Responses of benthic fish exposed to contaminants in outdoor microcosms-examining the ecological relevance of previous laboratory toxicity tests
W.A. Hopkinsa,b,*, B.P. Staub a, J.W. Snodgrassa,c,
B.E. Taylora, A.E. DeBiase a, J.H. Roea,
B.P. Jacksona, J.D. Congdon a
a Savannah River Ecology Laboratory, University
of Georgia, Drawer E, Aiken, SC 29802, USA
b Department of Biological Sciences, University of South Carolina,
Columbia. SC, USA
C Department of Biology, Towson University, Towson, MD, USA
Received 2 May 2003; received in revised form 21 January 2004; accepted 21 January 2004
Abstract
Previous laboratory studies indicate that coal combustion wastes (a mixture
composed of fly ash and other lower volume wastes such as bottom ash;
hereafter collectively referred to as ash) adversely affect the health
of benthic fish (Erimyzon sucetta; lake chubsucker), but fish
in these studies were provided with ample uncontaminated food resources.
Because aquatic disposal of ash can also adversely affect food resources
for benthic fish, we hypothesized that changes in resources might exacerbate
the effects of ash on fish observed in laboratory studies. We exposed
juvenile E. sucetta in outdoor microcosms to water, sediment,
and benthic resources from an ash-contaminated site or a reference site
for 45 days and compared our findings to previous laboratory studies.
Benthic invertebrate biomass was nearly three times greater in controls
compared to ash microcosms. Total organic content of control sediment
(41%) was also greater than in ash sediments (17%), suggesting that additional
benthic resources may have also been limited in ash microcosms. Benthic
invertebrates isolated from the ash microcosms had trace element concentrations
(As, Cd, Co, Cr, Cs, Se, Sr, and V) up to 18 times higher than in weathered
ash used in laboratory studies. The concentrations of trace elements accumulated
by fish reflected the high dietary concentrations encountered in the ash
microcosms and were associated with reduced growth (final mass = 0.07
g) and survival (25%) compared to controls (0.37 g and 67%, respectively).
Accumulation of trace elements, as well as reductions in growth and survival,
were more pronounced than in previous laboratory studies, suggesting that
resource conditions may be important in mediating ash toxicity. Taken
together, our studies suggest that ash discharge into aquatic systems
is a more serious threat to the health of benthic fish than previously
predicted based upon laboratory toxicity tests.
Keywords: Coal combustion wastes; Microcosms; Mesocosms;
Selenium; Cadmium; Trophic transfer
SREL Reprint #2764
Hopkins, W. A., B. P. Staub, J. W. Snodgrass, B. E. Taylor, A. E. DeBiase, J. H. Roe, B. P. Jackson and J. D. Congdon. 2004. Responses of benthic fish exposed to contaminants in outdoor microcosms - examining the ecological relevance of previous laboratory toxicity tests. Aquatic Toxicology 68:1-12.
