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USGS1997

Cytochrome P450 and organochlorine contaminants in black-crowned night-herons from the Chesapeake Bay region, USA

Black-crowned night-heron ( Nycticorax nycticorax ) offspring were collected from a relatively uncontaminated coastal reference site (next to Chincoteague National Wildlife Refuge, VA, USA) and two sites in the Chesapeake Bay watershed (Baltimore Harbor, MD and Rock Creek Park, Washington, DC, USA). Hepatic microsomal activities of benzyloxyresorufin- O -dealkylase and ethoxyresorufin- O -dealkylase were significantly elevated (up to sixfold and ninefold induction, respectively) in pipping embryos from the Baltimore Harbor colony compared to the reference site, whereas values in embryos from the Rock Creek Park colony were intermediate. Concentrations of organochlorine pesticides and metabolites in pipping embryos from both sites in the Chesapeake watershed were greater than at the reference site but below the known threshold for reproductive impairment. However, concentrations of 10 arylhydrocarbon receptor-active polychlorinated biphenyl (PCB) congeners and estimated toxic equivalents were up to 37-fold greater in embryos collected from these two sites in the Chesapeake Bay region, with values for toxic congeners 77 and 126 exceeding those observed in pipping heron embryos from the Great Lakes. Monooxygenase activity of pipping embryos was associated with concentrations of several organochlorine pesticides, total PCBs, arylhydrocarbon receptor-active PCB congeners, and toxic equivalents ( r = 0.30–0.59), providing further evidence of the value of cytochrome P450 as a biomarker of organic contaminant exposure. Organochlorine contaminant levels were greater in 10-d-old nestlings from Baltimore Harbor than the reference site but had no apparent effect on monooxygenase activity or growth. These findings demonstrate induction of cytochrome P450 in pipping black-crowned night-heron embryos in the Chesapeake Bay region, probably by exposure to PCB congeners of local origin, and the accumulation of organochlorine pesticides and metabolites in nestling herons from Baltimore Harbor. Bio-monitoring with additional waterbird species (e.g., bald eagle, common tern, great blue heron) that appear to be more sensitive to PCBs than black-crowned night-herons is recommended to document health of waterbirds and remediation of the Chesapeake Bay.

Chesapeake Bay region↗

USGS1997

Trace-element accumulation by Hygrohypnum ochraceum in the upper Rio Grande Basin, Colorado and New Mexico, USA

Transplanted bryophytes can provide an indication of bioavailability. Rates of accumulation were related to the magnitude of ambient trace-element concentrations; maximal uptake occurred during the first 10 d of exposure. Trace-element concentrations in transplanted bryophytes could potentially be used to predict water and sediment concentrations that represent an integration of conditions over short to intermediate lengths of time, rather than instantaneous conditions as measured using water samples.

Environmental Toxicology and Chemistry↗

USGS1998

Overview of a workshop on screening methods for detecting potential (anti-) estrogenic/androgenic chemicals in wildlife

The U.S. Congress has passed legislation requiring the U.S. Environmental Protection Agency (U.S. EPA) to develop, validate, and implement screening tests for identifying potential endocrine-disrupting chemicals within 3 years. To aid in the identification of methods suitable for this purpose, the U.S. EPA, the Chemical Manufacturers Association, and the World Wildlife Fund sponsored several workshops, including the present one, which dealt with wildlife species. This workshop was convened with 30 international scientists representing multiple disciplines in March 1997 in Kansas City, Missouri, USA. Participants at the meeting identified methods in terms of their ability to indicate (anti-) estrogenic/androgenic effects, particularly in the context of developmental and reproductive processes. Data derived from structure-activity relationship models and in vitro test systems, although useful in certain contexts, cannot at present replace in vivo tests as the sole basis for screening. A consensus was reached that existing mammalian test methods (e.g., with rats or mice) generally are suitable as screens for assessing potential (anti-) estrogenic/ androgenic effects in mammalian wildlife. However, due to factors such as among-class variation in receptor structure and endocrine function, it is uncertain if these mammalian assays would be of broad utility as screens for other classes of vertebrate wildlife. Existing full and partial life-cycle tests with some avian and fish species could successfully identify chemicals causing endocrine disruption; however, these long-term tests are not suitable for routine screening. However, a number of short-term tests with species from these two classes exist that could serve as effective screening tools for chemicals inducing (anti-) estrogenic/androgenic effects. Existing methods suitable for identifying chemicals with these mechanisms of action in reptiles and amphibians are limited, but in the future, tests with species from these classes may prove highly effective as screens. In the case of invertebrate species, too little is known at present about the biological role of estrogens and androgens in reproduction and development to recommend specific assays.

