Evaluating the Impacts of Winter Drawdown on Macroinvertebrate Communities Within the Context of Localized Environmental Conditions

Download or read book Evaluating the Impacts of Winter Drawdown on Macroinvertebrate Communities Within the Context of Localized Environmental Conditions written by Gabrielle Trottier and published by . This book was released on 2016 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: "The regulation and management of lake water levels have become a major form of anthropogenic disturbance in temperate and boreal aquatic ecosystems. Drawing the water level down as the winter season progresses can lead to substantial exposure of the littoral zone, rendering it susceptible to desiccation and freezing. Such changes in the hydrological regime of littoral zones can have significant effects on aquatic biota, including macroinvertebrates. These organisms are widely considered as robust bioindicators, but it is also well known that their abundance and distribution is characterized by substantial patchiness. Often, scientists who use macroinvertebrates as bioindicators, focus their sampling on a single habitat type (e.g., stony littoral) to reduce the heterogeneity in macroinvertebrate distributions. However, applying such an approach in the context of an environmental stressor makes it difficult to draw general conclusions about the impact of a potential stressor on the entire littoral zone. Recently, a debate has emerged in the literature over the effects of water level drawdown on macroinvertebrate communities and we think that at least part of this debate may be due to different sampling strategies employed across studies to examine the effects of drawdown on macroinvertebrate communities. In order to evaluate how nearshore macroinvertebrate communities, from a variety of habitats, are affected by drawdown, we sampled 15 reservoirs and quantified macroinvertebrate abundance and composition. To these data, we applied a combination of (generalized) linear mixed effects models and multivariate analyses to answer the following question; what are the effects of drawdown on macroinvertebrate abundance and community composition? To address this question and incorporate the possible effects of heterogeneity in abundance and distribution of macroinvertebrates, we explicitly considered multiple physical environmental variables as additional predictors of macroinvertebrate abundance and community composition. We found that drawdown and thermal regime were significant predictors of macroinvertebrate abundance, but explained negligible amounts of variation in the community composition. Overall, these findings help elucidate how macroinvertebrate communities respond to winter drawdown and strengthen the knowledge on how localized environmental conditions influence macroinvertebrates. Furthermore we think that our sampling and analytical approach provides a useful template for other scientists to adopt when quantifying the effect of a potential stressor on nearshore macroinvertebrate communities." --