US EPA

1135115 

Journal Article 

ALLELOPATHIC EFFECT OF FRESHWATER CYANOBACTERIA SPECIES ON THE GREEN ALGA, Ankistrodesmus falcatus 

Vasconcelos, V; Almeida, L 

2008 

1 

Fresenius Environmental Bulletin
ISSN: 1018-4619
EISSN: 1610-2304 

Parlar Scientific Publications 

17 

9A 

1264-1269 

English 

WOS:000260802000010 

In this work we studied the inhibitory effects on the growth of the green alga Ankistrodesmus falcatus due to the compounds of several strains of freshwater cyanobac-teria (Microcystis aeruginosa and Planktothrix planctonica). Strains producing and non producing microcystins were used and the toxicity of fractionated extracts and also of the water soluble compounds released to the medium was tested. Raw extracts of the different cyanobacteria strains and five fractions (water soluble fraction, 20%, 50%, 80% and 100% methanol) were used. Extracts were placed in test tubes corresponding to cell densities of 10 super(4), 10 super(5), 10 super(6), 10 super(7) cells/ml. A. falcutus was then inoculated to a final density of 10 super(4) cells/ml. Results showed differential responses to the different cyanobacteria strains. The growth inhibition is not related to microcystins at least during acute exposures. Hydrophilic compounds may be released to the water at very low cyanobacteria densities causing inhibition effects while the bloom is in its early development. Massive populations of cyanobacteria may men release more lipo-philic substances that inhibit phytoplankton. 

allelopathy; cyanobacteria; green algae; Ankistrodesmus falcatus