Environmental Toxicology and Chemistry↗

USGS1998

Methylmercury chloride and selenomethionine interactions on health and reproduction in mallards

Adult mallards ( Anas platyrhynchos ) were fed a control diet or diets containing 10 ppm mercury as methylmercury chloride, 10 ppm selenium as seleno- DL -methionine, or 10 ppm mercury plus 10 ppm selenium. One of 12 adult males fed 10 ppm mercury died, and eight others suffered paralysis of the legs by the time the study was terminated. However, when the diet contained 10 ppm selenium in addition to the 10 ppm mercury, none of 12 males became sick. In contrast to the protective effect of selenium against mercury poisoning in males, selenium plus mercury was worse than selenium or mercury alone for some measurements of reproductive success. Both selenium and mercury lowered duckling production through reductions in hatching success and survival of ducklings, but the combination of mercury plus selenium was worse than either mercury or selenium alone. Controls produced an average of 7.6 young per female, females fed 10 ppm selenium produced an average of 2.8 young, females fed 10 ppm mercury produced 1.1 young, and females fed both mercury and selenium produced 0.2 young. Teratogenic effects also were worse for the combined mercury plus selenium treatment; deformities were recorded in 6.1% of the embryos of controls, 16.4% for those fed methylmercury chloride, 36.2% for those fed selenomethionine, and 73.4% for those fed methylmercury chloride and selenomethionine. The presence of methylmercury in the diet greatly enhanced the storage of selenium in tissues. The livers of males fed 10 ppm selenium contained a mean of 9.6 ppm selenium, whereas the livers of males fed 10 ppm selenium plus 10 ppm mercury contained a mean of 114 ppm selenium. However, selenium did not enhance the storage of mercury. The results show that mercury and selenium may be antagonistic to each other for adults and synergistic to young, even within the same experiment.

Environmental Toxicology and Chemistry↗

USGS1998

Effects of mercury and selenium on glutathione metabolism and oxidative stress in mallard ducks

Earlier studies have reported on the toxicity and related oxidative stress of different forms of Se, including seleno- D ,L-methionine, in mallards ( Anas platyrhynchos ). This study compares the effects of Se (seleno- D ,L-methionine) and Hg (methylmercury chloride) separately and in combination. Mallard drakes received one of the following diets: untreated feed (controls), or feed containing 10 ppm Se, 10 ppm Hg, or 10 ppm Se in combination with 10 ppm Hg. After 10 weeks, blood, liver, and brain samples were collected for biochemical assays. The following clinical and biochemical alterations occurred in response to Hg exposure: hematocrit and hemoglobin concentrations decreased; activities of the enzymes glutathione (GSH) peroxidase (plasma and liver), glutathione- S -transferase (liver), and glucose-6-phosphate dehydrogenase (G-6-PDH) (liver and brain) decreased; hepatic oxidized glutathione (GSSG) concentration increased relative to reduced glutathione (GSH); and lipid peroxidation in the brain was detected by increased thiobarbituric reactive substances (TBARS). Effects of Se alone included increased hepatic GSSG reductase activity and brain TBARS concentration. Selenium in combination with Hg partially or totally alleviated effects of Hg on GSH peroxidase, G-6-PDH, and GSSG. These findings are compared in relation to field observations for diving ducks and other aquatic birds. It is concluded that since both Hg and excess Se can affect thiol status, measurement of associated enzymes in conjunction with thiol status may be a useful bioindicator to discriminate between Hg and Se effects. The ability of Se to restore the activities of G-6-PDH, GSH peroxidase, and glutathione status involved in antioxidative defense mechanisms may be crucial to biological protection from the toxic effects of methylmercury.

