Amphipod Survival Research Articles

EROD activity in fish as an independent measure of contaminant-induced mortality of invertebrates in sediment bioassays

The survival of amphipods in sediment bioassays was compared to the induction of ethoxyresorufin-O-deethylase (EROD) activity in speckled sanddabs ( Citharichthys stigmaeus) to investigate the relative importance of physical and chemical characteristics of sediment in toxicity bioassays. Sediments from San Francisco Bay containing 1–30 ppm (dry) of polynuclear aromatic hydrocarbons (PAHs), 3–20 ppb (dry) of polychlorinated biphenyls (PCBs) and variable concentrations of several trace elements were used in separate exposure assays for sanddabs (60 d) and the amphipod Eohaustorius estuarius (10 d). A highly significant correlation ( r 2 = 0.90, p <. 001) was documented between EROD activity in the sanddabs and Eohaustorius survival for all treatments. The accurate prediction of amphipod survival by the contaminant exposure biomarker in the fish is consistent with the contention that contamination, rather than physical characteristics of the sediments, is the cause of amphipod mortality. This result supports the use of these bioassays to screen sediments for ecologically significant contaminant concentrations.

A laboratory‐formulated sediment incorporating synthetic acid‐volatile sulfide

AbstractThe application of laboratory‐formulated sediment (LFS) could be expanded if toxicologically significant characteristics of sediment other than particle‐size distribution, organic carbon content, and pH could be manipulated. This report describes the preparation of a LFS containing synthetic acid‐volatile sulfide (AVS) and shows its similarity to natural sediment AVS. Several formulations were evaluated with respect to toxicity to Hyalella azteca and chemical stability. Amphipod survival was highest (95%) in LFS formulations in which the molar iron(II)/sulfide ratio was near 1, although amphipod survival was &gt;l80% in six of seven formulations with ≤20% excess metal or sulfide. Synthetic AVS in the test system oxidized rapidly at the sediment surface, but AVS at depth was stable for &gt;30 d when isolated from air or aerated water. Oxidation‐reduction potential measurements and AVS analysis of core slices revealed a vertical oxidation profile, apparently established and limited by oxygen diffusion. A formulation consisting of a 1:1 molar ratio of iron and sulfide (FeS) was evaluated with respect to complexation of copper, zinc, and nickel and to the corresponding reduction in toxicity using W‐AH. azteca toxicity tests. Amphipod mortality in metal‐spiked LFS with metal/AVS molar ratios &gt;1 was high relative to controls. In contrast, amphipod survival in metal‐spiked LFS with metal/AVS molar ratios &gt;1 was generally similar to amphipod survival in nonspiked LFS containing synthetic AVS. A few exceptions, where toxicity was noted when metal/AVS ratios were &lt;1, could be explained by high concentrations of dissolved iron, which was released by the metal + AVS displacement reaction. The LFS containing synthetic AVS appears to mimic natural sediment AVS and thus can provide consistent and controlled substrates suitable for investigating metal/sediment chemistry and toxicity and for developing realistic sediment quality criteria for metals.

Watercress Allelochemical Defends High‐Nitrogen Foliage Against Consumption: Effects on Freshwater Invertebrate Herbivores

