Ecology & Safety, Volume 8, 2014

Abstract: Allelopathic interactions of phytoplankton may cause the dominance of different species of algae and cyanobacteria which result in massive blooms in freshwater, brackish and marine ecosystems. Some species of microalgae are able to produce secondary metabolites that may be harmful to microorganisms, phyto and zooplankton, crustaceans, fish and even humans. In this study, the influence of allelochemicals on the growth and cell morphology of green alga Chlorella vulgaris was investigated by the addition of cell-free filtrate of Baltic cyanobacteria Nodularia spumigena and Synechococcus sp. cultures grown under 10 μmol photons·m-2s-1, 20 ºC and 8 psu. Harmfulness and toxicity of cyanobacterial cell-free filtrate was tested using Microtox 500, U.S Microbics Inc. These findings suggest that nitrogen-fixing N. spumigena and picocyanobacteria Synechococcus sp. can have negative influence on growth and cell morphology of tested green algae C. vulgaris and this effect was caused by released allelochemicals, which were nontoxic to bacteria Vibrio fischeri.