Environmental Toxicology and Chemistry↗

USGS1998

Association of mercury and selenium with altered glutathione metabolism and oxidative stress in diving ducks from the San Francisco Bay region

Ault male greater scaup ( Aythya marila ), surf scoters ( Melanitta perspicillata ), and ruddy ducks ( Oxyurajamaicensis ) were collected from Suisun Bay and coastal Tomales Bay in the greater San Francisco Bay area to assess exposure to inorganic contaminants. Hepatic Se concentrations were highest in greater scaup (geometric mean = 67 ppm dry weight) and surf scoters (119 ppm) in Suisun Bay, whereas hepatic Hg was highest (19 ppm) in greater scaup and surf scoters from Tomales Bay. Hepatic Se and Hg were lower in ruddy ducks and did not differ between locations. Hepatic supernatants were assayed for enzymes related to glutathione metabolism and antioxidant activity, including glucose-6-phosphate dehydrogenase (G-6-PDH), glutathione peroxidase (GSH peroxidase), glutathione reductase (GSSG reductase), and glutathione- S -transferase (GSH transferase). Glutathione peroxidase activity was higher in surf scoters and ruddy ducks, and G-6-PDH was higher in greater scaup and surf scoters from Suisun Bay than Tomales Bay. Glutathione reductase (GSSG) was higher in SS from Suisun Bay. The ratio of oxidized glutathione (GSSG) to reduced glutathione (GSH) was greater in all species from Tomales Bay. The following significant relationships were found in one or more species with increasing hepatic Hg concentration: lower body, liver, and heart weights; decreased hepatic GSH concentration and G-6-PDH and GSH peroxidase activities; increased ratio of GSSG to GSH; and increased GSSG reductase activity. With increasing hepatic Se concentration, GSH peroxidase increased, but GSH decreased. It is concluded that measurement of associated enzymes in conjunction with thiol status may be a useful bioindicator to discriminate between Hg and Se effects. Concentrations of Hg and Se and the above variables affected have been associated with adverse effects on reproduction and neurological function in experimental studies with mallards.

Environmental Toxicology and Chemistry↗

USGS1998

An epizootic of common loons in coastal waters of North Carolina: Concentrations of elemental contaminants and results of necropsies

A 1993 die-off of common loons ( Gavia immer ) in the coastal waters of North Carolina was investigated with emphasis on comparing mercury, selenium, arsenic, and lead between birds from the epizootic and reference specimens. Die-off specimens were emaciated but contained no ingested foreign bodies and no lesions suggestive of infectious disease. Results of bacteriology, virology, parasitology, and botulism testing were unremarkable. The geometric mean concentrations (wet weight) of liver mercury (10.9 ppm), and arsenic (0.96 ppm) did not differ between specimens from the die-off and reference loons from the same area that died of other causes. The geometric mean liver selenium concentration of die-off specimens (10.4 ppm) was significantly higher than that of reference loons. Liver lead concentrations were < 0.20 ppm in all but one sample (5.83 ppm). The geometric mean mercury concentration in the primary remiges of die-off specimens (5.44 ppm dry weight) was significantly lower than in reference birds. Liver mercury significantly correlated with liver selenium on a molar concentration basis. We interpret the range of liver mercury concentrations in birds from the epizootic, similar liver mercury concentrations in reference loons, and higher mercury concentrations in reference loon feathers as evidence that factors other than mercury were primarily responsible for the emaciation diagnosed as the cause of mortality.

North Carolina↗

USGS1998

Validity of using semipermeable membrane devices for determining aqueous concentrations of freely dissolved PAHs

An in-depth review of the recent contribution to this journal by Gustafson and Dickhut [1] prompts us to share our concerns regarding some of their conclusions. The paper presents data comparing three techniques for determining aqueous concentrations of freely dissolved polycyclic aromatic hydrocarbons (PAHs) gas sparging, lipid-containing semipermeable membrane devices (SPMDs) of the U.S. Geological Survey (USGS) design, and filtration followed by sorption using XAD-2 resin. Space limitations force us to limit our comments to problems resulting from an apparent lack of understanding of how SPMDs function. Several recent publications [2–13] have described the theoretical and practical considerations of SPMD usage. Gustafson and Dickhut fail to cite any papers describing SPMDs published after 1992, even though some 18 papers have been published in American and European journals since then and several SPMD studies have been presented at many major meetings.

Environmental Toxicology and Chemistry↗

USGS1998

Comparative developmental toxicity of planar polychlorinated biphenyl congeners in chickens, American kestrels, and common terns

