Bloom of Cochlodinium polykrikoides (Dinophyceae: Gymnodiniales) in Bahيa de La Paz, Gulf of California

As part of a continuing toxic microalgae monitoring program, phytoplankton samples were collected on 16–17 August 2012 at several sampling sites in the southern part of the Bahía de La Paz. A bloom of the dinoflagellate Cochlodinium polykrikoides was detected. Abundance of C. polykrikoides ranged from 73 to 276 × 103 cells L−1 on the first day to 980–1425 × 103 cells L−1 on the second day. Study of live specimens showed great variation in cell size and form, mainly as single cells or chains of two cells. Live cells were 30–47 μm long and 20–35 μm wide (n = 30). Seawater temperature during the bloom was 29–30 °C. Low densities of Cochlodinium convolutum, Cochlodinium helicoides, and Cochlodinium shuettii were also found in the samples of the bloom event. These high densities of C. polykrikoides did not lead to fish die-offs in the bay.