Remote sensing, in-situ monitoring and planktonic toxin vectors of harmful algal events in the optically complex waters of the Galician rias (NW Spain)

Resumo

This thesis shows the capability of NN models to predict chlorophyll concentrations on the Galician coast from MERIS images following the widespread understanding of the need for regionally specific models. According to the recorded in situ data, the model presented here is an improvement on other previously used techniques, and made it possible to obtain reliable chlorophyll maps using almost every image. These maps were used to study the evolution of local oceanographic processes, which in turn were related to the development of algal blooms in the area. The present study allows more detailed examination of the chla distribution and detection of high biomass areas in the Galician rias and the adjacent area and should be an integral part of the monitoring programs. Moreover, the results of this study deduce that toxic events due to DA should be important concern and therefore DA in natural phytoplankton populations should be measured routinely in order to assess the potential of a DA outbreak. This is the first report about grazing rates of N. scintillans on Alexandrium cells. In addition, Noctiluca may inflict grazing pressure on the growth of PST species in the field, and could therefore play an important role as a regulator against PST-producing phytoplankton. The dynamic model showed that ingestion of toxic dinoflagellates by different types of planktonic organisms may be important for the dynamics of the toxins in the food web. However, both organisms illustrated a rapid (50 h) reduction of ingested toxin suggesting inefficiency to transfer toxins through predation in the food web.