Relevance of sporadic upwelling events on primary productivity: The key role of nitrogen in a gulf of SW Atlantic Ocean

PAPARAZZO, FLAVIO E.; PIERATTINI MARTÍNEZ REGINA; ELENA FABRO; RODRIGO J.GONÇALVES; AUGUSTO CÉSAR CRESPI-ABRIL; GASPAR SORIA; BARBIERI, ELENA S.; ALMANDOZ, GASTÓN O.

ESTUARINE COASTAL AND SHELF SCIENCE

ACADEMIC PRESS LTD-ELSEVIER SCIENCE LTD

Lugar: Amsterdam; Año: 2021 vol. 249

0272-7714

Inorder to assess the relevance of sporadic upwelling events on primaryproductivity, the availability of nitrogen (N) sources and their uptake byphytoplankton were studied. Incubations of 15N-enriched samples were performed at3 depths in 12 stations in San Jorge Gulf (SJG, Patagonia Argentina) aboard ofthe R/V ?Puerto Deseado? during November 2016. Additional coastal stations weresampled to analyze the upwelling event. The total uptake of N sources (ρNO3- +ρNH4+) was higher on the surface than in the deep layer. The ρNO3- by phytoplanktondoubled that of ρNH4+ suggesting SJG acted as a CO2 sink during the periodstudied. However, NH4+ played an important role in maintaining primaryproductivity where NO3􀀀 was low. In most stations, phytoplankton showeda preference for the uptake of the less available N source, likely resultingfrom adaptation to low nutrient concentrations. However, in the southwesternsector of the gulf, where a wind-induced upwelling occurred, phytoplanktonpreferred to uptake NO3􀀀 , this being the most abundant N source. As aconsequence, the integrated primary productivity in the water column of thatsector was high. Results suggest that such high productivity was governed bythe optimal relationship between the preference and availability of N,established by the presence of elevated NO3􀀀 and low NH4+ ambient concentration. This wouldbe a physiological process regardless of community composition. The new primaryproductivity generated by upwelling events could be key to feeding thebiological resources of the gulf