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Sedimentation of Prairie Wetlands

Effects on Aquatic Invertebrates

Any suppression of primary production from sedimentation would be expected to negatively impact wetland invertebrates. The loss of standing vegetative structure generally makes wetlands less productive of invertebrates (Krecker 1939; Krull 1970; Euliss and Grodhaus 1987). Recent studies stressing the nutritional value of algae to invertebrates (Neill and Cornwell 1992) suggest that loss of algal biomass especially periphyton and phytoplankton, also would make wetlands less productive of invertebrates. Direct impacts of turbidity and sedimentation may include covering of invertebrates eggs, the clogging of filtering apparatuses, and the covering of organic substrates important in aquatic food chains (Swanson and Duebbert 1989). High levels of suspended silt and clay have been shown to be toxic and to reduce zooplankton feeding rates and assimilation (Robinson 1957; McCabe and O'Brien 1983; Newcombe and MacDonald 1991). Further, impacts of sediment on aquatic invertebrates and plants may be exacerbated in the presence of other stressors such as agrichemicals when sorbed to sediments (Hartman and Martin 1984, 1985). For example, the acute toxicity of the agricultural herbicide glyphosate is increased for water fleas (Daphnia pulex), but suppressed for duck weed (Lemna minor) when adsorbed to suspended sediment (Hartman and Martin 1985). Glyphosate adsorbed on suspended sediment was apparently ingested by water fleas (Daphnia pulex) and thus provided a direct route of exposure, whereas adsorption of glyphosate on sediment rendered it unavailable to duck weed (Lemna minor).
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