Author: Publisher:
ISBN:
Category : Freshwater invertebrate populations
Languages : en
Pages : 0
Book Description
There is a growing concern on the potential ecological effects of what appears to be recent declines in aqueous calcium (Ca) concentrations in softwater lakes in the Canadian Shield. The relative importance of calcium concentration on littoral macroinvertebrate community structure was investigated in six lakes within the Nipissing and Muskoka districts in Ontario, Canada. Benthic macroinvertebrates and water chemistry were sampled in the fall and sorted using the standard Ontario Benthos Biomonitoring Network protocols (OBBN) for lakes. Differences in community structure and density amongst the lakes were quantified using principle component analysis, canonical correspondence analysis and a series of one-way ANOVAs. The results indicated that habitat preferences of certain macroinvertebrates play a big role in the community structure of invertebrates within a lake. However, it was found even in preferential habitat (macrophyte, rock, silt, sand and detritus), the presence of gastropods in lakes were insignificant and often absent from sites and lake with low Ca concentrations. Amphipods displayed similar densities and composition in lakes sites with the similar Ca concentration and habitat (macrophytes, cobble and roots). Consequently, changes in Ca concentrations greatly reduced amphipods density, regardless of similar habitat. Bivalves were shown to be greatly associated with both habitat (buried in substrate) and the availability of environmental Ca in the lakes. In general, it was observed that lakes with higher Ca concentrations, generally above 2 mg/L were shown to have greater macroinvertebrate densities, in comparison to lakes with Ca concentrations below 2 mg/L. Plastic Lake (Ca= 0.96 mg/L) had the lowest abundance of crustaceans and molluscs between lakes. This result suggests that crustaceans and mollusc abundance in lakes can be greatly reduced when Ca concentrations drop below 1.00 mg/L altering community structure. Calcium sensitive groups, such as gastropods and amphipods within the crustaceans and molluscs family, were found to have higher abundance numbers in higher calcium lakes.