Watercress (Nasturtium officinale) is a spring—stream macrophyte that possesses glucosinolates, which are hydrolyzed to feeding deterrent isothiocyanates when the enzyme myrosinase is released by tissue damage. Previous studies indicated that frequently associated aquatic shredders strongly prefer yellowed—senescent leaves over fresh—green foliage, because the latter releases much more isothiocyanate than senescent watercress. When the action of myrosinase was blocked by heating the tissue, the shredders' preference shifted to heated—green tissue, which contains much more nitrogen than that found in senescent tissue. Here we report a series of no—choice experiments on various tissue types designed to determine intermediate and long—term consumption rates and associated impacts on growth and survival of shredders associated with watercress. The amphipod Gammarus pseudolimnaeus, the caddisflies Pycnopsyche sp., Hesperophylax designatus, and Limnephilus sp., and the snail Physella gyrina, all consumed much more senescent than fresh—green tissue. In long—term tests with G. pseudolimnaeus, H. designatus, and Limnephilus sp., growth was negative or zero on the defended fresh—green tissue and often highest on heated—green tissue. Reaction to glucosinolates differed among shredders. For the caddisflies, growth and survival were positively correlated with bulk tissue and nitrogen consumption, which were highest for heated—green tissue. However, amphipod survival was significantly lowered on heated—green watercress, although it was readily consumed. Therefore, consumption of high—glucosinolate tissue was detrimental to the amphipods but not to caddisflies. Our results indicate that the glucosinolate—myrosinase system defends live green watercress against herbivory by an array of aquatic invertebrates. These generalist herbivores forgo eating high—quality fresh—green leaves because of plant defenses and instead settle for lower quality senescent leaves. When the defense system was experimentally shut down, these herbivores readily consumed young green tissue and frequently showed higher growth rates than those achieved on the senescent, but undefended, leaves they typically consume. Evidently, these shredders face a trade—off of high nitrogen and high defense vs. low nitrogen and low defense.

Estimates of the Spatial Extent of Sediment Toxicity in Major U.S. Estuaries

Acute laboratory toxicity tests were performed on surficial sediments collected from 1176 locations throughout 22 estuarine areas in the United States. Toxicity was determined with three standardized procedures : 10-day amphipod survival tests with solid-phase (bulk) sediments ; 5-min microbial bioluminescence tests with organic solvent extracts of the sediments ; and either 1-h sea urchin fertilization tests or 48-h mollusc embryo tests with the porewater of the sediments. Test results were weighted to the sizes (km 2 ) of the geographic strata in which samples were collected. Selected bays and estuaries were sampled along the Atlantic and Gulf of Mexico coasts and in southern California along the Pacific coast of the United States. The individual survey areas ranged in size from <1.0 km 2 to over 550 km 2 . Collectively, approximately 2532 km 2 were sampled in the 22 surveys. Toxicity was observed in the amphipod survival tests of bulk sediments in approximately 10.9% of the combined area. These data suggest that acute toxicity as measured with adult crustaceans was restricted to small portions of these urbanized estuaries, principally maritime harbors and industrialized bayous and waterways. Toxicity was much more pervasive in the tests of solvent extracts and 100% porewater, indicating that approximately 61% and 43%, respectively, ofthe combined areas sampled were toxic. The spatial extent of toxicity decreased to 11% and 5% in tests of 50% and 25% porewater, respectively. In most areas each test indicated different patterns in toxicity, and consequently, the concordance in estimates oftoxicity among different tests was very small. Estimates of the spatial extent of toxicity probably would differ if tests were performed elsewhere and/or with different organisms.

Measuring bioavailable copper using anodic stripping voltammetry

AbstractSince speciation can affect bioavailability and toxicity of copper in aquatic systems, accurate predictions of effects of bioavailable forms require detection and/or measurement of these forms. To develop an approach for measurement of bioavailable copper, a copper sulfate solution (CuSO4·3Cu(OH)2·H2O) was used in 10‐d aqueous and sediment toxicity tests with Hyalella azteca Saussure. These tests encompassed ranges of pH (6.5 to 8.1), alkalinity (10 to 70 mg/L as CaCO3), hardness (10 to 70 mg/L as CaCO3), and conductivity (30 to 300 μmho/cm). Changes in copper speciation were measured using atomic absorption spectroscopy (AA) for dissolved copper and differential pulse anodic stripping voltammetry (DPASV) for labile copper, and concentrations were evaluated relative to amphipod survival. Ten‐day LC50s based on AA‐measured aqueous copper concentrations ranged from 42 to 142 μg Cu/L, and LC50s based on DPASV‐measured copper concentrations ranged from 17.4 to 24.8 μg Cu/L. In 10‐d tests using copper‐amended sediments with diverse characteristics and AA‐measured copper concentrations spanning an order of magnitude, total copper concentrations were not predictive of sediment toxicity, but H. azteca survival was explained by DPASV measurements that varied by ≤4%. In order to make defensible estimates of the potential risk of metals in sediments or water, it is essential to identify the fraction of total metal that is bioavailable. In these experiments, DPASV was useful for measuring bioavailable copper in aqueous and sediment tests with H. azteca.

