Community structure during a 27-year study of the macroinvertebrate fauna of a chemically unstable lake

Abstract

Data are given on summer temperatures, conductivity, vegetation cover and the quantitative species composition of macroinvertebrates in each of the years 1968–1994. It is demonstrated that species composition, species richness and numbers of individuals varied from year to year. Community structure is expressed by species richness, species diversity, equitability and rank-abundance graphs. Species richness showed a highly significant negative correlation with conductivity and a highly significant positive correlation with vegetation cover. However, the highest significance found was with the sum of vegetation cover and the reciprocal of conductivity. Species diversity and equitability showed patterns of minima coinciding with summer temperature maxima. Rank-abundance graphs remained relatively constant throughout the study period and were used to demonstrate that a niche pre-emption model, with modification to accomodate a power graph, provided an adequate model for all years. This model suggests a deterministic explanation, but with fluctuations dependent upon random or cyclical environmental factors.