LITTORAL-ZONE OF LAKE-LADOGA - ECOLOGICAL STATE EVALUATION

The littoral zone of a lake is an important ecotone between terrestria l and aquatic systems. From the point of view of the lake ecosystem, m uch of the mineral, organic and toxic substances entering the lake fro m the drainage basin are transformed in the littoral zone by physical processes and biochemical pathways. The littoral zone of Lake Ladoga c an be divided into three main regions: the shallow southern region, th e fairly steep western and eastern shorelines, and the northern archip elago. In these regions, the communities of aquatic macrophytes, perip hyton, phyto- and zooplankton and meio- and macrobenthos have been ext ensively studied. This paper presents numerical data on these communit ies, with special reference to comparisons between areas subjected to different degrees of anthropogenic loading. Most of the communities ar e characterized by high species diversity and spatial heterogeneity es pecially among the macrophyte associations in which intensive producti on and decomposition takes place. Water dynamics and water exchange ra te are the main abiotic factors in the formation of littoral communiti es. The characteristics of plant associations and bottom substrate, ra ther than pollution, appear as the most important factors structuring meio- and macrobenthic invertebrate communities in the littoral.