View across the Outer Harbour of Stornoway

Thursday 9 April 2009

Paralytic shellfish poisoning

I was asked on Twitter this morning which website issues warnings for paralytic shellfish poisoning (PSP). This danger involves shellfish (bivalve molluscs), which ingest algae from the seawater. The toxins contained in the algae accumulates in the shellfish and can accumulate to dangerous levels. Each week, samples are taken from waters around Scotland and Northern Ireland and are assayed using a method called HPLC for the presence of the toxins. The results are published here.

It is worth bearing in mind that algae are plants, and using sunlight and photosynthesis for their energy requirement. Therefore, algal blooms will occur mostly in summer with their attendant risk of PSP. They are becoming an increasing problem, due to pollution like run-off of fertiliser from the land into the sea.

If PSP levels reach the warning level, local authorities will issue a press release specifying which area has been closed to shellfish harvesting. As far as I can tell, Comhairle nan Eilean Siar issued such a prohibition in 2006 on Loch Roag - a major shellfish harvesting area.

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