HARMFUL ALGAL MONITORING IN BEAGLE CHANNEL, TIERRA DEL

HERNANDO M.; TORRES E.; SAN ROMÁN,N; HOFFMEYER, M. S

BIOCELL

Instituto de Histología y Embriología "Dr. Mario H. Burgos"

Lugar: Mendoza, Argentina; Año: 2007 p. 351 - 351

0327-9545

To determine the processes that favor the development of events of harmful algal blooms and their influence in mussel cultures, is being carried out a weekly monitoring of biological and oceanographic variables in Bay Brown (inside and outside) and Punta Paraná, Beagle Channel. These sites are closed to harvesting, generally during summer months, representing a serious problem for the health of consumers and the economy of the area. Results from phytoplankton indicated that the potential toxic species present are Alexandrium sp., Dinophysis sp. and Pseudo-nitzschia sp. Alexandrium sp. reaching 6000 cells/L during December of 2005 in the outside area of the Bay Brown. The values of toxins reached the 580 ug STX / 100 g. The increase in the number of toxic dinoflagelate was coincident with the maximum values of wind speed. Qualitative results from zooplankton for the same date revealed the presence of Drepanopus forcipatus and cypris larvae in all stations. Podon sp. was present only in Bay Brown whereas the Munida subrugosa zoeae although appeared in the three stations they were more abundant in Bay Brown (inside).. Oikopleura sp. also appeared in all the stations, being more abundant in Punta Paraná. A threshold of 1000 cells/L of Alexandrium sp was observed to overcome the 80 ug STX / 100 g. of mussel tissue, allowed for the human consumption. Starting from this such threshold in the phytoplankton until the detection of toxin in mussels, there was a lag time of 1-2 week. Low values of nitrite and nitrate was observed associated to the presence of high dinoflagelates biomass. A high percentage of zooplankton species observed are herbivorous which suggests a probable high grazing pressure on algal blooms, even during red tides.