Screening for biological activities and toxicological effects of 63 phytoplankton species isolated from freshwater, marine and brackish water habitats

Several monitoring events in different freshwater, brackish water and marine habitats were conducted in the years 2004-2011. In some cases, mass occurrences of potential toxic species were accompanied by other species. While the antibacterial toxicity tests (LUMIStox) of samples showed the highest values, the producing taxa were not identified, although the bloom-forming species were in the majority. Under the acceptance that the accompanying taxa could be the source of the observed toxicity, we have tested 21 freshwater, 25 marine and 17 brackish water isolates for potential allelochemical production (e.g. alkaloids, flavonoids) and allelopathic activities (e.g. algicidal, antimicrobial). Most isolates accumulated potential phytochemical compounds in their biomass. Only polyunsaturated fatty acids, terpenes and sterols were found in supernatant extracts, but aldehydes, flavonoids, alkaloids and phenols were detected in biomass extracts. Of the bioassays employed in this study, the acetylcholinesterase inhibition test was the most responsive to the extracts, whereas the invertebrate lethality assay using Artemia salina was least sensitive. Standard tests for alkaloids, flavonoids, phenols including tannins and saponins indicate that bioactivities were not necessarily related to the presence of these compound classes. This indicates that other compound classes such as peptides/proteins or polysaccharides need also to be taken into consideration. These findings may have important consequences not only for ecological research but also for biotechnological applications. (C) 2012 Elsevier B.V. All rights reserved.