"Transforming daphniid ecotoxicology for soft-water, nutrient-poor lakes in a warming, multi-stressor world."

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The animal plankton or zooplankton community of lakes is intrinsically interesting, and it also provides key ecological services to mankind passing food to fish, and maintaining water clarity in the process. However, recent changes in climate, water chemistry, food base and predators are confounding our ability to explain current and predict future changes in zooplankton. Ecotoxicological methods using the aquatic "white rat", Daphnia, should help explain the changes, but the majority of daphniid toxicology has a regulatory focus, designed to identify levels of contaminants that are lethal under standard lab, not natural conditions. Applying the results of regulatory toxicology to the field is problematic, because such work commonly uses species not found in our lakes, reared in waters not typical of our lakes, for durations that miss primaparity, often the most sensitive life stage. Further, animals are fed with algae that are not the dominant natural food, at levels typifying over-fertilized, not our normal, nutrient-poor waters. Using Daphnia isolated from our lakes, reared in media that reflects their chemistry, over durations reflecting primparity, I and my students will address these knowledge gaps, and in so doing transform the practises of daphniid ecotoxicology for Shield lakes. We will identify: 1) feeding schedules that produce fecundities typical of our lakes, 2) replicate sizes needed to distinguish effects at field-typical clutch sizes, 3) the influence of natural food quality on animal performance, and 4) differences of stressor effects among actual clones and species from our lakes, then 5) we will use our new methods to determine if calcium and phosphorus decline can explain the common loss of 5 daphnid species from our lakes, and 6) to determine whether ongoing metal toxicity is responsible for the slow recovery of Sudbury lakes. We will transform the methods of daphniid ecotoxicology, and in so doing dramatically increase our ability both to explain the complex changes that our occurring in nature, and to predict what may soon happen in our warming, human-dominated world. Ecologists, ecotoxicologists and lake and fisheries managers will realize long-lasting benefits from this work.