Benthic invertebrates are aquatic animals without backbones that dwell in or on the bottom sediments of streams and lakes. Some benthic invertebrates that you might be familiar with are larval insects such as caddisflies and mayflies, as well as clams and a wide variety of worms.
Benthic invertebrates play a critical role in the flow of energy through riverine ecosystems. They typically function as key primary and secondary consumers and are often favoured prey of keystone (and other) species of fish. Benthic invertebrate communities also reflect their environment and are indicators for water quality and overall river health (e.g., oxygen conditions).
A project is currently underway in the Milk River watershed that seeks to understand long-term changes in macroinvertebrate (benthic invertebrate) communities within five selected reaches of the Milk River in southern Alberta. These sites were first sampled by Beth Cornish in 1986 (Cornish, 1988). The sampling done by Cornish provides a unique opportunity to evaluate changes over a period that includes both the highest (1995) and lowest (2004) river flows on record. Data collected in this study will be linked to land use, water quality and fish habitat.
Between September 30 and October 7, 2008 the five sites documented by Cornish (1988) were revisited by the University of Lethbridge. There are 25 samples to evaluate for macroinvertebrate diversity and density, with benthic invertebrates being identified and counted. The data is being analyzed and results of the study will focus on long-term changes in the benthic invertebrate communities between the two time periods.
The results of this study will be presented at the Milk River Watershed Council Canada Annual General Meeting on April 9, 2009.