Sediment quality assessment studies of Tampa bay, Florida

AbstractA survey of the toxicity of sediments throughout the Tampa Bay estuary was performed as part of the National Oceanic and Atmospheric Administration's National Status and Trends Program. The objectives of the survey were to determine the spatial extent and severity of toxicity and to identify relationships between chemical contamination and toxicity. Three independent toxicity tests were performed: a 10‐d amphipod survival test of the whole sediments with Ampelisca abdita, a sea urchin fertilization test of sediment pore water with Arbacia punctulata, and a 5‐min Microtox® bioluminescence test with solvent extracts of the sediments. Seventy‐three percent of the 165 undiluted sediment pore‐water samples were significantly toxic relative to reference samples with the sea urchin fertilization test. In contrast, only 2% of the 165 samples were significantly toxic in the amphipod tests. The causes of toxicity were not determined. However, concentrations of numerous trace metals, pesticides, polychlorinated biphenyl (PCB) congeners, polycyclic aromatic hydrocarbons (PAHs), and ammonia were highly correlated with pore‐water toxicity. Concentrations of many substances, especially total dichlorodiphenyltrichloroethanes (DDTs), endrin, total PCBs, certain PAHs, lead, and zinc, occurred at concentrations in the toxic samples that equaled or exceeded concentrations that have been previously associated with sediment toxicity.

Relative sensitivity of five benthic invertebrate species to reference toxicants and resin‐acid contaminated sediments

AbstractFive sediment‐dwelling native New Zealand freshwater invertebrate species (amphipod, Chaetocorophium c.f. lucasi; clam, Sphaerium novaezelandiae; oligochaete, Lumbriculus variegatus; tanaid, Tanais standfordi; and the burrowing mayfly, Ichthybotus hudsoni) were assessed for their suitability for sediment toxicity testing by comparison of sensitivity to reference toxicants [phenol and pentachlorophenol (PCP)] and contaminated sediments. The 96‐h EC50 values at 20°C showed a greater range in test sensitivity for phenol (30‐fold range) from the most sensitive test, amphipod (8.1 mg/L), to the least sensitive one, clam (243 mg/L), compared with PCP (14‐fold range), with amphipod the most sensitive test species (0.13 mg/L) and tanaid the least sensitive (1.8 mg/L). Clam reburial was a more sensitive end point than was lethality for phenol (by 20‐fold) and PCP (by 2.4‐fold). Four of the test species, excluding the tanaid, showed good 10‐d survival in reference muds (≥87%) but lower survival in sand sediments (≥79%). Bleached kraft mill sediment containing high resin‐acid concentrations (total 1,900 mg/kg dry weight) showed significant reductions in amphipod survival (15%), clam reburial (30%), and oligochaete survival (17%), and reproduction (49%). Amphipods, clams, and oligochaetes were the most promising species for sublethal test development.

Effects of storage time on toxicity of sediments from puget sound, Washington

AbstractThe effects of sediment storage time were determined for three sediment toxicity tests: the amphipod test using Rhepoxynius abronius, the polychaete test using Neanthes sp., and the Microtoxr̀ test using Photobacterium phosphoreum. Sediments were collected from a reference area and a contaminated area in Puget Sound to determine the effects of storage time on each type of sediment. Toxicity comparisons were also made between the two kinds of sediment to simulate the manner in which the data might be analyzed in a regulatory or decision‐making context. Sediments were stored at 4°C for as long as 16 weeks. Results of all three toxicity tests varied significantly with storage time for each type of sediment. Amphipod survival generally decreased with storage time, whereas luminescence in the Microtox test and polychaete biomass varied unpredictably. The significance of differences between results for the two sediments varied unpredictably with storage time for the amphipod and Microtox tests. By contrast, differences were consistently significant for all storage times for the polychaete test, primarily because of the large differences in the test response between sediments. These results suggest that effects of storage time are greater for results indicative of low to intermediate levels of toxicity than for results indicative of high levels of toxicity. It is recommended that sediments be tested as soon as possible after field collection to minimize the potential for alterations of toxicity during storage.

