Density, biomass, and distribution of benthic invertebrates in the mid-lake zone of the coastal Lake Gardno

The mean density (4.2 × 103 ind. m-2) and mean biomass (10.8 g wet weight m-2) of the mid-lake zoobenthos in the mixo-oligohaline Lake Gardno were consistent with the respective ranges typical of freshwater, polymictic, and strongly poly-trophic lakes of northern Poland. The major components of the Lake Gardno macrozoobenthos were tubificid oligochaetes and chironomid larvae, the latter dominating in terms of abundance and biomass. Neomysis integer (Leach) was the sole and numerically scant marine invertebrate in the Gardno mid-lake macro-zoobenthos. Biodiversity, taxonomic composition, dominance structure as well as densities and biomass of the macrozoobenthos studied showed considerable spatial variation. The lake-river contact zone exhibited the presence of the ecotone effect. Dynamics of the abundance and biomass of the benthic invertebrates inhabiting that zone were markedly different from those found in other mid-lake habitats of the Gardno.