The diatom Pseudo-nitzschia australis is another alga that releases toxins when digested. That's often the way science progresses. New research leads to new questions, and for awhile the problem gets fuzzier, not clearer. Then the pieces finally come together and it all makes sense. At this point, about the only thing all the scientists studying marine toxins agree upon is that the problem is serious, and lots of work needs to be done.
Some scientists insist the problem is growing.
Others look at the same evidence and say we're just looking harder and finding it in places where we hadn't looked before. Others see blooms where there's no significant pollution. That was thought to have been the case off Northern Carolina a few years ago, but scientists later determined that the algae had been transported from Florida to North Carolina by a purely natural phenomenon, the Gulf Stream. It's very difficult to study. Other species kill without toxins, such as this Chaetoceros species with its serrated spines that can lodge in fish gills.