Distribution and abundance of littoral benthic fauna in Canadian prairie saline lakes

Abstract

The littoral benthos of 18 lakes in Alberta and Saskatchewan ranging in salinity from 3 to 126‰ (g1⁻¹ TDS) were investigated twice, in the spring and in the summer of 1986. Multiple Ekman dredge samples were taken at water depths of about 0.5, 1.0 and 2 metres in each transect. Two to three transects were used in each lake according to its estimated limnological diversity for a total of 114 stations. A total of 76 species was present varying from 29–31 species in the three lakes of lowest salinity (means of 3.1–5.55‰) to only 2 species in lakes exceeding 100‰. Species richness decreased rapidly in salinities greater than 15‰.

Biomass maximum mean of 10.91 g m⁻² dry weight (maximum 63.0 g m⁻²) occurred in culturally eutrophic Humboldt Lake (3.1‰) but one third as great in other low salinity lakes. However, biomass again increased to about 4.5 gm⁻² in two lakes of 15‰ As the salinity increased still further biomass declined steadily until a minimum of 0.0212 g m⁻² was recorded in most saline Aroma Lake (mean 119‰). Summer biomass (11 lakes) was greater than spring biomass (4 lakes) because some groups such as amphipods, corixids and ostracods became more abundant in summer. Wet weight biomass averaged 15.8‰ of dry weight biomass.

Seasonality (spring or summer), sediment texture and organic matter content, water depth, pH, salinity (TDS) and the presence of aquatic plants (‰ plant cover) were considered in the matrix involving species dry weight biomass at each of 117 stations. TWINSPAN classification of the samples yielded a dendrogram with 18 indicator species. Successive dichotomies divided these indicator species into four main lake groups based on salinity, i.e., Group I: 3–10‰ (Gammarus, Glyptotendipes I, Chironomus cf. plumosus), Group II: 10–38%. (Hyalella, Enallagma,Bezzia), Group III: 38–63‰ (Hygrotus salinarius, Cricotopus ornatus), Group IV: >63‰ (Dolichopodidae, Ephydra hians). Each of these main groups was subdivided into smaller groups of lakes based on factors such as pH, seasonality (spring or summer species dominance), ‰ organic matter and ‰ plant cover. Depth of samples played no apparent role.