Organic phosphorus in atmospheric deposition over the Mediterranean Sea: An important missing piece of the phosphorus cycle

Kalliopi Violaki (1) , François Bourrin (2) , Laurence Voutquenne-Nazabadioko (3) , Giorgos Kouvarakis (4) , Nicole Delsaut (5) , Nikos Mihalopoulos (4)

1 Environmental Chemistry Processes Laboratory, Department of Chemistry
2 CEFREM - Centre de Formation et de Recherche sur les Environnements Méditérranéens
3 OAS - Observatoire astronomique de Strasbourg
4 ECPL - Environmental Chemical Processes Laboratory [Heraklion]
5 CEFREM - Centre de formation et de recherche en environnement marin

To obtain a comprehensive picture of the spatial distribution of atmospheric phosphorus (P) speciation in the Mediterranean Sea, deposition samples were collected from the eastern (E) and northwestern (NW) Mediterranean and analyzed for both organic and inorganic P forms. Dissolved P, especially in organic form, is dominant during the wet season, while higher insoluble P fluxes are recorded during the dry period, mainly due to dust outbreaks. Wet deposition has a significant contribution to the atmospheric phosphorus flux; over the NW Mediterranean accounting for 80% of the total dissolved phosphorus (TDP). The seven-year average TDP flux during the wet season in the NW basin, of 1.78 mmol m −2 y −1 , is almost double that of the two-year average in the eastern Mediterranean. The difference is attributed mainly to the precipitation height being 2-3 times higher in the NW Mediterranean compared to the East. Dissolved organic phosphorus (DOP) is the dominant P fraction in both wet and dry deposition samples, presenting similar fluxes (1.16 and 0.94 mmol m −2 y −1 , in the eastern and northwestern basins respectively). Finally, assuming that all TDP is bioavailable, atmospheric deposition of TDP could account for up to 38% of new production in the eastern Mediterranean, while during oligotrophic periods of the NW Mediterranean it could increase the new production by 14%.

Domaines: Milieux et Changements globaux

Kalliopi Violaki, François Bourrin, Laurence Voutquenne-Nazabadioko, Giorgos Kouvarakis, Nicole Delsaut, et al.. Organic phosphorus in atmospheric deposition over the Mediterranean Sea: An important missing piece of the phosphorus cycle. Progress in Oceanography, 2018, 163, pp.50-58. ⟨hal-02042956⟩