Pectenotoxin-2 and dinophysistoxin-1 in suspended and sedimenting organic matter in the Baltic Sea

Dinophysis acuminata, D. norvegica, and D. rotundata occur regularly in the Baltic Sea summer plankton. They are known to produce diarrhetic shellfish poisoning (DSP) toxins in coastal areas worldwide, but so far, evidence from the Baltic Sea is scarce, and the fate and transfer of their toxins in the ecosystem is poorly known. Occurrence of Dinophysis and DSP toxins was studied on the southwest coast of Finland in late July–September 2004 by sampling the water column down to the thermocline. DSP toxin profiles were analyzed using highperformance liquid chromatography–mass spectrometry from the thermocline sample from material collected with a sediment trap. Maximum abundances of D. acuminata (7,280 cells L21) and D. rotundata (880 cells L21) were above the thermocline, but D. norvegica (maximum 200 cells L21) was most abundant in the thermocline region. Pectenotoxin-2 (PTX-2) was found during the entire study period. Cellular PTX-2 content in Dinophysis varied between 1.6 and 19.9 pg PTX-2 cell21. Dinophysistoxin-1 (DTX-1) was found in samples after mid-August in concentrations ranging from 0.2 to 149 pg DTX-1 cell21. PTX-2 and DTX-1 were found in all sediment trap samples. The estimated sedimentation rate of PTX-2 was 0 to 15.4 ng m22 d21 and DTX-1 0 to 190 ng m22 d21, corresponding ,0.01% of PTX-2 and 1% of DTX-1 of the integrated water column DSP pool during a 6-week period. Sedimenting organic matter did not contain intact Dinophysis cells, but copepod fecal pellets found in the sediment traps indicated that fecal pellets are the major pathway of DSP toxins to the bottom. The major fraction of the PTX-2 and DTX-1 was either decomposed in the water column or transferred to higher trophic levels in the planktonic food chain. Harmful algal blooms are widespread phenomena in coastal areas of the oceans. Among harmful algal bloom events, diarrhetic shellfish poisoning (DSP) syndrome in humans is caused mainly by representatives of the genus Dinophysis (e.g., Yasumoto et al. 1985; Subba Rao et al. 1993) after ingestion of shellfish containing Dinophysis toxins. According to their chemical structure, the DSP toxins can be divided into (1) okadaic acid (OA) and its derivatives dinophysistoxins (DTX) (Murakami et al. 1982; Murata et al. 1982; Yasumoto et al. 1985), (2) pectenotoxins (PTX) (Yasumoto et al. 1985; Draisci et al. 1996, and references therein), and (3) yessotoxin (Murata et al. 1987). These toxins have been shown to cause acute gastrointestinal illness in humans, in addition to which they are cytotoxic, hepatotoxic, and tumor-promoting agents (Yasumoto et al. 1985; Van Egmont et al. 1993). Dinophysis acuminata Claparède et Lachmann 1859, Dinophysis norvegica Claparède et Lachmann 1859, and Dinophysis rotundata Claparède et Lachmann 1859 are common members of the summer plankton community in the entire Baltic Sea (Hällfors 2004). Dinophysis acuta Ehrenberg 1839 only occurs in the southern parts of the Baltic where salinities are higher. In the northern Baltic, 2 Present address: Finnish Environmental Institute, P.O. Box 140, FIN-00251 Helsinki, Finland. Acknowledgments We thank Tvärminne Zoological Station (University of Helsinki) for assistance and laboratory facilities, with special thanks to Ulla Sjölund, Torsten Sjölund, and Jari Långvik. Antti Räike is acknowledged for assistance with the map, and two anonymous reviewers for their criticism that greatly improved the article. This work was funded by the European Commission through the FATE project ‘‘Transfer and Fate of Harmful Algal Bloom (HAB) Toxins in European Marine Waters’’ (contract EVK3-CT2001-00055) as part of the EC-EUROHAB cluster. 1 Corresponding author ([email protected]). Limnol. Oceanogr., 51(5), 2006, 2300–2307 E 2006, by the American Society of Limnology and Oceanography, Inc.