Macrophyte vegetation as a structuring factor of the macrozoobenthic communities in Lake Ohrid

The macrophyte communities in Lake Ohrid have a key role in general maintaining of the lake’s metabolism. They are particularly important for the distribution and structuring of rich benthic macroinvertebrate assemblages, in as much as they provide a constant stream of oxygen, are an important source of food and serve as shelter from predators. A survey at six sites along the coastal zone of Lake Ohrid was conducted in order to determine the role of macrophyte communities in structuring of the macrozoobenthos inhabiting the littoral zone of the lake. With respect to species composition, the results point to the Gastropoda, with 23 registered taxa, as the most diverse among the seven groups of benthic fauna. The second most diverse was the group of Insecta with 11 species, followed by Hirudinea and Oligochaeta with seven species, while six species from Crustacea were registered. The lowest biodiversity was registered for Bivalvia and Turbellaria – three species from each group. It was also found that mixed stands of Charophyta with other macrophytes where Charophyta species predominate represent the most attractive habitats, being inhabited by 54 species, versus homogenous stands of Chara tomentosa, where 36 species were registered. The most abundant species were Dreissena presbensis and Radix relicta, which reached their maximum densities on homogenous stands of Chara tomentos