Spatial patterns of marine microorganisms and biogeochemical signatures along the Argentinian Beagle Channel during the austral winter (August 2017).

RODRIGUEZ-FLOREZ, C.; PACZKOWSKA, J.; FLORES-MELO, X.; MARTÍN, J.; GIL, M.N.; MALITS, A.

Conferencia; ASLO 2021 Aquatic Sciences Meeting; 2021

AGU

The microbial food web is nowadays recognized as a major driver of carbon and nutrient cycling in the sea. Marine microorganisms are fueled by dissolved organic carbon (DOC), whose origin and quality can be tracked by analyzing the optical properties of dissolved organic matter (DOM). The Beagle Channel is a subpolar marine environment influenced by terrestrial runoff and glacial meltwater with high seasonal and spatial variability. We herein present the first study of the microbial food web components in relation to biogeochemical signatures in the Argentinian Beagle Channel during austral winter. The study took place in a situation of vertical homogeneity to weak stratification of the water column and low chlorophyll a concentration (0.13±0.07 mg·m-3). Nonetheless, biogeochemical gradients are notable between the western (inner) and eastern (outer) parts of the study area, separated by the shallow sill at Mackinlay Strait. The bathymetry and basin morphology of the inner channel allows winter storage of nutrients and DOM that fuels the spring bloom. The specific UV absorbance of water (SUVA254, a proxy for the aromatic carbon content) and nitrate+nitrite are the main parameters affecting the microbial food web in surface-subsurface waters suggesting that prokaryotes were supported by allochthonous DOC derived from rivers discharges. Structural equation modeling relates nanoflagellates significantly to SUVA254 and prokaryotes suggesting an efficient microbial loop in surface-subsurface by channeling allochthonous DOC to higher trophic levels.