Large diatom bloom off the Antarctic Peninsula during cool conditions associated with the 2015/2016 El Niño
Raul Rodrigo Costa, Carlos Rafael Borges Mendes, Afonso Ferreira, Virgínia Maria Tavano, Tiago S. Dotto, Eduardo R. Secchi
Abstract
Abstract Diatoms play crucial functions in trophic structure and biogeochemical cycles. Due to poleward warming, there has been a substantial decrease in diatom biomass, especially in Antarctic regions that experience strong physical changes. Here we analyze the phytoplankton contents of water samples collected in the spring/summer of 2015/2016 off the North Antarctic Peninsula during the extreme El Niño event and compare them with corresponding satellite chlorophyll- a data. The results suggest a close link between large diatom blooms, upper ocean physical structures and sea ice cover, as a consequence of the El Niño effects. We observed massive concentrations (up to 40 mg m –3 of in situ chlorophyll- a ) of diatoms coupled with substantially colder atmospheric and oceanic temperatures and high mean salinity values associated with a lower input of meltwater. We hypothesize that increased meltwater concentration due to continued atmospheric and oceanic warming trends will lead to diatom blooms becoming more episodic and spatially/temporally restricted.