Huge Ceratium bloom in Plum Island Sound

This week our team collected an unusual dense mass of brown material in a 150u plankton net, towed near the mouth of Plum Island Sound. A quick look under the microscope confirmed reports of a huge harmless Ceratium bloom in the Gulf of Maine. Wow! Thanks to JC Weber for microscopy and photos.

Contents of cod end of a 150um mesh plankton net, looking almost like brown mud, held in a 1 liter plastic jar

Four isolated individuals of Ceratium

Microscope view of dense clumps of Ceratium and a couple of crab zoea in a gridded petri dish against a blue background

Closer view of a group of Ceratium, showing characteristic three horns and appearing white because the ethanol used to preserve this sample, intended for zooplankton identification, has leached out all the pigments. Individuals are about 200um long, judging by scale bar in lower right of photo