Growth of an amphipod and a bivalve in uncontaminated sediments: Implications for chronic toxicity assessments

This study assessed the sensitivity of the amphipod Chaetocorophium cf. lucasi, an inhabitant of New Zealand estuarine muddy sediments, and of the bivalve Macomona liliana, commonly found in New Zealand sandflats, to sediment particle-size distribution, total organic carbon, total organic nitrogen and water content. Growth and survival were evaluated after different test exposure times using laboratory-prepared natural sediment mixtures of sand and mud. The results suggest that amphipod survival was affected by the type of sand more than by the concentration of sand in the sediment samples. In samples with high survival rates, amphipod growth was impaired in sediments with higher sand proportions after a 10-day exposure, but after longer periods (28 or 30 days) there were no significant differences among treatments which had ≤76% sand. Bivalve survival and growth were not significantly affected by different natural sediment characteristics. Test duration for chronic toxicity tests with the bivalve M. liliana and the amphipod C. cf. lucasi should be at least 28 days for the detection of significant growth relative to the initial size.

RELATIVE SENSITIVITY OF FIVE BENTHIC INVERTEBRATE SPECIES TO REFERENCE TOXICANTS AND RESIN-ACID CONTAMINATED SEDIMENTS

Five sediment-dwelling native New Zealand freshwater invertebrate species (amphipod, Chaetocorophium c.f. lucasi; clam, Sphaerium novaezelandiae; oligochaete, Lumbriculus variegatus; tanaid, Tanais standfordi; and the burrowing mayfly, Ichthybotus hudsoni) were assessed for their suitability for sediment toxicity testing by comparison of sensitivity to reference toxicants [phenol and pentachlorophenol (PCP)] and contaminated sediments. The 96-h EC50 values at 20°C showed a greater range in test sensitivity for phenol (30-fold range) from the most sensitive test, amphipod (8.1 mg/L), to the least sensitive one, clam (243 mg/L), compared with PCP (14-fold range), with amphipod the most sensitive test species (0.13 mg/L) and tanaid the least sensitive (1.8 mg/L). Clam reburial was a more sensitive end point than was lethality for phenol (by 20-fold) and PCP (by 2.4-fold). Four of the test species, excluding the tanaid, showed good 10-d survival in reference muds (≥87%) but lower survival in sand sediments (≥79%). Bleached kraft mill sediment containing high resin-acid concentrations (total 1,900 mg/kg dry weight) showed significant reductions in amphipod survival (15%), clam reburial (30%), and oligochaete survival (17%), and reproduction (49%). Amphipods, clams, and oligochaetes were the most promising species for sublethal test development.

EFFECTS OF STORAGE TIME ON TOXICITY OF SEDIMENTS FROM PUGET SOUND, WASHINGTON

The effects of sediment storage time were determined for three sediment toxicity tests: the amphipod test using Rhepoxynius abronius, the polychaete test using Neanthes sp., and the Microtoxr̀ test using Photobacterium phosphoreum. Sediments were collected from a reference area and a contaminated area in Puget Sound to determine the effects of storage time on each type of sediment. Toxicity comparisons were also made between the two kinds of sediment to simulate the manner in which the data might be analyzed in a regulatory or decision-making context. Sediments were stored at 4°C for as long as 16 weeks. Results of all three toxicity tests varied significantly with storage time for each type of sediment. Amphipod survival generally decreased with storage time, whereas luminescence in the Microtox test and polychaete biomass varied unpredictably. The significance of differences between results for the two sediments varied unpredictably with storage time for the amphipod and Microtox tests. By contrast, differences were consistently significant for all storage times for the polychaete test, primarily because of the large differences in the test response between sediments. These results suggest that effects of storage time are greater for results indicative of low to intermediate levels of toxicity than for results indicative of high levels of toxicity. It is recommended that sediments be tested as soon as possible after field collection to minimize the potential for alterations of toxicity during storage.

