Epsilon Archive for Student Projects

Abstract

Multivariate statistical methods were used to explore the relationships between functional feeding guilds of different macroinvertebrate communities in Swedish streams and lakes.
The most important factor for explaining the composition of functional feeding groups, both in streams and lakes, seemed in Sweden to be geographical position ( e.g. altitude and ecoregion) and local scale factors ( e.g. substrate).
Principal component analysis (PCA) showed that abiotic factors, like stream velocity and geographical position, seemed to be important both in streams and lakes. Like PCA, redundancy analysis (RDA) showed that geographical factors were important for the functional feeding group composition of benthic communities in lakes. Forest in the catchment area and stream velocity were important for the composition in streams.
Using partial RDA, a total of 39.9% for stream data and 44.0% for lake data were explained. The unique variation of local scale factors seemed to be the most important factor to explain the variability of functional feeding groups, both in streams (59%) and lakes (44%), out of the total variation that could be explained.
Stream velocity in streams and geographical position in lakes also showed, in stepwise multiple regression, to be important factors for the functional feeding group composition. The highest adjusted r2-value for stream data was shown by passive filter-feeders (0.44), followed by grazers (0.40), detritus feeders (0.35), shredders (0.30), predators (0.28), and active filter­feeders (0.21). For lake data the highest adjusted r2-value was shown by detritus feeders
(0.54), followed by grazers (0.49), predators (0.27), active filter-feeders (0.29), shredders
(0.27), and passive filter-feeders (0.15).
The abundance of macro invertebrates showed for functional feeding groups in lakes, but not in streams, a tendency of increasing values from north to south in the country. Except for the alpine region, the functional feeding group composition of streams did not vary among ecoregions. In lakes, a significant difference in composition of functional feeding groups occured between the middle and southern boreal regions.
A field study comparing functional feeding group composition and fatty acid contents between arable and forested sites within a single stream was also done. No significant differences in functional feeding group composition were found except for active filter­feeders. Fatty acid composition was similar within, but different among the functional feeding groups analyzed between forested and arable sites.