Chaetoceros pseudocurvesitus (light micrograph)
Chaetoceros is a single-cell organism belonging to the group of algae called diatoms. Diatoms are unique among phytoplankton in having a glasslike exterior made of silica. Chaetoceros forms chains and has long spinelike projections, called setae, to help it stay afloat in the water column. Large concentrations of Chaetoceros cells, called blooms, can discolor the water yellow to brown and cause fish kills by depleting dissolved oxygen or clogging the gills of fish. Chaetoceros does not produce a toxin. Chaetoceros can be found year-round in Florida’s waters, but blooms occur most often from winter to spring.