The effects of polychlorinated biphenyl (PCB) congeners, PCB 126 (3,3′,4,4′,5-pentaCB) and PCB 77 (3,3′4,4′-tetraCB), were examined in chicken ( Gallus gallus ), American kestrel ( Falco sparverius ), and common tern ( Sterna hirundo ) embryos through hatching, following air cell injections on day 4. PCB 126 caused malformations and edema in chickens starting at 0.3 ppb, in kestrels at 2.3 to 23 ppb, but in terns only at levels affecting hatching success (44 ppb). Extent of edema was most severe in chickens and least in terns. Defects of the beak were common in all species but with crossed beak most prevalent in terns. Effects on embryo growth were most apparent for PCB 126 in chickens and kestrels. The approximate 50% lethal dose (LD50) for PCB 126 in chickens was 0.4 ppb, in kestrels was 65 ppb, and in terns was 104 ppb. The approximate LD50 for PCB 77 in chickens was 2.6 ppb and in kestrels was 316 ppb. Induction of cytochrome P450 associated monooxygenase activity (ethoxyresorufin- O -dealkylase activity) by PCB 126 in chick embryo liver was about 800 times more responsive than in tern and at least 1,000 times more responsive than in kestrel. High concentrations of PCB 126 found in bald eagle eggs are nearly 20-fold higher than the lowest toxic concentration tested in kestrels. Concentrations of PCB 126 causing low-level toxic effects in common tern eggs are comparable to highest levels in common terns and Forster's terns in the field, suggesting additional involvement of other compounds in the Great Lakes.

Environmental Toxicology and Chemistry↗

USGS1998

Development and application of a marine sediment pore-water toxicity test using Ulva fasciata zoospores

An acute (96 h) pore-water toxicity test protocol using germination and growth of Ulva fasciata zoospores as endpoints was developed to test the toxicity of marine and estuarine sediment pore-water samples. Tests with an organic toxicant (sodium dodecyl sulfate; SDS), three metals (Cd, Cu, and Zn), and ammonia (NH 3 ) were conducted to determine zoospore sensitivity. Zoospore germination and gametophyte growth were as sensitive to SDS as sea urchin ( Arbacia punctulata ) fertilization and embryological development. Zoospore sensitivity to metals was greater than or comparable to that of adult macroalgae. Zoospores were less sensitive to NH 3 than were other commonly used toxicity test organisms. Test results using this algal assay with sediment pore-water samples with high NH 3 concentrations were compared with results from sea urchin fertilization and embryological development tests for the same samples. Ulva fasciata zoospore germination was not affected by samples with high NH 3 concentrations that were toxic in both sea urchin tests. Zoospore tolerance of NH 3 and sensitivity to other contaminants indicate that their response may be useful in toxicity identification evaluation studies with pore-water samples that contain high concentrations of unionized NH 3 .

Environmental Toxicology and Chemistry↗

USGS1998

Predicting the toxicity of sediment-associated trace metals with simultaneously extracted trace metal: Acid-volatile sulfide concentrations and dry weight-normalized concentrations: A critical comparison

The relative abilities of sediment concentrations of simultaneously extracted trace metal: acid-volatile sulfide (SEM: AVS) and dry weight-normalized trace metals to correctly predict both toxicity and nontoxicity were compared by analysis of 77 field-collected samples. Relative to the SEM:AVS concentrations, sediment guidelines based upon dry weight-normalized concentrations were equally or slightly more accurate in predicting both nontoxic and toxic results in laboratory tests.

Environmental Toxicology and Chemistry↗

USGS1998

Induction of cytochrome P450-associated monooxygenases in northern leopard frogs, Rana pipiens, by 3,3′,4,4′,5-Pentachlorobiphenyl

Northern leopard frogs ( Rana pipiens ) were injected intraperitoneally either with a solution of polychlorinated biphenyl (PCB) 126 in corn oil at a concentration of 0.2, 0.7, 2.3, or 7.8 mg/kg body weight or with corn oil alone. Appropriate assay conditions with hepatic microsomes were determined for four cytochrome P450-associated monooxygenases: ethoxyresorufin- O -dealkylase (EROD), methoxy-ROD (MROD), benzyloxy-ROD (BROD), and pentoxy-ROD (PROD). One week after PCB administration, the specific activities of EROD, MROD, BROD, and PROD were not elevated at doses ≤0.7 mg/kg ( p > 0.05) but were significantly increased at doses ≥2.3 mg/kg compared to the control groups ( p < 0.05). The increased activities of these four enzymes were 3 to 6.4 times those in the control groups. The increased activities were maintained for at least 4 weeks. Because of a lack of induction at low doses of PCB 126, which were still relatively high compared to currently known environmental concentrations, we suspect that EROD, MROD, BROD, and PROD activities are not sensitive biomarkers for coplanar PCB exposure in leopard frogs.