Herbivore Resistance to Seaweed Chemical Defense: The Roles of Mobility and Predation Risk

Numerous small sedentary herbivores (mesograzers such as amphipods, small crabs, and gastropods) are resistant to seaweed secondary metabolites that deter larger, more mobile herbivorous fishes. In addition, specialist mesograzers experience reduced predation from fishes when living on seaweeds that produce these compounds. In this study we tested the hypothesis that generalist, as opposed to specialist, mesograzers can also benefit from reduced predation when they occupy chemically defended plants. Secondly, we assessed the hypothesis that low herbivore mobility, unconfounded by herbivore size or specialized feeding, selects for tolerance of seaweed chemical defenses, by comparing responses to the chemically defended brown seaweed Dictyota menstrualis of three sympatric, generalist amphipods that differ in mobility (Ampithoe longimana, Ampithoe valida, and Gammarus mucronatus). Response to Dictyota's chemical defenses varied as much among these three amphipods as among the phylogenetically distant fishes and mesograzers studied previously and supported the hypothesis that less mobile herbivores should be most tolerant of plant chemical defenses. In laboratory experiments, A. longimana moved little, preferentially consumed Dictyota over other seaweeds, and was unaffected by all Dictyota secondary metabolites tested. In contrast, G. mucronatus was active, it did not feed on Dictyota, and two of three Dictyota secondary metabolites deterred its grazing. Distribution of amphipods in the field suggested that these feeding patterns affected amphipod risk of predation. A. longimana reached its highest abundance on Dictyota, which is unpalatable to omnivorous fish predators, during the season when fish are most abundant. At the same time, the highly active G. mucronatus decreased to near extinction. Like G. mucronatus, A. valida was detterred by two Dictyota secondary metabolites, did not eat Dictyota, and disappeared when fishes were abundant. Experiments confirmed that A. longimana was less vulnerable to fish predation when occupying a chemically defended seaweed than when occupying a palatable seaweed. This decreased predation resulted primarily from a decreased frequency of encounter with predators when amphipods were on chemically defended plants. When we experimentally equalized encounter rates between omnivorous pinfish (Lagodon rhomboides) and the seaweed Dictyota menstrualis and Ulva curvata (unpalatable and palatable, respectively, to pinfish) in the laboratory, amphipods occupying these two plants were eaten at similar rates. In contrast, when live amphipods were affixed to Ulva and Dictyota and deployed in the field, amphipods survived only on Dictyota. Heavy fish grazing on Ulva in the latter experiment suggests that poor survival of amphipods on Ulva may have resulted from greater detection and/or incidental ingestion of amphipods on this plant, due to frequent visitation by fishes. Infrequent visitation of Dictyota by foraging fish also may explain A. longimana's persistence through the summer on this chemically defended seaweed while the two Ulva—associated amphipods declined precipitously. These results (1) confirm that association with chemically defended plants can reduce predation on generalist, as well as specialist, herbivores and (2) suggest that preferential feeding on chemically defended plants is most likely for sedentary mesograzers because low mobility enhances the ability to exploit chemically defended seaweeds as refuges from fish predation.

Sediment Studies Provide Key Information on the Need to Treat Sewage Discharged to Sea by a Major Canadian City

Relatively untreated (screened) municipal wastes from the City of Victoria, B.C. and environs are discharged to the sea as effluent from two long outfall pipes, only one of which (Macaulay Point) discharges to a depositional zone. Sediments along transects away from the Macaulay Point outfall were collected and the following parameters determined: contamination (selected chemicals of concern), toxicity (polychaete survival and growth, amphipod survival, and bivalve larvae abnormalities), and benthic infaunal community structure. Significant sediment contamination was restricted to within 100-400 m of the outfall with the exception of high PAH contamination due to the shipwreck of a collier in 1891. Sediment toxicity was restricted to effects on growth and development, also within 100-400 m of the outfall; survival was near control levels even at the outfall terminus. Benthic infaunal community structure indicated “moderate pollution” within 100 m of the outfall and showed a classic organic enrichment pattern of increasing species richness and lower abundance with distance from the outfall. Overall, the impact of the outfall on the sediments is minimal, highly restricted in extent, and not of major environmental concern. A public referendum, conducted after the release of this and of other scientific studies, resulted in the deferral of primary effluent treatment.

