Why study radiocesium
in fish from Steel Creek?
Risk assessment:
Potential risks exist for both humans and wildlife because
of the presence of cesium-137 in Steel Creek. For example,
cesium-137 may be transferred to humans consuming fish that
enter the Savannah River from Steel Creek delta. Likewise,
cesium-137 may be transferred to wildlife that consume fish
from this system. Most other isotopes of concern have decayed
away or have migrated from the creek. Research at Steel
Creek will be used to develop reliable risk assessments
for humans and wildlife, especially endangered forms.
Assessment of cleanup needs:
Data from research at Steel Creek will allow DOE to better
assess potential cleanup needs by providing baseline information
regarding the presence and availability of cesium-137 in
the aquatic food chain. In addition, newly collected data,
when compared with previous data, will allow determination
of the ecological half-life of cesium-137 in Steel Creek.
This, in turn, allows predictions to be made regarding the
future availability of this contaminant for uptake into
food chains. Much of the cesium-137 is no longer available
to biota in the creek.
Furthering knowledge in the field
of radioecology:
Research at Steel Creek will contribute to a better understanding
of the complex processes of bioaccumulation of cesium in
aquatic food chains and the “behavior” of cesium-137
in aquatic systems. This understanding should enable future
questions about radiocesium in fish to be answered more
easily and models for its dynamics to be constructed.
Past research
at Steel Creek
Previous research by the Savannah River Ecology Laboratory
(SREL) at Steel Creek focused on questions concerning cesium-137
levels in fish from the Steel Creek Corridor. During 1981,
cesium-137 levels were determined in fish and 
water
samples collected from four locations along the lower reaches
of Steel Creek between the delta and Highway 125. Results
of this earlier investigation provided valuable baseline
information regarding cesium-137 levels in fish that can
be used in future investigations.
Perhaps the most important finding of this investigation
was that the ratio of radioactivity in fish vs. radioactivity
in the creek water was much higher than had generally been
reported in other aquatic systems. This high “concentration
factor” (~3,000) was attributed to the soft water and
relatively low potassium levels in Steel Creek. In addition
to increased uptake of cesium-137, results also suggested
that bioaccumulation of cesium-137 occurred in fish from
Steel Creek, with top level predators like largemouth bass
having more cesium-137 than the fish they fed upon. Exposure
of wildlife depends, in part, upon the type of fish they
feed upon.
Current and
future research at Steel Creek
SREL researchers currently are determining cesium-137 levels
in several species of commercially and ecologically relevant
fish species collected from the Steel Creek delta and corridor
during January -- May 1998. The objective of this investigation
is to address the following questions concerning cesium-137
in fish from Steel Creek:
- What levels of cesium-137 currently are found in fish
from Steel Creek?
- What risk is associated with humans consuming fish from
Steel Creek?
- What risk is associated with wildlife consuming fish
from Steel Creek?
- What is the ecological half-life of cesium-137 in Steel
Creek?
- What is the magnitude of bio-accumulation of cesium-137
at higher trophic levels?
Several important species (i.e., species consumed by humans)
from the Steel Creek delta will be used in the development
of human risk assessments. Many of these species may migrate
between Steel Creek and the Savannah River. For select species,
the equation for the frequency distribution will be calculated
to predict the probability that a fish of a particular species
will have a given level of cesium-137. Along with information
about fish body size, these data will be used to determine
the risks to humans consuming fish from Steel Creek delta
Risk assessments for wildlife consuming cesium-137 contaminated
fish will focus on Wood Storks (federally endangered species)
and Bald Eagles (federally threatened species). These risk
assessments will be based on cesium-137 levels in several
ecologically relevant fish species (i.e., species consumed
by wildlife).
Levels of cesium-137 levels currently found in fish from
the Steel Creek corridor will be compared to cesium levels
in fish recorded during the 1981 SREL investigation to estimate
the ecological half-life of this radionuclide in the Steel
Creek system. Tissue from each fish also will be analyzed
to determine the ratio of stable nitrogen isotopes. These
ratios will allow each fish species to be assigned to a
trophic position within the food chains of Steel Creek.
Future research needs include the continuation and completion
of cesium-137 determinations and nitrogen isotope analyses
for fish that already have been collected. Furthermore,
additional fish of several different species will be collected
from the Steel Creek delta during the fall of 1998 to provide
adequate sample sizes for determining frequency distributions.
Samples from these collections also will permit analyses
for seasonal variation in cesium-137 levels and will be
available for future analyses to determine levels of mercury
in fish. The mercury data will be used to refine the risk
assessment calculations.
Deliverables
from research at Steel Creek
- An archived data set, including frequency distributions
of cesium-137 levels in fish species from Steel Creek
Delta that could be consumed by the public or wildlife.
- Risk assessments for humans and wildlife that might
be consuming fish from Steel Creek.
- Estimation of the ecological half-life of cesium-137
in the Steel Creek system.
- Contributions to the scientific community that include
an increased understanding of bioaccumulation of cesium-137
in aquatic food chains.
- Peer-reviewed publications reporting the results of
research conducted at Steel Creek.
- An informational brochure outlining risks associated
with fish consumption, to be distributed to the general
public.
Radiocesium in Fish from
Steel Creek 
(back to Research Snapshots)
