Occurrence of toxic cyanobacterial blooms in San Roque reservoir (Córdoba - Argentina): a field and chemometric study .

AMÉ, MARÍA VALERIA; DIAZ, MARÍA DEL PILAR; WU NDERLIN, DANIEL ALBERTO

ENVIRONMENTAL TOXICOLOGY

Wiley

Lugar: Adelaida, Australia; Año: 2003 vol. 18 p. 192 - 201

1520-4081

We have evaluated the presence of cyanobacteria blooms in San Roque reservoir (Córdoba - Argentina). Cyanobacterial blooms and water samples were collected over 4 years (1998-2002). We confirmed the presence of microcystin-LR and microcystin-RR in 97% of these blooms. The total amount of microcystin (MC) ranged between 5.8-2400.0 g·g-1 of freeze-dried bloom material. These values suggest that guidelines for safe water consumption and recreational use should be established for this reservoir. Twenty-eight physical and chemical parameters were measured in water samples and evaluated by discriminant analysis (DA). A first DA was used to evaluate the factors promoting cyanobacteria occurrence, identifying 9 parameters following three different patterns associated with cyanobacterial growth. Inorganic phosphorous was found to promote the presence of blooms, whereas the highest proliferation of cyanobacteria was observed in the presence of smaller amounts of carbonate, bicarbonate, sulphate and faecal coliform bacteria. The results observed during our fieldwork, analyzed using DA, agreed with other laboratory studies, thus confirming the usefulness of DA to achieve conclusions from a complicated environmental data matrix. A second DA, using only water samples collected during the presence of cyanobacteria blooms, identified another 9 parameters. The analysis of these parameters allowed us to identify certain environmental factors that could lead to the dominance of toxic strains, thus increasing the amount of MC. The results showed that, in our case, an increase in the water temperature was associated with higher amounts of MC per dry weight unit, whereas an increase in the concentration of N-ammonia and Iron were associated with lower amounts of MC, thus disfavoring the dominance of toxic strains.