Atmospheric Deposition over the Aegean Sea and Its Impact on the Seawater Productivity

The role of the atmosphere as an external source of various nutrients and elements of both natural and anthropogenic origin in the Eastern Mediterranean and in particular the Aegean Sea has been investigated by using long-term deposition data collected ov

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Contents 1 Introduction 2 Methodology 2.1 Sampling Sites 2.2 Analytical Techniques 3 Results and Discussion 3.1 Atmospheric Deposition of Dust and Nutrients 3.2 Atmospheric Deposition Fluxes Versus Fluxes Through the Water Column 4 Conclusions References

Abstract The role of the atmosphere as an external source of various nutrients and elements of both natural and anthropogenic origin in the Eastern Mediterranean and in particular the Aegean Sea has been investigated by using long-term deposition data collected over a 21-year period at Finokalia, Crete, Greece. Dry deposition was

M. Tsagkaraki, C. Theodosi, and M. Kanakidou Environmental Chemical Processes Laboratory, Department of Chemistry, University of Crete, Heraklion, Greece e-mail: [email protected]; [email protected]; [email protected] N. Mihalopoulos (*) Environmental Chemical Processes Laboratory, Department of Chemistry, University of Crete, Heraklion, Greece Institute for Environmental Research and Sustainable Development, National Observatory of Athens, Athens, Greece e-mail: [email protected]; [email protected] Christos L. Anagnostou, Andrey G. Kostianoy, Ilias D. Mariolakos, Panayotis Panayotidis, Marina Soilemezidou, and Grigoris Tsaltas (eds.), The Aegean Sea Environment: The Natural System, Hdb Env Chem, DOI 10.1007/698_2020_679, © Springer Nature Switzerland AG 2020

M. Tsagkaraki et al.

found to be the main mechanism contributing 67% of total insoluble matter flux, 68% of total dissolved inorganic nitrogen (DIN) flux, and 75% of total dissolved inorganic P (DIP) flux. Sediment traps data from 200 sinking particulate matter samples collected at 2 different depths in the seawater column (500 m and 1715 m) in the Cretan Sea (southern Aegean Sea) during a 9-year period (1997–2005) were compared with atmospheric deposition data (simultaneously collected) to assess the role of atmospheric deposition on seawater productivity and mass transfer in the seawater column. Atmospheric deposition was found to play a significant role in seawater productivity of the Aegean Sea by providing essential nutrients and especially N in excess and by facilitating the creation of aggregates between atmospheric dust and biological material and thus influencing their mass transfer to deeper waters by increasing their size and settling velocity. Keywords Aegean Sea, Atmospheric deposition, Dust, Nutrients, Sediment traps, Lithogenic material

1 Introduction The atmosphere is a significant route by which both natural and anthropogenic compounds are transported from land-based sources to coastal and offshore waters [1–3]. This is of particular interest, especially for oligotrophic oceanic areas and semi-enclosed seas, such as the Mediterranean, due to the relative proximity of landbased sources and densely populated shores. Understanding the factors influencing the productivity of the basin is thus of paramount importance. It is well known that atmospheric deposition, especially in oligotrophic waters, could supply to the marine ecosystem most of the elements (N, P, Fe) necessa