Microcystin-LR, -RR, -YR and -LA in water samples and fishes from a shallow lake in Argentina

We evaluated the presence of four common microcystins (MC-LP, -RR, -YR and -LA) in water samples and tissues (liver and muscle) of Odontesthes bonariensis collected in Los Padres Lake (Argentina). MCs were quantified by HPLC-ESI-MS/MS. The total content of MCs in water samples (2.8 +/- 5.6 mu g L-1) and in O. bonariensis muscle (3.9 +/- 2.2 mu g kg(-1)) never surpassed guidelines values recommended by WHO for either recreational use of water or fish consumption. The total content of MCs in O. bonariensis liver was 33.6 +/- 37.2 mu g kg(-1). However, we observed both spatial and temporal changes in MC profile, suggesting the need of an intensive monitoring program at such lake to ensure the health of people living in its surrounding. We observed a significant correlation between the content of total and dissolved MC in water and the concentration of these toxins in liver, showing the probable uptake of dissolved MC by O. bonariensis. MC-RR was the dominant variant in water samples, followed by MC-LA and MC-LR. MC-YR was always present in water samples, but in the lowest concentrations of the congeners measured. MC content in liver in O. bonariensis was ten-fold higher than the corresponding content in fish muscle. However, MCs were present in muscle of O. bonariensis during both wet and dry season, while we could not detect MCs in liver during the dry season. These results demonstrate that MC accumulation in liver and muscle of O. bonariensis occurred with different profiles. Moreover, different uptake, tissue distribution and excretion pathways may occur between diverse MC variants. For instance, during the dry season, an increase in the relative percentage of MC-LR in water samples was accompanied with an augmentation in the relative percentage of this toxin in muscle of O. bonariensis. Conversely, a rise in the relative percentage of MC-LA in water samples during the dry season did not impact on the distribution of this toxin in fish muscle. These results suggest the need of further studies on dynamics of different variants of MC to pursuit a complete evaluation of human health risk associated to MC occurrence. (C) 2009 Elsevier B.V. All rights reserved.