The influence of stream habitat and water quality on macroinvertebrate communities in degraded streams of northwest Mississippi

Streams in the loess hills of northwest Mississippi have undergone dramatic physical changes since European settlement and both physical and water quality processes may play a role in influencing biotic communities of these stream systems. The objectives of this study were to identify the response of macroinvertebrate taxa to water quality and habitat parameters in streams of northwest Mississippi, examine the efficacy of an a priori classification system of stream channel evolution and condition class using macroinvertebrate communities, and examine short-term (<2 yr) temporal variation of macroinvertebrate communities. Separation of sites based on four condition classifications was not distinct. However, best attainable sites did plot together in an ordination analysis suggesting similarity in macroinvertebrate communities for least disturbed sites. Similarly, for stage of channel evolution, sites characterized by lack of bank failure and sinuous fluvial processes had relatively similar macroinvertebrate communities. Ordination analysis also indicated high temporal variation of macroinvertebrate communities. Reference sites (best attainable and stable sites) had more similar communities between years than unstable and impacted sites. Results of this study: (1) suggest total solids, total phosphorus concentration, percent substrate as sand, ammonia concentration, and conductivity were important variables for structuring stream macroinvertebrate communities in northwest Mississippi, (2) identify potential indicator taxa for assessing such streams based on water quality and physical habitat, (3) provide support for current a priori site classifications at the best attainable (least impacted) category relative to the macroinvertebrate communities, and (4) demonstrate that between-year variation is an important factor when assessing streams of north Mississippi and this variability may be related to the degree of stream degradation.