2010 Peridinium quinquecorne Bloom in Southwest Florida (2010)

Peridinium quinquecorne is a type of alga called a dinoflagellate, a single-celled organism with two whiplike flagella that it uses to move through the water column. The organism can be found year-round in many brackish and estuarine waters in Florida. Peridinium quinquecorne can tolerate temperatures from 16 to 38ºC (60-100ºF) and survive in a wide range of salinities (11 to more than 32 parts per thousand). Peak concentrations occur shortly after rainfall heavy enough to cause surface runoff. When P. quinquecorne occurs at very high concentrations, called a bloom, it can discolor water red to brown. While P. quinquecorne does not produce toxins, it can cause fish kills by depleting the available dissolved oxygen in the surrounding waters.

Blooms of this organism have occurred alongshore of southwest Florida from late summer to early fall since 2005. In June 2010, several local fishermen in southern Lee and northern Collier counties reported discolored water. Water samples collected in these areas indicated a bloom of P. quinquecorne extending from southern Sanibel Island down to Seagate (see map at right). Several fish kills reported in association with this bloom continued through October 2010.