Cyanotoxins in two argentinian reservoirs. Bioaccumulation in tissues of O. bonariensis

AMÉ, MARÍA VALERIA; GALANTI, LUCAS NICOLÁS; RUIZ, MARCIA; MENONE, MIRTA; RUIBAL, ANA LAURA; RODRIGUEZ, MARÍA INÉS; GERPE, MARCELA; WUNDERLIN, DANIEL ALBERTO

Mar del Plata

Taller; IV Taller sobre Cianobacterias Toxígenas en Argentina, Bases para el desarrollo de herramientas para prevención y manejo de floraciones y para asegurar la calidad del recurso agua; 2010

FIBA

The occurrence of cyanobacterial toxic bloom is well known in several countries. However, a lack of information exists with respect to South America, with a small number of official reports and published data for the majority of countries. We evaluated the presence of four common microcystins (MC-LR, -RR, -YR and -LA) in water samples and tissues (liver and muscle) of Odontesthes bonariensis collected in Los Padres Lake (Buenos Aires). MCs were quantified by HPLC-ESI-MS/MS. The total content of MCs in water samples (2.8 ± 5.6 μg L-1) and in O. bonariensis muscle (3.9 ± 2.2 μg Kg-1) never surpassed guidelines values recommended by WHO for either recreational use of water or fish consumption. 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. In San Roque Reservoir (Córdoba), MC–LR, –RR and –YR and anatoxin-a were measured by HPLC-ESI-MS/MS in water samples. MCs y anatoxin-a were detected in 71% and 38% of the analyzed samples respectively. MCs higher levels were observed during summer while anatoxin-a higher amounts were found in Autumn. MC-RR and MC-LR showed similar frequency of occurrence but MC-RR reached the highest values. MC-YR was only found in 4 samples but during those blooms was the main cyanotoxin present. MCs levels showed positive correlation with Microcystis sp. biovolume (p<0,05, r=0,64), while anatoxin-a concentration showed similar results with Anabaena sp. biovolume (p<0,05, r=0,73). Comparison of MCs production under different environmental conditions showed that the dominance of toxic strains could be favored at 500 µg.L-1 of total inorganic nitrogen (TIN) and lower Chlorphyta composition of the phytoplankton. On the other hand, the dominance of anatoxin-a producing strains could be favored at higher pH and chlorophyll-a concentration, lower temperature and total phytoplankton biovolume and TIN close to 300 µg.L-1. As previously described for this reservoir, MCs levels surpassed guidelines values recommended by WHO for either recreational or drinking use of water. On the contrary, anatoxin-a levels are significantly below the guidelines established in New Zealand (6 μg L-1). Considering both spatial and temporal variability of cyanotoxin occurrence responsible authorities should consider the implementation of control measures to ensure that values remain within such limits of allowance. Furthermore, the persistence of different MC variants in fish muscle, even when these variant were absent in water samples, shows that further studies on the uptake and tissue distribution as well as evaluation on the transference of different MC congeners through the food web are necessary to fully understand and manage the presence of MC in freshwaters.