Environmental Toxicology and Chemistry↗

USGS1998

Reproduction and environmental contamination in tree swallows nesting in the Fox River drainage and Green Bay, Wisconsin, USA

Concentration, accumulation, and effects of polychlorinated biphenyls (PCBs) o nreproduction in tree swallows ( Tachycineta bicolor ) were studied at four sites in the Fox River drainage and in Green Bay, Lake Michigan, Wisconsin, USA, in 1994 and 1995. Total PCBs in eggs and newly hatched young (mean = 3.01 μg/g wet weight, years and sites combined) and 12-d-old nestlings (mean = 2.34 μg/g wet weight) at two contaminated sites (Kidney Island and Arrowhead) were higher than concentrations at two reference sites (Lake Poygan and High Cliff State Park, years and sites combined, pippers mean = 0.26 μg/g, nestlings mean = 0.01 μg/g). Concentrations of 11 PCB congeners were also higher at contaminated compared to reference sites. Polychlorinated biphenyls (PCBs) accumulated in nestlings at a higher rate (1.34–6.69 μg/d) at contaminated sites compared to reference locations (0.06–0.42 μg/d). Dichlorodiphenyldichloroethylene (DDE) was the only other organochlorine found in all samples; concentrations for all samples averaged ≤0.20 μg/g wet weight. Total PCBs and p,p ′-DDE concentrations did not differ among clutches where all eggs hatched, some eggs hatched, and no eggs hatched.

Wisconsin↗

USGS1998

Effects of 3,3′,4,4′,5-pentachlorobiphenyl and 2,3,7,8-tetrachlorodibenzo-p-dioxin injected into the yolks of double-crested cormorant (Phalacrocorax auritus) eggs prior to incubation

Double-crested cormorant ( Phalacrocorax auritus ) eggs were injected with either 3,3′,4,4′,5-pentachlorobiphenyl (polychlorinated biphenyl [PCB] 126; 70-698 μg/kg egg) or 2,3,7,8-tetrachlorodibenzo- p -dioxin (TCDD; 1.3-11.7 μg/kg egg) prior to incubation. These compounds were injected into the yolks of cormorant eggs collected from incomplete clutches at isolated colonies on Lake Winnipegosis, Manitoba, Canada. Eggs were incubated for approximately 26 to 28 d. After hatching the brain, bursa, heart, liver, and spleen were dissected and weighed. Torsos were preserved in formalin for examination of the gonads. Median lethal doses (LD50s) calculated from mortality data at hatching were 177 and 4.0 μg/kg egg for PCB 126 and TCDD, respectively. No significant differences were found in the incidence of developmental abnormalities in any of the treatment groups. Bursa weights were significantly less in the greatest (11.7 μg/kg egg) TCDD group compared to the vehicle control group. Spleen weights were significantly less in the 349 μg PCB 126/kg egg and the 5.4 and 11.7 μg TCDD/kg egg groups when compared to the vehicle control group. No histological alterations of the gonads were found. Hepatic ethoxyresorufin- O -deethylase activity in all PCB 126 and TCDD dose groups was significantly greater compared to the control activity. The toxic equivalency factor for PCB 126 was 0.02.

Environmental Toxicology and Chemistry↗

USGS1998

Relation of lead exposure to sediment ingestion in mute swans on the Chesapeake Bay, USA

Although wildlife risk assessments are generally based on the accumulation of environmental contaminants through food chains, wildlife may also ingest contaminants incidentally with sediment. Forty-two mute swans ( Cygnus olor ) were collected from unpolluted portions of central Chesapeake Bay, Maryland, USA, in spring 1995, and their intestinal digesta were analyzed for 13 metals (aluminum [Al], boron, barium, cadmium, copper [Cu], iron, magnesium, manganese, nickel, lead [Pb], strontium, vanadium, and zinc) and for acid-insoluble ash, a marker of sediment. Swan livers and sediment samples also were analyzed for the same metals. Group method of data handling demonstrated that the digesta Al, which is associated with clays, was the best predictor of digesta Pb. Adding concentrations of other metals as predictors did not improve the accuracy of the estimates of Pb concentrations from Al concentrations. The r 2 of the equation relating the log of digesta Pb to the log of digesta Al was 0.86, whereas the r 2 of the equation relating the log of digesta Pb to the log of digesta acid-insoluble ash was 0.50. Accounting for the sediment ingested was critical to determining the exposure of mute swans to Pb, as well as to some of the other metals, and sediment ingestion should be considered in ecotoxicological risk assessments of waterfowl. The mean of 7.4% acid-insoluble ash in the digesta corresponded to an estimated 3.2% sediment in the diet. The Pb concentrations in the digesta were two to three times the concentration that would have been predicted from sediment Pb concentrations; presumably, the swans had ingested clays high in Pb that had settled on the vegetation. The swans were probably not exposed to high Cu concentrations but nevertheless had hepatic Cu concentrations that would be considered very high if found in other species.

