Identification and quantification of the toxic dinoflagellate Gymnodinium sp. with competitive enzyme-linked immunosorbent assay (cELISA)

Polyclonal antibodies were raised against Gymnodinium sp. by immunizing rabbits with cells of the axenic strain. Based on the species-specific antiserum, an indirect competitive enzyme-linked immunosorbent assay (cELISA) was developed to identify and quantify Gymnodinium sp. A standard curve was established to correlate the cELISA signal to cell amount on a logit-log basis in the linear range between 24 and 6,250,000 cells, and the equation deducted was ln[A/(A0 − A)]= 4.9193 − 1.1006 log[cell amount] (R2 = 0.9948, n = 5). The detection limit was found to be 12 cells. The intra-assay and inter-assay coefficients of variation (CVs) were 5.8% and 9.7%, respectively. Field samples collected from Jiaozhou Bay, China were used to assess the robustness of the method. The results showed high agreement with that of cell-counting with a light microscope. The good reproducibility and precision of the cELISA implied that this new technique could be used for fast quantification of Gymnodinium sp.