Abstract

Chile has an extensive estuarine system shaped by fjords and channels, characterized by a complex oceanographic dynamics. These fjords ecosystems play an important role in biological productivity and carbon cycles in aquatic ecosystems of the region. On the other hand, these fjords system are characterized by a wide variety of harmful microalgae blooms (HABs), which have some characteristic patterns of abundance and distribution in the area. Although some harmful microalgae species are recurrent in some geographical areas each year, their abundance during the productive spring-summer season in the Chilean fjords and estuaries varies locally and is determined by physical factors such as light, mixing, circulation patterns, salinity, temperature and chemical factors as nutrients availability. However, abnormal changes in these parameters may results in an increase in the occurrence, density, geographic coverage and distribution patterns of these harmful algae, as well as sporadic events of rare or less abundant algae species in the area, with serious consequences in coastal resources, local economy and public health. During the summer-autumn of 2016, different HABs affected fjords and channels of southern Chile, such as Alexandrium catenella and Alexandrium ostenfeldii, species associated with PSP production and Dinophysis acuta, Dinophysis acuminata and Protoceratium reticulatum, associated with the production of lipophilic toxins. This species showed important increases in densities and geographical coverage, unusual for the recorded data of these microalgae in the area, probably due to changes in weather conditions caused by strong ENSO event that affected the Pacific Ocean during the southern hemisphere summer.