Mussel culture and the accumulation of domoic acid.

The cultured mussel industry of Prince Edward Island had never experienced a toxic disease problem until November of 1987. With the successful use of the long-line culture system, the yearly production of fresh mussels to the gourmet food market had risen to close to 3.2 million pounds (1.46 million kg) of product. The physiology of this sessile bivalve and its method of feeding and location in the estuary leave it prone to the accumulation of a widely distributed biotoxin. Eastern Prince Edward Island became the epicentre of domoic acid-intoxicated mussels as early as 10 November 1987 (retrospective samples) during an intense bloom of the diatom Nitzschia. Mussels were able to accumulate large amounts of the domoic acid with little effect on their own well-being. Despite being in low water temperatures (below 4 degrees C) and under thick ice cover, the levels of the toxin decreased and were undetectable in about 6 weeks. The following year the toxin was detected in much smaller amounts, and the levels of toxin accumulation demonstrated a variable lag time with the increase in concentration of Nitzschia available in the water column. The sales of Prince Edward Island cultured mussels have rebounded to about 140% of the pre-domoic acid crisis.