Variability of atmospheric deposition of dissolved nitrogen and phosphorus in the Mediterranean and possible link to the anomalous seawater N/P ratio

Atmospheric deposition of Total Dissolved Nitrogen (TDN) and Phosphorus (TDP) was studied in bulk deposition samples simultaneously collected at several locations around the Mediterranean, during one year period (June 2001-May 2002). Dissolved Inorganic Phosphorus (DIP) and Nitrogen (DIN) atmospheric deposition fluxes ranged from 243 to 608 mu mol m(-2)y(-1) and from 18.1 to 47.7 mmol m(-2)y(-1) respectively, presenting an important spatial variability within the basin. Wet deposition was found to be the main factor controlling DIN deposition in the Mediterranean. The amount of DIN deposited during the wet period was 2-8 times higher than that deposited during the dry season. It was estimated that about 65% of the total DIP was deposited during the wet period. Dust events as well as regional biomass burning were also found to contribute significantly to the DIP deposition. A significant percentage of the TDN and TDP of the samples were in organic form with Dissolved Organic Phosphorus (DOP) and Nitrogen (DON) accounting for 38% and 32% of TDP and TDN respectively. DIN/DIP molar ratio of the bulk deposition varied depending on the location of the sampling site in the Mediterranean basin, presenting an increasing trend from the Western (60) to the Eastern Mediterranean basin (105). This variation is similar to that observed in the seawater column, indicating an important link between atmospheric deposition and seawater productivity of the area. (C) 2008 Elsevier B.V. All rights reserved.