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BenthosAccording to S.V. Gerd (1946) 403 species and forms of bottom invertebrates dwell in Lake Ladoga. G.A. Stalmakova (1968) reports 385 bottom-dwelling macrobenthic organisms. Insect larvae (202 species) dominate the structure of macrozoobenthos. The number of species in other macrobenthic groups is smaller: worms - 66, water mites - 53, molluscs - 36, crustaceans - 18, other - 8. 203 species and forms of invertebrates were found in the meiobenthos of the lake: 13 species of Nematoda, 34 - Oligochaeta, 24 - Cyclopoida, 13 - Harpacticoida, 25 - Ostracoda, 8 - Tardigrada, 23 - Cladocera, 63 - Chironomidae. Thus, it is possible to conclude, that about 600 species of invertebrates dwell in the bottom biocenoses of Lake Ladoga. It should be specifically pointed out that glacial relict and marine-origin relict species live in Lake Ladoga: Pallasea quadrispinosa, Lamprodrilus isoporus, Amnicola steini, Pontoporeia affinis, Gammaracanthus loricatus lacustris, Mysis oculata relicta, Mesidothea entomon. The largest biomasses of the amphipod Pontoporeia affinis and the lumbriculid Lamprodrilus isoporus (8-9 g.m-2 and 1.0-1.5 g.m-2, respectively) were encountered in the least polluted areas with a depth from 15 to 52 m. The shallow zone is a zone of the highest productivity of benthic communities. The relative role of meiobenthos in the processes of energy transformation is highest in the shallow zone and decreases with depth. |
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