Determination of the short-term response of aquatic macroinvertebrate communities to suspended sediment loading

A common cause of impaired rivers and streams in the US is sediment pollution. High levels of suspended sediment impact aquatic communities in different ways depending on the type and texture of the sediment.  However, many state regulatory programs use a water quality criterion based on turbidity alone, not taking into account sediment type or potential underestimate of total suspended sediment. To measure the differential impact of sediment types on benthic invertebrates, we introduced clay, fine sand, agricultural soil and an inorganic mixture to an experimental stream in a series of controlled floods. We measured the invertebrate response as drift and benthic community composition compared to a reference reach before, during, and after flooding. Sand and clay increased invertebrate drift relative to baseline conditions (p<0.01) and soil mixes (p<0.01). Clay releases also resulted in significantly lower invertebrate density (p<0.05).  Experiments occurred in a newly built sand-bed channel fed by Mississippi River water in the Outdoor StreamLab flume at the University of Minnesota.  A high density of invertebrates (3 cm^-2) colonized the channel in the first weeks after its construction and the resulting community was rich and included EPT taxa. The rapid colonization of this artificial channel has implications for restoration.