.
Discussion
Nephtys incisa
In a previous study reported in the
literature, Nephtys incisa juveniles
exhibited several responses when
exposed to BRH material under labora-
tory conditions. Changes attributed to
exposure to BRH sediment included
increased maintenance costs, reduced
tissue growth, weight loss, and lowered
net growth efficiency. Laboratory data
reported in this study confirm and extend
these findings.
The results of the present study
indicate that Nephtys incisa living in
relatively contaminant-free sediment
(REF sediment) are physiologically
affected by exposures to suspended BRH
particles. The bioenergetic effects of
suspended BRH material are evidenced
in some physiological processes during
the first 10 days of exposure when
differences in tissue production and
maintenance costs were noted. Con-
tinued exposure to BRH material does not
appreciably alter the types of physiolog-
ical changes observed in the worms but
rather magnifies the physiological effects
noted by day 10.
N. incisa are exposed to contaminants
entering the burrow system either in a
dissolved form or associated with par-
ticulates. Because of the high suspended
particle levels (200 mg/l) used in labor-
atory simulations, the contaminants
would be primarily associated with the
paniculate fraction. Polychlorinated
biphenyls levels monitored in the expo-
sure chambers during the experiments
indicate that approximately 98 percent
of the total PCB present in the water
column was associated with the panic-
ulate fraction. Furthermore, another
study reported that the only histological
abnormalities found in Nephtys incisa
exposed to BRH material in laboratory
experiments are thickening of the epi-
dermis and the appearance of macro-
phages containing black particles. They
concluded that the changes in epidermal
structure were due to direct contact with
BRH particles.
Field studies on Nephtys incisa indi-
cate a pattern of seasonal changes.
Significant differences in respiration and
ammonia excretion rates between sta-
tions occurred only during periods when
the water temperature was greater than
11°C. When water temperatures were
cooler, no significant differences in
weight specific respiration and ammonia
excretion rates were evident in individ-
uals collected from the various sampling
stations. Depending upon the time of
year, therefore, water temperature will
alter the apparent physiological effects
of exposure to BRH material.
A primary objective of the FVP was the
field verification of the results obtained
from laboratory simulations. Worms
collected from the BRH disposal site and
from the laboratory experiments exhib-
ited changes in physiological function
relative to increasing exposures to BRH
material. Since an exact match of expo-
sure environments between the labora-
tory simulations and field environment
could not be made, and because the
laboratory exposure environments
included higher concentrations of BRH
material than were present at the
disposal site, the laboratory findings
should be considered an upper bound
estimate for the effects of BRH sediment
on infaunal polychaetes.
Mysidopsis bah/a
As with Nephtys incisa, Mysidopsis
bah/a exhibited an exposure-dependent
response to suspended BRH material. All
physiological parameters examined
showed changes within six days follow-
ing the initial exposure. In additon to the
sublethal effects found at the lower BRH
level, 100% mortality was noted for
mysids maintained in the higher (> 50
percent BRH) levels.
Chronic exposure to BRH material
results in lowered growth rates in both
juvenile and early adult stages. These
reductions in growth can be attributed
to reductions in the average amount of
food ingested and to an increase in
maintenance costs. Reductions in energy
consumption levels were apparent by day
5 and persisted throughout the experi-
ment. The specific compounds causing
the reductions in food ingestion rates are
unknown; however, previous research
with single contaminants suggest that
neutral organics, rather than heavy
metals, are the causative agents.
Increased maintenance costs are a
generalized metabolic response to con-
taminant exposure. Regardless of the*
mechanism responsible, higher mainte-
nance costs reduce the amount of
assimilated energy available for growth.
The net result is that organisms faced
with higher maintenance costs will have
less energy (both quantity and quality)
which can be partitioned into growth
processes. Combined with the lowered
energy consumption rates found in
mysids exposed to BRH material, it is not
surprising that the higher maintenance
costs resulted in lower growth rates.
Changes in reproductive success could
be due to a variety of factors including
the failure of hormonal systems to
initiate egg maturation. Although such t
factors cannot be discounted, results of "
-------
the present study indicate that the
reproductive alterations were due, in
part, to the physiological dysfunctions
noted during earlier life history stages.
Changes in community and population
structure are the product of changes
occurring initially at the organism and
suborganism level. Although isolated
effects noted at the organismal level may
not translate into population changes
due to compensatory mechanisms, it is
evident that the sublethal changes seen
in this study do result in impacts at the
population level of organization. Impacts
on energetics of juvenile mysids result
in changes in secondary production and
in the intrinsic rate of population growth.
A similar conclusion cannot, at this time,
be drawn about bioenergetic dysfunction
noted with Nephtys incisa juveniles. N.
incisa populations from the BRH disposal
site sampling stations are currently being
analyzed through cohort analysis and
this data will provide an estimate of how
well the bioenergetic data predicted
eventual population impacts.
The responses of Mysidopsis bahia to
BRH material during the entire life cycle
indicate that bioenergetic dysfunction in
individuals preceded, and was predictive
of, changes at the population level.
Changes in growth, development, and
reproductive success can be directly
linked to alterations in energy balance
and on every flow noted in early juvenile
stages. Diversion of assimilated energy
to increased maintenance costs signif-
icantly reduced both the quantity and
quality of energy available for growth and
reproductive processes. The integration
of several physiological functions into a
bioenergetic index proved to be a sen-
sitive indicator of long-term effects
occurring at a higher level of biological
organization.
D. MichaelJohns is with Edgerton Research Laboratory, Boston. MA 02110..
Richard W. Latimer is the EPA Project Officer (see below).
The complete report, entitled "Physiological Impact of Dredged Sediment on
Two Benthic Species,"(Order No. PB 87-172 151/AS; Cost: $13.95, 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:
Environmental Research Laboratory
U.S. Environmental Protection Agency
Narragansett, Rl 02882
-------
United States
Environmental Protection
Agency
Center for Environmental Research
Information
Cincinnati OH 45268
ej.o.vrnv/tML.MMN.
PENALTY U.S.POSTAGf
£fvATF i
JSE $3oo) ; A 0 p ;
* » i _ U .i- (, _.
B METERi
-. u250IU3i
Official Business
Penalty for Private Use $300
EPA/600/S3-87/011
0000329 PS
U S ENVIR PROTECTION AGENCY
REGION 5 LIBRARY
230 3 DEARBORN STREET
CHICAGO IL 60604
------- |