Re: Do you know why dinoflagellates produce toxins?

Hi:

This is a very interesting question... I used to grow these dinoflagellates, and
have wondered the same thing.  An obvious reason would be to kill the things
that eat them (a single Alexandrium cell is capable of killing a tiny larval
fish!) But there may be more prosaic, subtle reasons. I recently heard that a
diatom toxin, domoic acid, may be produced as a way to get rid of extra
photosynthetic energy (producing more sugar than they need may be a bad idea,
perhaps because they leak the sugar, and this attracts bacteria).  

In the case of some dinoflagellates, the toxin contains lots of N nitrogen
(i.e., the PSP, paralytic shellfish poisoning species such as Alexandrium, that
contain saxitoxins).  You may find information at the HAB (red tide) homepage at
the Woods Hole Oceanographic website (here).  Other toxins are C and
O rich (cyclic poly-ethers, a chain of rings, like the Olympic emblem, only
longer). Maybe that dumping of excess photosythetic function would explain them.
This is mostly still a mystery, though.

Cheers,
Dean Jacobson, College of the Marshall Islands