Environmental Toxicology: Screening for Natural Toxins in Seafood  

Project Title: Environmental Toxicology: Screening for Natural Toxins in Seafood

Applicant: University of Hong Kong

Total Approved Grant: $120,000

Duration: 01/07/95 to 11/97

Project Status/Remarks: Completed

Scope: To find out the link between environmental pollution and presence of marine neurotoxins in locally consumed seafood.

Summary of the Findings/Outcomes: The study covered 4 major natural toxins in seafood. The major findings were :

(1) Paralytic Shellfish Poison : SPS was the most toxic among the natural marine toxins and was associated with redtide microplanktonic dinoflagellates. On sampling a number of local dinoflaellates, it was found that the toxic species belonged to Alexandrium, which lived in clean seawater. This species was very sensitive to salinity, temperature, pH and nutrients in the water. Peak occurrence for the toxin is Feb-Apr, with a minor peak in Sep-Oct. Over the past few years, the level of PSP contamination of local shellfish had been on the decline. The dinoflagellate synthesized the toxin during the night. Contaminated shellfish could convert the dinoflagellate toxins to other analogues, and could be depurated in clean seawater in 6-7 days.

(2) Ciguatera Poisons : This group of toxins were getting more common, and even relatively small fish had been shown to contain sufficient levels of the poison to cause clinical symptoms. Unfortunately their occurrence did not follow a set pattern - presumably owing to importation of marine fish from so many difference places including places where cigurtera were known to occur.

(3) Amnesic Shellfish Poison (domoic acid) : This toxin was known to be produced from diatoms (Pseudonitzchia), and had caused fatalities in North America. One species of this diatom occurred in abundance in Hong Kong. On developing a HPLC method to detect this toxin, the toxin in the local diatom was not found.

(4) Diuretic Shellfish Poison : This was the major toxin which contaminates shellfish in Europe. There was no definitive evidence of its occurrence in Hong Kong so far.