Salinization of freshwater ecosystems as a result of human activities has markedly increased in recent years. Much attention is currently directed at evaluating the effects of increased salinity on freshwater biota. In the Central Appalachian region of the eastern United States, specific conductance from alkaline discharges associated with mountain top mining practices has been implicated in macroinvertebrate community declines in streams receiving coal mining discharges. Whole effluent toxicity testing of receiving stream water was used to test the hypothesis that mine discharges are toxic to laboratory test organisms and further, that toxicity is related to ionic concentrations as indicated by conductivity. Chronic toxicity testing using Ceriodaphnia dubia was conducted by contract laboratories at 72 sites with a total of 129 tests over a 3.5 year period. The database was evaluated to determine the ionic composition of mine effluent dominated streams and whether discharge constituents were related to toxicity in C. dubia. As expected, sulfate was found to be the dominant anion in streams receiving mining discharges with bicarbonate variable and sometimes a substantial component of the dissolved solids. Overall, the temporal variability in conductance was low at each site which would indicate fairly stable water quality conditions. Results of the toxicity tests show no relationship between conductance and survival of C. dubia in the mining influenced streams with the traditional toxicity test endpoints. However, consideration of the entire dataset revealed a significant inverse relationship between conductivity and neonate production. While conductivity explained very little of the high variability in the offspring production (r2 = 0.1304), the average numbers of offspring were consistently less than 20 neonates at the highest conductivities.

This chapter provides an overview of the use of nematodes as test organisms for ecotoxicity testing. Exemplary studies that investigated the toxicity of single substances or environmental samples on nematodes, regarding different nematode species, toxicity endpoints and test substrates are reviewed. The main focus is on the most frequently used species, Caenorhabditis elegans, by presenting examples and case studies, where this test organism has been used in ecotoxicological assessments.

Freshwater ecosystems are known to be impaired by disturbances within their watersheds.These disturbances may result from multiple sources ranging from resource extraction to development (e.g. urban, residential, industrial, and commercial). Even low level disturbances have been shown to result in impairment to stream biota within the watershed. However when very low levels of disturbance occur, the mechanisms, resulting in impairment to the biological integrity of the freshwater ecosystem, are not known. The objective of this study is to examine the immediate effects of an anthropogenic disturbance of less than 1% of the watershed area. Baseline conditions were established and total suspended solids (TSS) and substrate mobility, were monitored and compared between pre and post disturbance conditions. Disturbance was created by timbering a 0.24 acre area in the 89 acre watershed. The stream was separated into three different reaches: Site 1 (the downstream recovery reach), Site 2B (immediately downstream of disturbance) reach), and Site 3 (the upstream control reach). The data shows variation, at the sites, in suspended and settled sediment as indicated by TSS and substrate mobility. Sites downstream of the disturbance, Site 2B and Site 1, increased in substrate mobility compared to the up gradient site (Site 3). Suspended sediment increased at all three sites post-disturbance.

Mayflies may be more sensitive to aquatic contaminants than surrogate test organisms used to determine anthropogenic effects on aquatic ecosystems. While toxicity testing could be utilized to establish a direct link between contaminants of concern and mayfly mortality, potentially more sensitive mayfly taxa are not readily available for use in toxicity testing.Methods for rearing larval mayflies to emergence, collecting viable eggs and rearing them to hatch have been developed. Further development of the methods in order to conduct native mayfly toxicity testing is dependent on a suitable food source being established for cultured mayfly nymphs. The objective of this study was to find a suitable food source for newly hatched Baetidae nymphs to increase longevity of newly hatched nymphs. Success will be evidenced by the growth and development of the nymphs. Preliminary evaluations utilizing a variety of natural and laboratory cultured diets given to individual nymphs in separate chambers were conducted. Mortality and growth were used to narrow food types to the ones yielding the best results for further testing. Ten of the eleven feeding treatments maintained adequate survival of newly hatched mayflies for 3 days but only 2 of the treatments, the first being a mixture of diatoms collected from Hammack Hollow and Selenastrum sp., and the second being leaf disks, supported greater than 70% survival to 6 days. While mortality was high in all treatments between 6 and 9 days, diet combining Selenastrum sp., yeast, cereal leaves and trout chow (YCT), and leaf disk supported the greatest survival over the 24 day study.

Prymnesium parvum blooms result in fish kills around the world and are devastating to fish hatcheries, where few management tools are available. Current control strategies include algaecides, nutrient management, and flocculation, which are moderately effective at best and can be toxic to nontarget organisms. A relatively new type of medium, registered by the U.S. Environmental Protection Agency for the control of fecal coliforms in storm water runoff, was evaluated as a possible P. parvum control tool. The medium, called Smart Sponge, was designed to absorb petroleum hydrocarbons; a variant, Smart Sponge Plus, is enhanced with antimicrobial properties. It is these antimicrobial properties that we investigated for possible use in algal bloom management. Our objective was to evaluate the efficacy of this type of medium on the eradication of P. parvum and its associated toxins, with a view toward advancing toxic algae control strategies. Prymnesium parvum was passed through columns of the filter medium. Algal cell counts and visual observations were used to assess mortality; fish bioassays were conducted to assess toxicity. Smart Sponge Plus successfully killed the algae, although toxins were released during filtration. After filtration, 87–100% algal removal was achieved, with the variability potentially being related to cell density at the initiation of the test. Smart Sponge was also successful in reducing associated the toxicity of P. parvum, as was a charcoal medium. Smart Sponge Plus shows promise for use in the management of golden algal blooms by reducing cell density and should be further evaluated in hatchery and field settings.