Effect of drifting macroalgae Cladophora glomerata on benthic community dynamics in the easternmost Baltic Sea

The present study focuses on dynamics of macroinvertebrate communities in shallow waters of northern coast of the Neva Estuary, Russia under eutrophication consequences such as proliferation of fast-growing filamentous algae Cladophora glomerata and oxygen depletion during the algae decomposition. Habitat characteristics (temperature, salinity, total phosphorus, and oxygen in water), taxonomical composition and abundance of zoobenthos were studied from May to October of 2003–2005. Temporary deoxygenation (0.6–2.8 mg cm− 3) of water near bottom caused by the decomposition of detached C. glomerata was recorded annually from July to August. At the same periods, abundance of macroinvertebrates decreased significantly, from 23.6 to 3.6 (2003), 51.9 to 0.4 (2004) and 34.9 to 1.4 thousand ind.m− 2 (2005). The coastal eutrophication in the Neva Estuary causes the destabilizing fluctuations in benthic abundance that can facilitate the shifts in littoral community structure.