The general characteristics and distribution of zoobenthos in the southern part of the Gulf of Riga | Общая характеристика и вопросы распределения зообентоса в южной части Рижского залива

The species composition of zoobenthos in the southern part of the Gulf of Riga (Baltic Sea) is described. Data on the density and biomass of zoobenthos as well as on its vertical distribution in different depth zones are presented. It was established that in the studied area 97.1 % of the total zoobenthos is composed by four crustacean species: Pontoporeia affinis, P. femorata, Heterocyprideis sorbyana, Paracyprideis fennica, the mollusc Macoma baltica and a group of oligochaetes. 96.3 % of the total zoobenthos biomass is composed by three crustacean species - Mesidothea entomon, P. affinis and P. femorata and two mollusc species - M. baltica and M. edulis. In the zoobenthos of the considered area the glacial relicts compose more than 87% by abundance and about 57% by weight. In general, the zoobenthos of the southern Gulf of Riga is of poor species composition. The density of individuals in the bottom fauna is high but their total biomass rather low. Differently from other areas of the Gulf of Riga where zoobenthos is the best developed in the coastal zone, in the considered area zoobenthos is the best developed at moderate depths. It is characteristic that the number of mass species is low and the glacial relicts are in majority both by the abundance and by weight. It has been established that the ferromanganese concretions do not have negative influence on the quantitative development of zoobenthos.

Published

Not Known