Assessing lake functioning using the macrobenthic community with special reference to Chironomidae (Diptera). A subalpine lake (Lake Annecy) as an example

摘要

The macrobenthic community of Lake Annecy was investigated through both a study of the total macrobenthic organisms living in the sediments and an extensive study of the chironomid community. Two sampling methods were used. Sediments were sampled in April 1998 with a modified Ekman grab at 36 sampling sites along four isobaths. At the same sites, chironomid pupal exuviae were collected for species identification at the water surface by net-dragging. Quantitative descriptors of the total macrobenthic and the emerging chironomid communities (i.e. total taxon richness, chironomid species richness, littoral biodiversity index, chironomid larval density) showed high values that reflect a high biogenic capacity. Qualitative descriptors of the communities (i.e. bathymetric pattern of taxon richness, specific composition of the chironomid community and bathymetric distribution of chironomid species) indicate that Lake Annecy is an oligohumic lake characterised by a decrease in organic matter content with depth. According to VERNEAUX et al. (1993 a, 1993b, 1995) biological classification of lakes the bathymetric pattern of the macrobenthic community of Lake Annecy is related to an optimal efficiency of organic matter assimilation within the food web (optimal functioning). [References: 40]