[bradleyjg]

It depends on whether or not they bioaccumulate^W -- checking wikipedia apparently the word I want is biomagnification.

The basic idea is that as you move up the food chain the concentration of toxins gets higher. So a plant might have a relatively low level of toxin absorbed even if it was directly applied, but a shellfish that consumed algae that were exposed to the toxin downstream from the farm might have a considerably higher level.

I don't know a whole lot about the details in this specific case, but that's my concern.