Acta Vet. Brno 2007, 76: 291-299

Effects of Different Oxygen Saturation on Activity of Complex Biomass and Aqueous Crude Extract of Cyanobacteria During Embryonal Development in Carp (Cyprinus carpio L.)

M. Palíková1, R. Krejčí2, K. Hilscherová3, B. Burýšková3, P. Babica3, S. Navrátil1, R. Kopp2, L. Bláha3

1Department of Veterinary Ecology and Environmental Protection, University of Veterinary and Pharmaceutical Sciences, Brno, Czech Republic
2Department of Fishery and Hydrobiology, Mendel University of Agriculture and Forestry in Brno, Czech Republic
3Center for Cyanobacteria and their Toxins (Institute of Botany, Czech Academy of Sciences; RECETOX, Masaryk University in Brno), Czech Republic

Received February 6, 2006
Accepted February 20, 2007

This study evaluates the effects of different oxygen concentrations on the toxicity of complex cyanobacterial biomass and aqueous extract of two cyanobacterial samples (prepared with regard to the content of the most studied cyanobacterial toxin microcystin: biomass 1 with the content of microcystins 2 560 μg l-1 of dry weight and biomass 2 with the content of microcystins 70 μg l-1 of dry weight, i.e. almost 37-times lower concentration) during embryonal development of carp (Cyprinus carpio). Effects of complex biomass and aqueous extract were tested at concentrations 120, 80 and 40 mg l-1 in four replicates, two of them aerated and two without aeration. The studied endpoints included the beginning and the end of embryo hatching, the presence of eye points at 48 h after fertilization, filling of air bladder, cumulative mortality and glutathione-S-transferase (GST) activities in surviving embryos. There was a significant increase in mortality in all variants without aeration after exposure to cyanobacterial biomass and aqueous extract (p < 0.01). The variants with aeration at greater cyanobacterial concentrations also lead to a significant mortality increase (p < 0.05). There was a decreased number of hatched embryos or no hatching at all in the non-aerated exposure variants for both biomasses. The lack of eye pigmentation 48 h after fertilization was observed at biomass concentrations of 120 and 80 mg l-1 for all non-aerated biomass exposures. There were fewer individuals with filled air bladder at the greatest tested concentrations of the complex biomass (biomass 1 and 2) and concentration of 80 mg l-1 (biomass 1) in the aerated variants. The activity of detoxification enzyme GST was studied during the experiment. GST activity was increased in treatments compared to control group in all aerated variants, but the changes were not always significant. The results of the conducted experiments clearly showed the important impact of oxygen saturation in water on the extent of cyanobacterial biomass toxicity. Mortality of fish eggs and embryos in experimental groups without aeration was significantly higher than in groups with aeration. Apart from the influence of toxic substances contained in the cyanobacterial biomass and the crude extract, oxygen deficiency affected the mortality in the groups without aeration.