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.

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.

The Ohio River Basin (ORB) is responsible for 35% of total nitrate loading to the Gulf of Mexico yet controls on nitrate timing require investigation. We used a set of submersible ultraviolet nitrate analyzers located at 13 stations across the ORB to examine nitrate loading and seasonality. Observed nitrate concentrations ranged from 0.3 to 2.8 mg L −1 N in the Ohio River's mainstem. The Ohio River experiences a greater than fivefold increase in annual nitrate load from the upper basin to the river's junction with the Mississippi River (74-415 Gg year −1 ). The nitrate load increase corresponds with the greater drainage area, a 50% increase in average annual nitrate concentration, and a shift in land cover across the drainage area from 5% cropland in the upper basin to 19% cropland at the Ohio River's junction with the Mississippi River. Time-series decomposition of nitrate concentration and nitrate load showed peaks centered in January and June for 85% of subbasin-year combinations and nitrate lows in summer and fall.Seasonal patterns of the terrestrial system, including winter dormancy, spring planting, and summer and fall growing-harvest seasons, are suggested to control nitrate timing in the Ohio River as opposed to controls by river discharge and internal cycling.The dormant season from December to March carries 51% of the ORB's nitrate load, and nitrate delivery is high across all subbasins analyzed, regardless of land cover. This season is characterized by soil nitrate leaching likely from mineralization of soil organic matter and release of legacy nitrogen. Nitrate experiences fast transit to the river owing to the ORB's mature karst geology in the south and tile drainage in the northwest. The planting season from April to June carries 26% of the ORB's nitrate and is a period of fertilizer delivery from upland corn and soybean agriculture to streams. The harvest season from July to November carries 22% of the ORB's nitrate and is a time of nitrate retention on the landscape. We discuss nutrient management in the ORB including fertilizer efficiency, cover crops, and nitrate retention using constructed measures.

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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.