Characterization of dissolved organic matter and distribution of microbial food web in the San Jorge Gulf

JOANNA PACZKOWSKA; AUGUSTO C. CRESPI-ABRIL; FLAVIO E. PAPARAZZO; ANTONELLA DE CIAN; REGINA PIERATTINI; STEPHEN BRUGEL; ANDREW ANDERSON; RODRIGO J. GONÇALVES

Jornada; 8a Jornada de Becarixs CONICET-CENPAT; 2018

Organic matter (OM) is one of the largest reservoirs of organic carbon on the Earth, mainly produced by photosynthetic algae in the ocean. Around 10% of the total seawater OM is deliver to the ocean from external sources e.g. via rivers, or wet and dry deposition. OM is a major source of metabolic substrates to heterotrophic microorganisms and governs the production and composition of the microbial community. It is a complex mixture of low-molecular-weight (LMW) compounds such as amino acids, simple sugars and high-molecular-weight (HMW) represented by biopolymers e.g. proteins. LMW can be directly assimilated by heterotrophic bacteria while bigger molecular need to be transformed to more simple molecular through various enzymatic and abiotic (e.g., photolysis) processes. The aim of my study is to examine the source and composition of the dissolved organic matter in the San Jorge Gulf using absorbance and fluorescence spectroscopy. The Patagonian shelf region is a significant sink of atmospheric carbon dioxide (CO2) where the efficiency of the biological pump and thus the amount of the inorganic carbon fixed by photosynthetic organisms depends on phytoplankton composition and nutrients. The second part of my project is to study factors governing microbial community (phytoplankton, heterotrophic bacteria and nanoflagellates) and predict potential consequences of climate change on microbial food web in the San Jorge Gulf. Samples for my studies were collected during Pampa Azul campaign in October/November 2017.