Seasonal production and molecular characterization of microcystins in Oneida Lake, New York, USA

Oneida Lake, northeast of Syracuse, New York, in the United States, is a shallow eutrophic lake with a well-established toxic cyanobacterial population. Samples for DNA, toxin, and phycological analyses were collected from six stations throughout the summers of 2002 (78 samples) and 2003 (95 samples). DNA was amplified by PCR using primer sets specific to the nonribosomal microcystin synthetase complex (mcyB and mcyD). PCR analysis in 2002 indicated that the microcystin genes were present in the water column from mid-June through October, as 88% of the samples tested positive for mcyB and 79% of the samples tested positive for mcyD. In both years the onset of microcystin production was detected as early as mid-July by the protein phosphatase inhibition assay, reaching a maximum in 2002 of 2.9 mu g L-1 and in 2003 of 3.4 mu g L-1. Beginning in mid- to late August of both years the microcystin level at all six stations was in excess of the World Health Organization (WHO) advisory level of 1.0 mu g L-1. In the present study we compared microcystin occurrence and potential production at the six stations using protein phosphatase inhibition assay, high-performance liquid chromatography, and polymerase chain reaction analyses. (c) 2005 Wiley Periodicals, Inc.