Bloom of Pyrodinium bahamense var. compressum at the Southern region of the Mexican Pacific

A bloom of Pyrodinium bahamense var. compressum was registered in Acapulco Bay (Guerrero, Mexico) from July 7 th to August 4 th 2010. This bloom started in the state of Oaxaca (towards the East). The HAB didnt cause water discoloration, possibly because the highest densities were from 3 to 5 m below the surface. Heavy rains were present before the event. The longest chains had 16 cells, with a mean of 8 cells; occasionally bigger and less compressed single cells were found. Among the dinoflagellates, Pyrodinium was dominant (88%), although few Prorocentrum (P. gracile, P. triestinum ) and also some naked dinoflagellates ( Karenia sp., Gymnodinium catenatum and Gyrodinium fusus ) were found. The highest Pyrodinium cell densities (1.4. 10 6 cell l -1 ) were from outside the Bay; inside the Bay the cell densities were 7.7. 10 5 cell l -1 at 3 m depth and 5.2. 10 5 cell l -1 at 5 m. Small diatoms were present; Pseudo-nitzchia spp. were important reaching densities of 14.0 10 3 cell l -1 . Saxitoxin concentration reached values of 2092 µg STX eq. 100 g -1 in violet oyster ( Chama mexicana ) near Puerto