Implementation and evaluation of monitoring of harmful algae and phycotoxins in a molluscs farm in Florianópolis - SC.

Abstract

Phytoplankton blooms are natural event and when it is associated with a harmful effect, they are called harmful algal bloom. Globally, the main syndromes caused by phycotoxins are PSP, DSP and ASP. This paper describes the results of the monitoring of the occurrence of harmful algae and phycotoxins at Ribeirão da Ilha, a mussel culturing area at Baia Sul/Florianópolis, southern Brazil, behind February and September of 2006.The occurrence of phycotoxins in Perna perna tissue was accessed by mouse bioassay and high performance liquid chromatography, while the presence of harmful species by light microscopy, from net and integral tube samples. The water temperature ranged form 17 to 28 ºC, the salinity from 32 to 35 ‰ and the transparency from 0.6 to 3.1 meters. Chlorophyll a varied from 1.1 to 5.9 mg m-3, characterizing this as a mesotrophic environment. Harmful species observed included Dinophysis acuminata and D. caudata in plankton net samples and P. minimum and some species of Pseudonitzschia at low counting, with a maximum of 7.2x103 and 4.6x104 cél.L-1, respectively. Samples were dominated by nontoxic algae, with an average of 3x105 cél.L-1, causing the observed negative results for toxin analysis and bioassays.