Ecological factors influencing macroinvertebrate standing crop distribution

Abstract

Influence of substrate, macrophyte growth and detritus on macroinvertebrate standing crop (numbers and biomass) as well as seasonal variations in standing crop were investigated in a trout stream .Ephemeropterans showed no consistent relationship to substrate type, either in numbers or biomass. Numbers of dipteran larvae (primarily chironomids and simuliids) did not show a definite relationship to substrate size . But a larger biomass was associated with larger substrates . Higher numbers and biomass of trichopterans (including Helicopsyche borealis) were associated with larger substrates . Numbers of coleopteran larvae showed no relation to substrate size, but biomass was greater in large substrates . Biomass and numbers of water mites were generally associated with larger substrates, whereas no relationship was observed in plectopterans .Larger numbers and biomass of ephemeropterans, dipterans (chironomids and simuliids but no other dipterans) and trichopterans are associated with macrophyte beds ; this is attributed to drifting species and those that have summer generations . Macrophyte growth reduced numbers and biomass of H. borealis, but no differences were observed in coleopterans or plecopterans .A substrate/detritus substitution study was done under natural stream conditions. An area of relatively constant current and depth was selected from which eighteen sites were randomly selected . Gravel and detritus were removed and replaced with two distinct sizes of substrate and three different levels of detritus . This was a 2 x 3 factorial analysis design . Ephemeropteran numbers were significantly related to substrate type and detritus level, whereas biomass was only related significantly to substrate . Numbers of chironomids and other dipterans responded significantly to substrate manipulation . Biomass of dipterans other than chironomids was significantly related to substrate type but not detritus level and chironomid biomass did not respond to either manipulations .Trichopteran numbers responded significantly to substrate and detritus manipulations, whereas biomass was significantly related only to substrate type . Analysis of variance showed that coleopteran numbers did not respond significantly to either manipulation ; however, orthogonal contrasts showed that, within large substrate, medium detritus level was significantly different from high detritus level . Oligochaetes did not respond to either substrate or detritus manipulation . The responses of the organisms to manipulations are explained in relation to interstitial spaces and oxygen as well as the interaction between substrate type and amount of detritus .

Microhabitat preferences of benthic fauna in a woodland stream

“…Although, it is generally accepted that abundance of stream benthos increases along a gradient of increasing particle size from sand through boulders (Wene & Wickliffe, 1940;Pennak & Van Gerpen, 1947;Sprules, 1947;Barber & Kevern, 1973;Ward, 1975), in our study, size of the predominant substrate particle was significantly related to the abundance of only one species, Microcylloepus pusillus (Fig. 6).…”

Indicator value of lotic water mites (Acari: Hydrachnidia) and their use in macroinvertebrate-based indices for water quality assessment purposes

“…Despite sharing these characteristics with other macroinvertebrates, water mites are rarely utilized as bioindicators of pollution or disturbance (Resh and McElravy, 1993;Dohet et al, 2008). In the rare cases of inclusion in studies of invertebrate-environment associations and invertebrate-based indices of environmental quality, water mites are typically treated as a single taxonomic unit ("Hydrachnidia": e.g., Barber and Kevern, 1973;Pardo and Armitage, 1997;Kubošová et al, 2010;Alvial et al, 2013); however, water mites have been altogether excluded from the WFD list of biological parameters (Smit and Gerecke, 2010). The main scopes of our work are 1. an assessment of water mite value as bioindicators based on an analysis of abundance and diversity as related to varied levels of pollution, and 2. the proposal of a numerical index of water quality for running-water ecosystems that includes water mites at family level.…”

Production of Cricotopus ornatus (Meigen) (Diptera: Chironomidae) in Waldsea Lake, Saskatchewan

“…Sandy to sandy-mud substrates supporting macrophyte or benthic algal growth had significantly higher populations than mud-detritus substrates which usually corresponded with the deeper sampling strata (4-6 m), where oxygen concentrations and temperatures were lower and macrophyte and benthic algal growth minimal or absent. Association of large numbers of the genus Cricotopus with macrophyte beds has been reported by a number of workers (Sandberg 1969;Korinkova 1971;Gak et al 1972;Barber & Kevern 1973;Menzie 198 1).…”