Spatial variation in headwater stream macroinvertebrate abundance and diversity

We studied headwater streams in Delaware County, Indiana to quantify differences in macroinvertebrate assemblages.  We hypothesized that macroinvertebrate indices would differ with surrounding land-use.  Weekly water samples and physiochemical measurements were collected from May-August 2008 in conjunction with macroinvertebrate samples collected with surber nets.  Macroinvertebrates were brought back to the laboratory and identified to the genus level.  Percent chironomidae, percent dominant taxa, EPT, family richness, and the Hilsenhoff Family-Level Biotic Index (H-FBI) were calculated for each stream.  Streams with high H-FBI had low family richness, high percent chironimidae/oligochaeta counts, and high percent dominant taxa counts.  Conversely, sites with low H-FBI readings had higher family richness, lower percent chironomidae/oligochaeta counts, and lower percent dominant taxa counts.  All streams, however, had high H-FBI readings relative to previous studies which are indicative of organic pollutants.  Sites with higher sulfate concentrations had more intolerant taxa present as represented by the H-FBI.  However, family richness increased with sulfate concentration.  Percent dominant taxa decreased with stream nitrate concentrations.  Very low EPT values at all sites made the index ineffective at showing differences between sites and is indicative of highly degraded systems.  This is most likely a result of high agricultural and urban land-use in the areas surrounding the streams.