Persistent low concentrations of diarrhetic shellfish toxins in green mussels Perna viridis from the Johor Strait, Singapore: First record of diarrhetic shellfish toxins from South-East Asia

Abstract

Liquid chromatography-selected reaction monitoring mass spectrometry was used to identify and quantify Diarrhetic Shellfish Poisoning (DSP) toxins for the first time from tropical shellfish. Persistent, low concentrations of okadaic acid, 6 isomers of okadaic acid, and 5 isomers of dinophysistoxin-1 (DTX-1) were detected from green mussels Perna viridis from 3 sites in the Johor Strait, Singapore, between October 1995 and December 1997. Isomers of okadaic acid and DTX-1 generally occurred in higher concentrations than okadaic acid. The highest concentration of any single DSP toxin detected from Singapore shellfish was 97 ng g-1 mussel digestive tissue (wet weight) of an isomer of DTX-1 (DTX-1a). The maximum concentration of okadaic acid detected was 24 ng g-1 digestive tissue. These concentrations are well below the generally recommended limit for consumption of DSP toxins for humans (~1 μg toxin g-1 digestive tissue). Naturally contaminated mussels rapidly depurated okadaic acid when held in a laboratory aquarium; however, okadaic acid and some isomers of okadaic acid and DTX-1 could still be detected (