Seasonal variations in the benthos of a chalk trout stream,the River Samson,Belgium |
| |
Authors: | Dominique Rosillon |
| |
Affiliation: | (1) Unité d'Ecologie des Eaux Douces (U. N. E. C. E D.), F. N D. P., 61, B-5000 Rue de Bruxelles, Namur, Belgium |
| |
Abstract: | Seasonal variations in the benthos of a Belgian chalk stream were investigated. Total biomass varies extensively over the year (30 to 100 g wet wt. m–2). In summer, however, it is smaller than fish biomass. Densities range from 30 000 to 50 000 individuals m–2, but the actual number of taxa is always near 60. Diversity indices (Shannon-Weaver and Pielou) exhibit slight fluctuations. Numerical indices are minimal in winter when the stream is in flood. Gravimetric indices are minimal in spring when biomass is maximal. Species-abundance curves almost always indicate a fauna with many rare species, with, also, some indication of a second maximum of moderately abundant species. Six taxa dominate: Oligochaeta, Gammarus fossarum, Ephemeroptera, Coleoptera, Trichoptera and Diptera. There are great fluctuations in their relative importance over a year. Thus, there seems to be a succession of peaks in densities of individual taxa permitting more efficient utilization of resources. However, biomass variations depend on the species involved. As a general rule, maximum biomass precedes maximum density. |
| |
Keywords: | benthos abundance biomass seasonal changes |
本文献已被 SpringerLink 等数据库收录! |
|