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A novel experimental approach to assess the effect of contamination events on the spatial distribution of organisms in lotic-estuarine landscapes

Abstract:

The riverscape concept includes structural connectivity and functional interactions where upstream processes significantly influence downstream conditions. As such, a landscape perspective is necessary to evaluate the impact of contamination, because it can spread far beyond the release area, potentially reaching estuaries. Therefore, we hypothesized that contamination might affect freshwater organisms' habitat selection in a simulated lotic-estuarine (flow-through) landscape, considering that the estuary zone acts as a stress factor by restricting the options of habitats while the non-contaminated upstream areas could serve as shelter zones to alleviate or even prevent the contamination exposure. The aim of this study was to provide a new method to evaluate the habitat selection response of aquatic organisms when exposed to a contamination event in a simulated lotic-estuarine landscape, including upstream and shelter zones as attractive habitats and an estuary zone. The freshwater shrimp Atyaephyra desmarestii was used as model test organism, copper was used as the contaminant, and the Heterogeneous Multi-Habitat Assay System (HeMHAS), was employed to simulate the lotic-estuarine landscape with a multiple connectivity setup. The results showed that contaminated conditions led shrimp to avoid the contaminated area and were carried towards the estuary region with the flow. However, in a static experiment (without flow), both estuary and contaminated regions were avoided and a preference for the shelter (clean) regions was observed. This study highlights the plasticity of organisms’ habitat selection behavior within a connected ecosystem, where contamination and salinity pressure together might have serious implications for the distribution of freshwater species. Further, the HeMHAS can successfully integrate flow in simulated heterogeneous landscapes to broad the understanding of contamination effects in aquatic lotic ecosystems.