So…does red tide affect shellfish? Filter feeding shellfish like clams, mussels,
and scallops accumulate phytoplankton toxins as they feed.
Up until several years ago, we were told that humans were affected by red tide
but the shellfish themselves were not.
However, Laurie Connell, a researcher at UMO, is part of a group of scientists
that have found that clams can suffer many of the same symptoms as humans do.
Some clams can become lethargic or lie in the mud with their necks hanging out
if there are lots of toxic phytoplankton around. Other clams become resistant
to red tide toxins. These clams come from areas that have historically had a
lot of red tide blooms. Because of their resistance, they are less affected
physically from red tide toxins and can feed longer. They may accumulate greater
levels of the red tide toxins because of this, take longer to flush toxins out
after the bloom is over, and therefore be unfit for human consumption for a
longer period of time.