Phytoplankton production and community respiration in different zones of the Curonian lagoon during the midsummer vegetation period

Abstract

1 - Phytoplankton structure, primary production, extracellular release of dissolved organic carbon and pelagic community respiration were investigated in different zones of the Curonian Lagoon in July 2002-2004. 2 - Phytoplankton biomass and primary production rates in different zones varied from 10.3 to 30.2 mg 1^-1 and from 530 to 2300 mg C m^-3 d^-1, respectively. Photosynthetic activity during the period of investigation on average was 2 times lower in the zone of seawater influence (Klaipeda Strait) than in the central part. 3 - The greatest differences in phytoplankton biomass and the rate of primary production in the investigated areas were registered during an intensive Aphanizomenon bloom. Total phytoplankton exudation ranged from 5 to 24% (on average 12%) of the total organic carbon production. 4 - The rates of production processes exceeded decomposition processes, thus stimulating the accumulation of autochthonic organic matter in the Curonian Lagoon during the midsummer vegetation period.