Environmental Toxicology and Chemistry↗

USGS1998

Blood changes in mallards exposed to white phosphorus

White phosphorus (P 4 ) has been extensively used by the military for various purposes, including marking artillery impacts and as an obscurant. Target practice in an Alaskan tidal marsh during the last 4 decades has deposited large amounts of P 4 particles in sediments and water, which have resulted in die-offs of several waterfowl species. Because the toxicity of P 4 in birds has not been well documented and because it is quickly excreted or metabolized in living animals, we sought to determine the effects of experimental dosing on blood characteristics in game farm mallards ( Anas platyrhynchos ). In two experiments, one employing single doses of 5.4 mg P 4 per kilogram body weight in corn oil and the other using daily repeated doses of pelletized P 4 at either 0.5 or 1.0 mg/kg, there were significant changes in aspartate aminotransferase, alanine aminotransferase, lactate dehydrogenase (LDH), inorganic P, hematocrit, and hemoglobin. Other indications of exposure included changes in uric acid, creatinine, and total protein, which were consistent with reported liver and kidney damage due to this contaminant. Changes in white blood cells included a greater frequency of thrombocytes and fewer lymphocytes in dosed birds compared to controls. A biomarker of exposure based on LDH activity and hemoglobin is proposed.

Environmental Toxicology and Chemistry↗

USGS1998

Photoenhanced toxicity of a carbamate insecticide to early life stage anuran amphibians

Aican clawed frog ( Xenopus laevis ) and gray tree frog ( Hyla versicolor ) embryos and tadpoles were exposed to sublethal levels of carbaryl, a broad-spectrum insecticide, and ultraviolet radiation to determine interactive and sublethal effects. Ultraviolet intensity (UV-B [285–320 nm] plus UV-A [321–400 nm]) was controlled with various types of plastic filters and quantified with a scanning spectroradiometer. Significant differences in swimming activity and mortality of both species were evident during the 96-h experiments. Ultraviolet-B radiation alone and carbaryl in the presence of UV-B significantly decreased swimming activity of both species. As little as 1.5% intensity of ambient solar UV-B radiation photoactivated carbaryl. Toxicity of 7.5 mg/L carbaryl increased by 10-fold in the presence of UV-B in all species and life stages tested. Our results indicate that photoenhancement by solar UV-B radiation should be considered when evaluating the toxicity of contaminants to amphibians and other organisms.

Environmental Toxicology and Chemistry↗

USGS1999

Tolerance of freshwater test organisms to formulated sediments for use as control materials in whole-sediment toxicity tests

A method is described for preparing formulated sediments for use intoxicity testing. Ingredients used to prepare formulated sediments included commercially available silt, clay, sand, humic acid, dolomite, and α-cellulose (as a source of organic carbon). α-Cellulose was selected as the source of organic carbon because it is commercially available, consistent from batch to batch, and low in contaminant concentrations. The tolerance of freshwater test organisms to formulated sediments for use as control materials in whole-sediment toxicity testing was evaluated. Sediment exposures were conducted for 10 d with the amphipod Hyalella azteca , the midges Chironomus riparius and C. tentans , and the oligochaete Lumbriculus variegatus and for 28 d with H. azteca . Responses of organisms in formulated sediments was compared with a field-collected control sediment that has routinely been used to determine test acceptability. Tolerance of organisms to formulated sediments was evaluated by determining responses to varying levels of α-cellulose, to varying levels of grain size, to evaluation of different food types, or to evaluation of different sources of overlying water. In the 10-d exposures, survival of organisms exposed to the formulated sediments routinely met or exceeded the responses of test organisms exposed to the control sediment and routinely met test acceptability criteria required in standard methods. Growth of amphipods and oligochaetes in 10-d exposures with formulated sediment was often less than growth of organisms in the field-collected control sediment. Additional research is needed, using the method employed to prepare formulated sediment, to determine if conditioning formulated sediments before starting 10-d tests would improve the growth of amphipods. In the 28-d exposures, survival of H. azteca was low when reconstituted water was used as the source of overlying water. However, when well water was used as the source of overlying water in 28-d exposures, consistent responses of amphipods were observed in both formulated and control sediments.

Environmental Toxicology and Chemistry↗