Factors shaping microbial community structure and dissolved organic matter composition during austral spring in the San Jorge Gulf

PACZKOWASKA, JOANNA; PAPARAZZO, FLAVIO; AUGUSTO CÉSAR CRESPI ABRIL; PISONI, JUAN PABLO; GABRIELA NOEMI WILLIAMS; DE CIAN, ANTONELA

bremen

Congreso; International Conference for Young Marine Researchers; 2021

Marine biological productivity depends on phytoplankton and heterotrophic bacterialinteractions, influencing the energy and carbon transfer to higher trophic levels includingfish, birds and marine mammals. The aim of this project was to study major factorsgoverning the microbial food web and dissolved organic matter characterization in the SanJorge Gulf, the largest basin of the Patagonian Shelf. San José Gulf campaign was carriedout during austral spring 2017. Surface water samples were collected for biological(chlorophyll a, microbial abundances) and chemical analyses (dissolved inorganicnutrients, colored dissolved organic matter (CDOM), humic substances). Moreover, theSimpson stability parameter was calculated to estimate water mixing condition based onCTD data. A clear district of the stratified waters observed mostly in the central part of theGulf from the well-mixed coastal areas was observed. Stratified waters were characterizedby higher small phytoplankton (pico- and nanophytoplankton), heterotrophic bacteria,nanoflagellates abundances and the relative contribution of protein-like (C1) compound.Lower temperature and higher wind speed observed in southern coastal area extendingover the South Bank and southern edge of the Gulf contributed to well mixed waterconditions likely supporting larger phytoplankton cells growth. Additionally, higherbiological index (BIX), the relative contribution of humic-like (C4) compound and humicsubstance concentrations were recorded. Northern coastal waters were characterized byhigher salinity, the relative contribution of humic-like (C2, C3) compounds and humificationindex (HIX).