Influences of habitat type and environmental variables on littoral macroinvertebrate communities in a large lake system
Tolonen, K. T.; Hämäläinen, H.; Holopainen, I. J.; Karjalainen, J.
published: Jul 19, 2001
ArtNo. ESP141015201009, Price: 29.00 €
The community structure of littoral macroinvertebrates was explored by multivariate analyses in three basins of the large Lake Saimaa system (eastern Finland). The basins differed in trophic status and degree of human influence. It was hypothesized that the structure of littoral invertebrate communities is influenced by lake trophic status, as is the case in profundal communities. Three littoral habitat types with different substrate (stony, sandy and vegetated shores) were sampled from the shoreline to a depth of 1.5-3 meters. The habitat type was found to be largely determined by the slope of the shore and the wind exposure. Each habitat type supported fairly characteristic fauna, and detrended correspondence analysis grouped the invertebrate assemblages by habitat type rather than by basin. Within each habitat type, canonical correspondence analysis indicated that species composition changed along the trophic gradient. In the vegetated littoral zone, the greatest change in community structure occurred within the macrophyte beds, varying from the outer edge of macrophytes to the shoreline. Two alternative or complementary explanations are given for this horizontal gradient. First, a horizontal gradient of abiotic characteristics results in a change of community composition. Second, the macrophyte beds may form a horizontal transition zone in predation, from invertebrate predation inshore to fish predators offshore. On the stony and sandy shores, the magnitude of wave action was also important in structuring the communities. As each habitat type harbors characteristic fauna, a variety of habitats needs to be protected in order to conserve littoral macroinvertebrate diversity in large lakes. To make among-lake comparisons of littoral macroinvertebrate assemblages, stratification by habitat type is obviously necessary. The effects of eutrophication on invertebrate assemblages were most pronounced in stony habitats.