Author(s): Esperanza Cea-Martinez; Carolina Meruane; Alberto De La Fuente
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Abstract: The southern coast of Chileis a unique region with a complex marine system of fjords and channels. Despite this region is almost uninhabited, it has been affected by harmful algal blooms (HABs) events, which have increased in frequency and extension during the last decades. As an example, during the summer of2016, under El Ni~no conditions, an explosive red tide bloom occurred with important socio-environmental consequences. The aim of this study was to characterize with field observation and remote sensing the environmental conditions during different harmful algal blooms events, in order to stablish the bases of heuristic approach for predicting HAB events. For doing this, we first studied the 2016 event and postulated three hypotheses that later on were evaluated with other HABs events: 1) the occurrence of storms and the subsequent increase of fresh water inflow, bring favorable conditions to microalgae blooms, due to nutrients transport from the continent to the coast; 2) the occurrence of storms and the subsequent increase in wind speed cause vertical mixing of the surface layer with the deeper one, thus allowing the nutrients transport from deep waters; 3) the events of HABs in this coastal area develop predominantly in years of El Ni~no. We checked these hypotheses thorough analyzing past historical conditions during other HABs events. The results indicated that there is a relation between the occurrence of storms events with the increase of chlorophyll-a, thus validating the first and second hypothesis, although further study and measurements are required to identify the relative importance of each forcing. Regarding to the third hypothesis, it was found that is not entirely correct, rather it can be said that algae blooms develop mostly in years of transition to El Ni~no or under this phenomenon, in which the sea surface temperature is higher than the historical average.
Year: 2018