Over 36 Years of HAB Monitoring for the Aquaculture Industry: the Plancton Andino experience.

This study provides an overview of Plancton Andino’s Phytoplankton Monitoring Programme, with an emphasis on HABs over the past 30 years. Through the analysis of long-term data, changes in the frequency and monitoring efforts of HABs are highlighted. Notably, following the major Pseudochattonella cf. verruculosa and Alexandrium catenella blooms in 2016, there was an increase in sampling frequency. This shift introduces biases when comparing historical data, especially between pre- and post-2015 periods. For 2015–2025, we calculate the HABf INDEX, an algorithm incorporating HAB species, to assess HABs trends and associated risks for fish farming. Although the overall results indicate no increase in the HABf INDEX frequency within the marine inlets, species-specific patterns were observed: A. catenella showed a decrease in frequency, whereas Prorocentrum micans, Heterosigma akashiwo, and P. cf. verruculosa exhibited more frequent occurrences. These patterns are influenced by a combination of climate anomalies, such as reduced precipitation and freshwater inflows, eventual shifts in nutrient stoichiometry, particularly in southern Chile’s fjords and estuaries. Larger-scale events, like El Niño, can create conditions that are favourable for HAB development, though not consistently. Looking forward, we advocate for the integration of automated digital bio-imaging technologies with predictive numerical and machine learning models. Such advancements promise to enhance the responsiveness and effectiveness of HAB monitoring, providing tools to mitigate the social, economic, and environmental impacts of future events.