Sediment from lake with missing egg bank is toxic to hatchlings of model zooplankton: A reason to consider obligate dormancy in toxicological assessment.

Over the last 60 years, valuable progress was made in the standardization of environmental monitoring with model zooplankton. However, obligate dormancy in zooplankton life cycles is not yet considered in standardized toxicology methods. Most zooplankton from coastal and inland waters use dormancy as a critical ecological strategy, and exposure to toxicants during dormancy or resurrection from dormancy alters developmental patterning and hatching success. The present study accounts for this by using both standardized and novel toxicology assays to assess the impacts of coal ash contaminated sediments and water on development, hatching, and survivorship of model zooplankton. The results demonstrate that standardized assays with rotifer and cladoceran models detect no toxicity in surface water and sediment pore water from Lake Sutton, North Carolina, USA. By contrast, novel toxicity assays with cladoceran and anostracan models demonstrate that development and larval survivorship are negatively impacted by Lake Sutton water and sediment. Embryos of Artemia franciscana display developmental patterning and hatching aberrations that match those observed in previous studies with metals when hatched in filtered surface water or pore water after a period of anoxia-induced dormancy. Larval survivorship in Daphnia magna and A. franciscana also decreases when post-diapause embryos are hatched in the presence of sediment. The effects of whole sediment on larval survivorship are not explained by coal ash impacts on water pH. These data provide an explanation for the missing egg bank and historic community restructure in Lake Sutton. The data also demonstrate a need for standardized assays that include dormant life stages.