Evaluation of a laboratory‐generated NOEC for linear alkylbenzene sulfonate in outdoor experimental streams

AbstractLaboratory and field studies were conducted with linear alkylbenzene sulfonate (LAS) to evaluate the use of laboratory‐generated NOECs for protecting aquatic organisms in outdoor experimental streams. Fathead minnows (Pimephales promelas) and freshwater amphipods (Hyalella azteca) were exposed in the laboratory to an environmentally realistic mixture of LAS (average chain length C11 9) for 7 d; fathead minnows were also exposed in a 28‐d study. Calculated NOEC values based on survival and growth ranged from 0.3 to 0.9 mg/L for fathead minnows and from 0.6 to 1.4 mg/L for amphipods. Toxicity of LAS in 4‐, 7‐, and 28‐d exposures of fathead minnows was similar because mortality occurred within the initial 24 h of exposure; mortality was more sensitive than growth as a chronic end point. The addition of 5% sewage effluent to well and stream water had little effect on the bioavailability of LAS; however, total organic carbon levels were low (&lt;3 mg/L) in all treatments. A 45‐d exposure of three outdoor experimental streams to 0.36 mg/L LAS had no effects on survival of fathead minnows or amphipods, dynamics of benthic invertebrates, growth of periphyton, or processing of detrital leaves. Results indicated that the laboratory‐generated NOEC for LAS was protective of experimental stream communities under the studied conditions.

EVALUATION OF A LABORATORY-GENERATED NOEC FOR LINEAR ALKYLBENZENE SULFONATE IN OUTDOOR EXPERIMENTAL STREAMS

Laboratory and field studies were conducted with linear alkylbenzene sulfonate (LAS) to evaluate the use of laboratory-generated NOECs for protecting aquatic organisms in outdoor experimental streams. Fathead minnows (Pimephales promelas) and freshwater amphipods (Hyalella azteca) were exposed in the laboratory to an environmentally realistic mixture of LAS (average chain length C11 9) for 7 d; fathead minnows were also exposed in a 28-d study. Calculated NOEC values based on survival and growth ranged from 0.3 to 0.9 mg/L for fathead minnows and from 0.6 to 1.4 mg/L for amphipods. Toxicity of LAS in 4-, 7-, and 28-d exposures of fathead minnows was similar because mortality occurred within the initial 24 h of exposure; mortality was more sensitive than growth as a chronic end point. The addition of 5% sewage effluent to well and stream water had little effect on the bioavailability of LAS; however, total organic carbon levels were low (<3 mg/L) in all treatments. A 45-d exposure of three outdoor experimental streams to 0.36 mg/L LAS had no effects on survival of fathead minnows or amphipods, dynamics of benthic invertebrates, growth of periphyton, or processing of detrital leaves. Results indicated that the laboratory-generated NOEC for LAS was protective of experimental stream communities under the studied conditions.

Testing sediment toxicity in chesapeake bay with the amphipod Leptocheirus plumulosus: An evaluation

AbstractOrganisms selected for testing the toxicity of estuarine sediments must exhibit sensitivity to toxicants while remaining tolerant of wide ranges of salinities and sediment characteristics. The amphipod Leptocheirus plumulosus Shoemaker is an ecologically important infaunal inhabitant of Chesapeake Bay sediments. Leptocheirus plumulosus was exposed to a range of salinities and sediments varying in physical composition for up to 28 d in separate experiments to determine effects of natural environmental variables on amphipod survival and reproduction. No significant differences in adult survival were observed among salinity treatments ranging from 1.5 to 32 ppt or among sediment treatments varying in particle size and organic content. Significant effects on reproductive end points were detected, indicating the potential for incorporating sublethal end points into the bioassay. Acute 96‐h LC50 values for aqueous cadmium at a salinity of 6 ppt were determined for Leptocheirus plumulosus and the amphipod Hyalella azteca Saussure, an organism commonly used in freshwater sediment toxicity tests. The LC50 values were 0.30 mg Cd per liter and 0.19 mg Cd per liter for Leptocheirus plumulosus and Hyalella azteca, respectively.

