Occurrence of potentially toxic and harmful thecate dinoflagellates in mussel farms at Penha municipality.
The purpose of this study was to describe the composition and occurrence of potentially toxic and harmful species of thecate dinoflagellates in cultured shellfish, located at Armação do Itapocorói (AI) and Praia Alegre (PA) in the municipality of Penha, SC-Brazil. Water samples were collected and environmental parameters (salinity, water temperature and depth of Secchi disk) were determined weekly between April 2007 and April 2008 at two sites by a monitoring program maintained by the Laboratory for the Study of Harmful Algae, CTTMar, UNIVALI. The identification of the organisms was made through an Olympus microscope, model BX41 with up to 1000×. During the sampling period, we identified 21 species of thecate dinoflagellates potentially toxic and harmful in the genus Alexandrium, Ceratium, Dinophysis and Prorocentrum. The species P. obtusum (86%), D. acuminata (78.5%) and P. micans (72%) were very frequent throughout the period in the two sample points. The point with highest species richness was the AI, with 14 species, and the PA had the lowest richness with only two species. Most samples were considered rare relative to the abundance of thecate dinoflagellates compared to the presence of harmful microalgae, but during the month of September 2007, were considered abundant, during which there was a bloom of D. acuminata. The similarity between the two points throughout the sampling period reached a high coefficient (86%), and between the months examined, June 2007 showed the lowest similarity (10%) and July 2007 the greatest similarity recorded (91%). The composition and distribution of thecate dinoflagellates during the study showed that the existence of a dynamic community structure could be used as a tool to aid the monitoring of harmful algae mariculture activity in this region.