INVERTEBRATE COMMUNITIES ASSOCIATED WITH MACROPHYTES IN LAKE-LADOGA -EFFECTS OF ENVIRONMENTAL-FACTORS

Littoral invertebrate communities (meio- and macrobenthos and zooplank ton) were studied in seven types of macrophyte associations commonly e ncountered in Lake Ladoga: in reed (Phragmites) beds on sand, soft and hard bottoms, in associations with the prevalence of Potamogeton spp. , Carex spp., and Equisetum fluviatile, and in diverse vegetation stan ds with e.g. Polygonum amphibium, Cicuta virosa, Typha latifolia and E leocharis acicularis. Some of the studied habitats were affected by se wage pollution, others were in comparatively undisturbed areas. Statis tically significant differences between invertebrate communities in th e different macrophyte associations were found. In stepwise multiple l inear regression analysis the following factors were identified as det erminants of abundance of aquatic invertebrates in macrophyte associat ions: shoot density, plant dry weight biomass, periphyton biomass, per iphyton chlorophyll a, periphyton primary production, and concentratio ns of Sr, Mg, Ca, P, Mn, Zn, Pb and Cu. Pollution was shown to have a minor effect on the composition of littoral invertebrate communities. It is not possible to determine one single principle factor responsibl e for the structure and density of invertebrates in macrophyte communi ties.