Factors Controlling Nickel Bioavailability and Effects On Benthic Invertebrates in Hardwater Freshwater Streams

Sediments in aquatic ecosystems function ecologically as habitat, food, and refugia that aid in reproduction processes, and chemically as sources and sinks for contaminants. Sediment contamination from metals and organics has been linked to numerous health and ecological effects, extending from fish consumption advisories to endangered species listings. This dissertation research examines Ni bioavailability (simultaneously extracted metal (SEM)/acid volatile sulfide (AVS) models) and toxicity in five separate studies using Ni-spiked sediments in a variety of designs, and mainly with two different sediment types (low AVS, total organic carbon (TOC), and high AVS, TOC). Two separate streamside mesocosm Ni experiments indicated that benthic communities (Ephemeroptera, abundance, taxa richness) responded negatively to increasing SEMNi/AVS and (SEMNi-AVS)/ƒoc models (increasing Ni bioavailability), and these communities demonstrated a sediment type preference. During a Ni-sediment flow-thru study, Ni toxicity was tested on four indigenous aquatic insects (Anthopotamus verticis, Stenonema spp., Isonychia spp., and Psephenus herricki) and two surrogate organisms (Hyalella azteca and Chironomus dilutus). Of the indigenous insects, A. verticis and Stenonema spp. were the most sensitive to Ni-spiked sediments in this study. Overall, H. azteca was the most sensitive to total Ni, and A. verticis was most sensitive to the bioavailable fraction (SEMNi/AVS). Ni toxicity then examined natural benthic macroinvertebrate community colonization on two different sediment types at three different sites (Ohio and Michigan) in situ. Taxa richness, abundance, and % EPT responded negatively to increasing SEMNi/AVS values, and site differences were observed. Finally, H. azteca and Lymnaea stagnalis were exposed to a series of tests involving singular or combinations of Ni amendments to water, sediment, and food (stable isotope 62Ni) with dissolved organic carbon (DOC), total suspended solids (TSS) water amendments on two sediments types. Both organisms demonstrated numerous survival, growth, and feeding inhibition effects to these Ni-water and Ni-sediment tests. DOC provided a protective survival, growth, and bioaccumulation (62Ni) effect on L. stagnalis. Overall, H. azteca and L. stagnalis responded similarly with regard to food uptake and trophic transfer of 62Ni, which suggested little 62Ni transfer from food sources. There are fewer studies and data available for the ecotoxicity of Ni, and these studies help discern Ni bioavailability on a range of aquatic organisms and benthic macroinvertebrate communities. This research has better elucidated the toxicity of Ni in freshwater ecosystems, demonstrating the importance of a range of physicochemical factors on Ni bioavailability, and the relative importance of the three primary exposure routes: water, sediment, and food