The seasonal community structure and drift of microcrustaceans in Valley Creek, Minnesota

Abstract

Microcrustaceans represent a poorly known component of stream systems. This study examined the seasonal abundance of copepods and cladocerans found in Valley Creek, Washington County, Minnesota. Both benthic densities as well as drift rates were quantified. A total of 16 species was collected in quantitative benthic samples and two additional species occurred in drift samples. The Valley Creek microcrustaceans could be classified into two general groups, those residing in depositional stream habitats similar to a lake or pond littoral and favoring an epibenthic lifestyle, and those found in more erosional habitats where a hyporheic lifestyle is more likely. The microcrustacean community also demonstrated a distinct seasonality with peak abundance in the spring and early summer. Sediment size compositon also demonstrated a seasonal change but detrital composition did not. Microcrustacean drift generally paralleled changes in benthic density but in several cases it tended to lag behind the changes in the benthos. This lag could be due to a seasonal siltation of the sediments, which would compress the habitat volume available to interstitial meiofaunal elements.