Alexandrium cysts (WHOI, D. Anderson)

This humpback whale died from saxitoxin which accumulated in the mackerel it was eating. (G. Early)

Closure signs such as these are posted when shellfish contains dangerously high levels of toxin. This image is from the massive 2005 New England red tide. (WHOI / J. Kleindinst)

Alexandrium stained with Calcafluor White (G. Usup)

A high concentration of Alexandrium cells. (D. Anderson)

Alexandrium cysts (WHOI, D. Anderson)

Calcafluor stained Alexandrium catenella, viewed under fluorescence. Photo by G. Usup