Production of benthic macroinvertebrates in a river used for commercial navigation: Kanawha River, West Virginia

The purpose of this study was to analyze the production of the benthic macroinvertebrates in a commercially navigated river in order to assess the environmental impacts of increasing levels of traffic. Production was estimated for 16 taxa at two sites in the Winfield navigational pool (Upper Winfield - UW; Lower Winfield - LW). Total production of all taxa on cobble/pebble substrates was 43,838 mgDW/m²/yr at UW and 16,553 mgDW/m²/yr at LW. Production on sand/silt substrates was lower, 3,534 mgDW/m²/yr at UW and 2,405 mgDW/m²/yr at LW. On cobble/pebble substrates the production was mostly accounted for by Diptera (76.0% UW, 85.2% LW), Trichoptera (12.4% UW, 5.8% LW), and Ephemeroptera (10.8% UW, 5.8% LW). On sand/silt substrates virtually all production was accounted for by Diptera. Total macroinvertebrate production for an "average" square meter of the Winfield Pool was estimated as 6,228 mgDW/m²/yr. It was estimated that 59.1% of the production in the pool came from cobble/pebble substrates at UW, even though these substrates only made up 8.4% of the available substrates. Approximately 57.8% of all production was attributed to detritus consumption, 18.5% to all types of algae, 23.8% to animal matter, and 0.3% to vascular plant materials. The benthic macroinvertebrate community consumes only a miniscule fraction of the organic materials flowing through the pool, however, the community forms an important energy pathway between the lower (detritus, primary production) and higher (fish) trophic levels. It appears that the structure and function of the benthic macroinvertebrate community has adjusted to the present levels of traffic, and it is not likely that an increased increment of traffic would have an adverse impact.