20 Nov 2021
20 Nov 2021
Status: this preprint is currently under review for the journal BG.

Acidification, deoxygenation, nutrient and biomasses decline in a warming Mediterranean Sea

Marco Reale1, Gianpiero Cossarini1, Paolo Lazzari1, Tomas Lovato2, Giorgio Bolzon1, Simona Masina2, Cosimo Solidoro1, and Stefano Salon1 Marco Reale et al.
  • 1National Institute of Oceanography and Applied Geophysics - OGS, Trieste, Italy
  • 2Fondazione Centro euro-Mediterraneo sui Cambiamenti Climatici, CMCC, Ocean Modeling and Data Assimilation Division, Bologna, Italy

Abstract. The projected warming, nutrient decline, changes in net primary production, deoxygenation and acidification of the global ocean will dramatically affect marine ecosystems during the 21st century. Here we assess the climate change-related impacts in the marine ecosystems of the Mediterranean Sea in the middle and at the end of the 21st century using high-resolution projections of the physical and biogeochemical state of the basin under the Representative Concentration Pathways (RCPs) 4.5 and 8.5. The analysis shows significant changes in the dissolved nutrient content of the euphotic and intermediate layers of the basin, net primary production, phytoplankton respiration and carbon stock (including phytoplankton, zooplankton, bacterial biomass and particulate organic matter). The projections also show a uniform surface and subsurface reduction in the oxygen concentration driven by the warming of the water column and by the increase in respiration. Moreover, we observe an acidification in the upper water column, linked to the increase in the dissolved inorganic carbon content of the water column due to CO2 absorption from the atmosphere and the increase in respiration. The projected changes are stronger in the eastern Mediterranean due to the limited influence, in that part of the basin, of the exchanges in the Strait of Gibraltar.

Marco Reale et al.

Status: final response (author comments only)

Comment types: AC – author | RC – referee | CC – community | EC – editor | CEC – chief editor | : Report abuse
  • RC1: 'Comment on bg-2021-301', Anonymous Referee #1, 09 Dec 2021
    • AC3: 'Reply on RC1', Marco Reale, 18 Feb 2022
  • RC2: 'Comment on bg-2021-301', Anonymous Referee #2, 13 Jan 2022
    • AC2: 'Reply on RC2', Marco Reale, 18 Feb 2022
  • EC1: 'Do not express pH changes in percent', Jean-Pierre Gattuso, 16 Feb 2022
    • AC1: 'Reply on EC1', Marco Reale, 18 Feb 2022

Marco Reale et al.

Marco Reale et al.


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Short summary
Mediterranean Sea ecosystems and their capability to provide ecosystem services are affected by several impacts related to human activities (e.g. overexploitation of marine resources and pollution). Future projections of the Mediterranean Sea biogeochemistry at the end of the 21st century, under two climate change emission scenarios, show an overall decline in the nutrient, oxygen and biomass content. The acidification trend is confirmed, and it is projected to be stronger in the Eastern part.