A. A. Maximova, T. R. Ereminab, E. K. Langec, L. F. Litvinchuka, and O. B. Maximovad
a Zoological Institute, Russian Academy of Sciences, St. Petersburg, Russia
b Russian State Hydrometeorological University, St. Petersburg, Russia
c Atlantic Branch, Shirshov Institute of Oceanology, Russian Academy of Sciences, Kaliningrad, Russia
d State Research Institute of Lake and River Fisheries, St. Petersburg, Russia
e-mail: alexeymaximov@mail.ru
Received September 5, 2012; in final form, March 4, 2013
Abstract—The changes in the concentrations of the mineral nitrogen (nitrates and nitrites) and phosphorus and
in the state of the planktic communities in the eastern Gulf of Finland following a large-scale invasion of the
polychaete Marenzelleria arctia were analyzed. The bioirrigation and bioturbation of the bottom deposits by
polychaetes resulted in a dramatic increase in the nitrogen/phosphorus ratio in the waters of the gulf, thus lead-
ing to cascade changes in the plankton. As a result of the decrease in the abundance of colonial nitrogen-fixing
cyanobacteria, which cause “blooming” in surface waters, the total biomass of the phytoplankton and chloro-
phyll a concentration decreased. Because of the disappearance of large colonies of cyanobacteria and the surge
of small algae, the food supply for the zooplankton improved and its biomass increased. According to our cal-
culations, the amount of phosphorus deposited in the bottom sediments as a result of the polychaete activity
markedly exceeded the external phosphorus load on the Gulf of Finland from the Russian coast. We conclude
that the invasion of Marenzelleria arctia resulted in the cardinal reconstruction of the entire ecosystem of the
eastern Gulf of Finland.
DOI: 10.1134/S0001437013060052
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