Poster Session 1, Monday,  October  3, 15:40–18:00

Poster 65

Impacts of extreme events on phytoplankton phenology and blooms

The southern and south regions are among Brazil’s most important economic areas, comprising the most productive artisanal and industrial fisheries, nourished by Plata River outflow and upwelling regions, in addition to harboring enormous marine biodiversity with more than 65 protected areas. Phytoplankton phenological indices are key indicators for the characterization of marine ecosystems. Thus, this work aims to determine the phenological indices and their relationship with bloom events from the last 23 years (1999 to 2022) and their response front of extreme events associated with climate change in this important marine ecosystem. The remote sensing compilation of daily, 4 Km resolution chlorophyll data from Copernicus GlobColour database was used to determine the phytoplankton phenological indices and blooms events. We used the cumulative sum of chlorophyll anomalies to calculate the indices and the threshold of the 90th percentile to calculate the bloom events. The continental shelf showed the most prolonged high chlorophyll periods and more notable differences in upwelling and nutrient regions with the influence of river outflow currents. In those regions, the bloom period started early in the year and finished later than in the surrounding areas. Those same regions showed pronounced differences between the two analyzed decades, with a noticeable increase in duration, intensity, frequency, and bloom events in the last decade. The slope and rise of the Brazilian continental margin presented more homogenous phenological indices, with an average duration of 160 days, showing latitudinal differences, lasting less in the northernmost portion and longer in the southernmost part.

*Ligia Luz, Center of Marine Biology – University of São Paulo, [email protected]

Áurea Maria Ciotti, University of São Paulo, [email protected]

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