Seasonal Potentially Toxic Species Dynamics and the relation with oceanographic variables in Extreme Southern South America (Beagle Channel, Argentina)

HERNANDO, M.; ALMANDOZ G. O.; MONTOYA, N.; FERRARIO, M. E.

Gyeongnam

Congreso; 15th Internacional Conference on Harmful Algae; 2012

The occurrence of HABs is a recognized problem for shellfish aquaculture in the Beagle Channel, where there is an extensive historical record of PSP events. To determine the processes that induce the development of HAB and their influence in shellfish cultures, a weekly monitoring of biological and oceanographic variables has been carried out in the Almanza region of the Beagle Channel between July 2005 and November 2007. A total of 10 potentially toxic species were found: Alexandrium catenella, A. ostenfeldii, A. tamarense, Dinophysis acuminata, D. rotundata, Prorocentrum cordatum, Pseudo-nitzschia australis, P. cf. calliantha, P. fraudulenta and P. cf. seriata. Peak densities of A. catenella, D. acuminata and P. cf. calliantha were within the ranges of abundances from which toxin accumulation in shellfish is usually observed in other regions. The presence of A. catenella and A. ostenfeldii coincided with PSP detection in mussels (up to 580 µg STXeq 100 g-1). Likewise, neoSTX, STX and N-sulfocarbamoyl (C). toxins were determined by HPLC from net samples, coinciding with the predominance of A. ostenfeldii. The increase in the number of toxic dinoflagelates was related to the highest wind speed values. A threshold of 1000 cells l-1 of Alexandrium sp. was observed to be needed to exceed the regulatory limit of 80 µg STXeq 100 g-1 of shellfish tissue. Based on this threshold a lag time of 1-2 weeks was observed before the detection of toxins in shellfish. Low values of nitrite and nitrate were associated with the presence of high dinoflagelates biomass.