Pelagic primary production in the coastal Mediterranean Sea: variability, trends, and contribution to basin-scale budgets

• Published in: Biogeosciences
• Main Authors: Salgado-Hernanz, Paula Maria, Regaudie-de-Gioux, Aurore, Antoine, David, Basterretxea, Gotzon
• Format: Article in Journal/Newspaper
• Language: English
• Published: Copernicus Publications 2022
• Subjects: article; Verlagsveröffentlichung; North Atlantic; North Atlantic oscillation
• Online Access: https://doi.org/10.5194/bg-19-47-2022; https://noa.gwlb.de/receive/cop_mods_00059771; https://noa.gwlb.de/servlets/MCRFileNodeServlet/cop_derivate_00059420/bg-19-47-2022.pdf; https://bg.copernicus.org/articles/19/47/2022/bg-19-47-2022.pdf

We estimated pelagic primary production (PP) in the coastal (<200 m depth) Mediterranean Sea from satellite-borne data, its contribution to basin-scale carbon fixation, its variability, and long-term trends during the period 2002–2016. Annual coastal PP was estimated at 0.041 Gt C, which approximately represents 12 % of total carbon fixation in the Mediterranean Sea. About 51 % of this production occurs in the eastern basin, whereas the western and Adriatic shelves contribute with ∼25 % each of total coastal production. Strong regional variability is revealed in coastal PP, from high-production areas (>300 g C m−2) associated with major river discharges to less productive provinces (<50 g C m−2) located in the southeastern Mediterranean. PP variability in the Mediterranean Sea is dominated by interannual variations, but a notable basin-scale decline (17 %) has been observed since 2012 concurring with a period of increasing sea surface temperatures in the Mediterranean Sea and positive North Atlantic Oscillation and Mediterranean Oscillation climate indices. Long-term trends in PP reveal slight declines in most coastal areas (−0.05 to −0.1 g C m−2 per decade) except in the Adriatic where PP increases at +0.1 g C m−2 per decade. Regionalization of coastal waters based on PP seasonal patterns reveals the importance of river effluents in determining PP in coastal waters that can regionally increase up to 5-fold. Our study provides insight into the contribution of coastal waters to basin-scale carbon balances in the Mediterranean Sea while highlighting the importance of the different temporal and spatial scales of variability.