Macrobenthic distribution and community structure in the upper navigation pools of the Upper Mississippi River

Abstract

The northern section of the Upper Mississippi River supports a diverse macrobenthic assemblage. Distribution of this benthic fauna, benthic community structure, and factors which influence both of these phenomena in these upper pools are reviewed. Dumping of heavy loads of municipal and industrial wastes from the Minneapolis-St. Paul metropolitan area has severely stressed the benthic community. Once abundant, pollution-sensitive mayflies, Hexagenia bilineata and H. limbata, are noticeably absent, replaced by pollution-tolerant oligochaetes and midges (notably Chironomus). Harmful effects of this pollution are not restricted to the area immediately downstream from the Twin Cities. In Lake Pepin, the Hexagenia population has suffered a drastic decline. The benthic community is characterized by low species diversity and a dominant, pollution-tolerant Chironomusplumosus -Oligochaeta -Sphaeriidae -Hirudinea community complex. Farther south, effects of the high organic load which originates approximately 226 km upstream are ameliorated. Inundation of large, diverse land areas contributes to the great ecological diversity in Pools No. '7 and NO. 8. In Navigation Pool No. 7, benthic standing crops in the backwater pool areas (biomass range: 2.08-26.96 g mm2) exceed those in the main channel (biomass range: 0.05 -1.02 g rne2). Greater numbers of burrowing mayflies and mollusks were found in the pool areas. Of 131 taxa collected from 1976-1977 in Lake Onalaska, which occupies most of Pool No. 7, eight dominant groups -Oligochaeta, Hirudinea, Isopoda, Amphipoda, Lepidoptera, Diptera, Gastropoda, and Pelecypoda -accounted for 90-93% of the macroinvertebrates. In Pool No. 8, over half of the 144 benthic taxa collected during the summer of 1975 were insect nymphs and larvae. Oligochaetes were by far the most ubiquitous and dominant macroinvertebrates. Habitat preferences of particular benthic forms reflected distributional relationships between macroinvertebrates and physical-chemical conditions. Benthic production, in terms of total wet weight mm2 and macroinvertebrate density in each study area, was generally greater in the more eutrophic areas. However, fewer taxa were supported in these areas. These taxa were generally pollution-tolerant organisms, such as oligochaetes and certain chironomids, which were capable of burrowing into depositional-type substrates. More taxa and greater numbers of gill breathers and filter feeders, such as caddisflies, mayflies, stoneflies, and dipterans, were collected from less eutrophic areas.

An Evaluation of the Relative Quality of Dike Pools for Benthic Macroinvertebrates in the Lower Missouri River, Usa

“…Even though our study did not examine the difference in benthic communities between dike pools and other depositional areas (sand bars, silt bars, clay bank), previous large river studies have demonstrated that substrate composition is one of the factors directly influencing the diversity and abundance of benthic animals in these habitats (Anderson and Day, ; Beckett and Pennington, ). There is evidence that there may be an optimum distribution of particle sizes and quantity of organic matter for burrowing invertebrates such as midges (Chironomidae) and Hexagenia mayflies in depositional areas of large rivers (Eriksen, ; Wright and Mattice, ; Elstad, ). Sediments with more silt and clay retain higher amounts of organic matter (Culp et al , ; Hornbach et al , ) and are known to contain higher densities of macroinvertebrates (Carter et al , ; Anderson and Day, ).…”

Environmental and macroinvertebrate dynamics in the Lower Rhône River and a lateral dike field: a study matching two functioning descriptors

“…This could be explained by an important primary production (aquatic rooted macrophytes, perilithon and periphyton); the development of such vegetation resulting from the reduced current velocity and deposition of fine sediment (silt and clay), like in the deep and relatively quiet pools of the Missouri and the Mississippi rivers Elstad, 1986). All these environmental factors favour colonization of the dike field by specific lentic taxa (e.g.…”

“…Connections and submersions induce a high temporal variability of the habitat in the dike field and maintain a spatial diversity of the substrates (sand, in erosive zone and silty mud, in deposition areas). This double variability should act on the richness of the fauna (Elstad, 1986;Grzybkowska, 1989), but, without consideration of the Diptera Chironomidae, which contain a high number of species (Thieneman, 1954), no conclusion can be made on this point. On the second hand, connections and submersion induce an increase of the biological lateral exchanges (Amoros & Roux, 1988;Amoros, 1991).…”

Declining populations of the fingernail clamMusculium transversum in the upper Mississippi River

“…Musculium transversum previously composed a substantial proportion of the density and biomass of the benthic fauna (Sparks, 1980;Elstad, 1986). In addition, fingernail clams had been important in the diets of certain waterfowl (particularly lesser scaup Aythya affinis; Gale, 1973;Thompson, 1973) and bottom-feeding fishes (Starrett, 1972;Jude, 1973).…”