Acta Univ Latv (2008) 745: 63–74

Influence of inorganic nutrients and dissolved organic matter on the growth of cyanobacteria Microcystis aeruginosa isolated from the Gulf of Riga

Abstract

The influence of nutrient additions in N-limiting, P-limiting and in DIN:DIP-balanced conditions with and without dissolved organic matter (DOM) of land origin was studied on the growth and toxin content of Microcystis aeruginosa isolated from the Gulf of Riga. The dissolved inorganic nitrogen (DIN) and dissolved inorganic phosphorus (DIP) supply in balanced ratio of DIN : DIP = 16 is the main determinative factor for M. aeruginosa development, promoting increases in cell biomass, chlorophyll a content and particulate organic matter. In medium enriched only by DOM, M. aeruginosa used 31 % of the available dissolved organic nitrogen and 53 % of the dissolved organic phosphorus. The experiment conditions did not invoke increment of toxicity. The experiments showed that the development of M. aeruginosa is promoted by the raised load of inorganic nutrients and dissolved organic matter to the brackish ecosystems of the Baltic Sea.