Abstract

A twelve-month field survey of the genus Pseudo-nitzschia was carried out in Chinhae Bay, an area of commercial culturing and harvesting of oysters. The study used molecular DNA probes and WGA lectins to determine monthly species abundance and relate this to environmental conditions and nutrients. Ten species of Pseudo-nitzschia were identified during the study: Pseudo-nitzschia multiseries, P. pungens, P. multistriata, P. delicatissima, P. cuspidata, P. subfraudulenta, P. granii, P. fraudulenta, P. subpacifica, and an unidentified Pseudo- nitzschia sp. Of the Pseudo-nitzschia species, Pseudo-nitzschia pungens had the highest cell abundance, followed by P. delicatissima and P. multistriata. The presence of Pseudo-nitzschia multiseries was correlated with domoic acid (DA) contamination of shellfish, for example at Stations (Stn) P2, P3 and P4. Where Pseudo-nitzschia multiseries was recorded, trace levels of DA were detected, but at Stn P1 neither Pseudo-nitzschia multiseries nor DA were detected during the period of this study. Pseudo-nitzschia multiseries is regarded as the most toxic of the DA-producing species known in Korea. Korean isolates of Pseudo-nitzschia multiseries were strongly labeled by WGA lectin and the Pseudo-nitzschia multiseries species-specific DNA probe, and were distributed in seawater of lower temperature (≤ 15 °C) and linked with lower nutrient concentrations, although cell numbers were significantly lower than for Pseudo-nitzschia pungens. The use of the probes puD1, deD1 and frD1 led to the recognition of Pseudo-nitzschia pungens, P. delicatissima and P. fraudulenta, respectively. Although Pseudo-nitzschia species varied depending on month and sampling site, most were present at higher cell densities in lower temperature waters except for Pseudo-nitzschia multistriata. It was demonstrated that these methods provide a simple and rapid technique for the identification of a variety of Pseudo-nitzschia in Korean waters, and offer the opportunity for a series of real-time species detection in the future.