Short‐ and long‐term sediment toxicity test methods with the amphipod Grandidierella japonica

AbstractMethods are described for conducting flow‐through sediment toxicity tests with the marine amphipod Grandidierella japonica. Short‐term (10‐d) exposures were conducted at 15°C in 1‐liter beakers containing a 2‐cm layer of sediment and 700 ml overlying seawater. Long‐term (28‐d) tests were conducted in 1‐liter beakers at 19°C with the weekly addition of food to the test chambers. Both methods were used to measure the toxicity of sediments from five locations in southern California. These sites included highly contaminated areas adjacent to large municipal wastewater outfalls and within industrialized harbors.Both test methods were sensitive to levels of contamination found in the field, but produced different patterns of effects. Short‐term mortality was greatest in amphipods exposed to the harbor sediments, while long‐term exposure produced the greatest reductions in survival and growth at the Los Angeles County Outfall site. Amphipod survival was unaffected by variations in sediment grain size, while this characteristic appeared to have an important effect on growth.

Effects of natural sediment features on survival of the phoxocephalid amphipod, Rhepoxynius abronius

Effects of sediment particle size and water content on the survival of the amphipod, Rhepoxynius abronius, were examined by manipulating these natural sediment features within static laboratory microcosms. Mean amphipod survival in fine, uncontaminated, field sediments (≥ 80% silt-clay) can be 15% lower than survival in native sediment. Storage of sediments at 4°C over 7–14 days did not change sediment toxicity, but handling (i.e. elutriation and recombination) of muddy sediments increased toxicity. Sediment particle size and organic content had greater impact on the survival of R. abronius than did sediment water content in modifying amphipod survival, but we could not independently separate the effects of these two sediment variables. A new set of criteria is proposed to interpret toxicity results from the amphipod bioassay in the light of the mortality associated with fine sediment particle size. The efficacy of these criteria to separate mortality caused by fine particles and chemical contaminants was tested by analyzing field survey data from 78 Puget Sound (WA) Urban sites. Using our new criteria, the toxicity of these sediments was found to closely reflect the degree of chemical contamination. We propose that an approach similar to this be undertaken for toxicity tests whenever natural environmental factors induce mortality above background levels.

Chronic toxicity of tributyltin to Chesapeake bay biota

Chronic tributyltin toxicity experiments were conducted with the following Chesapeake Bay organisms: amphipod, Gammarus sp.; juvenile Atlantic menhaden, Brevoortia tyrannus and larval inland silverside, Menidia beryllina. TBT concentrations ranging from 29 to 579 ng L−1 did not significantly affect survival of the benthic amphipod, Gammarus sp. after 24-d exposures. The weight of Gammarus exposed to control conditions was 2.8 times greater than the weight of these test organisms exposed to 579 ng L−1 TBT. Twenty-eight day exposures to TBT concentrations of 93 and 490 ng L−1 did not significantly affect survival of juvenile B. tyrannus or larval M. beryllina. Histological examinations of B. tyrannus did not demonstrate absolute effects resulting from TBT exposure due to extensive variation between individuals. Various morphometric measurements of M. beryllina after TBT exposure did not demonstrate significant effects. However, significant reductions in growth were reported for M. beryllina at both TBT concentrations. Environmental concentrations of TBT in Chesapeake Bay and possible effects on the above biota are discussed.

Effect of uranium on growth and reproduction of the marine amphipod Allorchestes compressa

Experiments on growth of the marine amphipod Allorchestes compressa Dana were carried out over four weeks, and both growth and reproduction were studied over three generations, each of which was exposed to uranium for approximately 10 wk. At 0.1 mg l-1 the uranium increased growth by 23%, as measured by the mean weight after 4 wk, and at 2 mg l-1 growth was reduced by 28% compared with the control. A. compressa accumulated uranium from sea water with a concentration factor of 10. There was no effect of uranium on the survival of amphipods or their progeny in the multiple-generation experiment, but the numbers of males, the sex ratio, and the respiration rate (measured on males only) at 1mg l-1 were significantly lower than the control. A. compressa is shown to be a convenient species for the study of toxic effects on growth and reproduction using multiple-generation experiments.