Major outputs of the recent multidisciplinary biogeochemical researches undertaken in the Aegean Sea

Abstract

The main outputs of a multidisciplinary and integrated studies are summarised. The results incorporate the latest biogeochemical researches, at basin scale, in the Aegean Sea (including thermohaline circulation studies, SPM dynamics, mass and energy fluxes, acknowledge biochemical processes in the euphotic and the benthic layer and benthic response to downward fluxes). The data were acquired within five (seasonal) research cruises, during 1997-1998. Data analysis and evaluation hence provided important new information on the functional processes of the Aegean ecosystem. In terms of water circulation, no new deep water formation in the Aegean Sea was observed, during 1997-1998, but rather intermediate water, due mainly to the mild winter conditions. All the biochemical parameters of the euphotic zone (nutrients, Particulate Organic Carbon (POC), chlorophyll-a, phytoplankton, primary and bacterial production), although high in the N. Aegean Sea reflect clearly the highly oligotrophic character of the Aegean Sea. In the N. Aegean, microbial food web was the main pathway of carbon, whereas in the S. Aegean, the food web could be classified as multivorous. An important Black Sea Water (BSW) signal was observed in the dissolved phase; this was especially pronounced in the Dissolved Organic Carbon (DOC), Mn and to a lesser degree to Cd, Cu and Ni concentrations. The downward material fluxes are higher in the N. Aegean, relative to the S. Aegean. Substantially higher values of near-bottom mass fluxes were measured in the deep basins of the N. Aegean, implying significant deep lateral fluxes of POM. The N. Aegean could be classified as a ''continental margin'' ecosystem, whilst the S. Aegean is a typical ''oceanic margin'' environment. There is a close relationship and, consequently, coupling between the near-bottom mass fluxes and the accumulation rates of organic matter (OM), with the near-bottom mineralisation, bioturbation, redox potential, oxygen consumption rates, the sediment microbiological and enzymatic activity and the meio-macro-and mega fauna abundances in the

Phytoplankton composition and abundance in the coastal waters of the Datça and Bozburun Peninsulas, south-eastern Aegean Sea (Turkey)

“…This feature is similar to the previous studies carried out in the Aegean Sea (Lykousis et al, 2002;Ignatiades et al, 2002). The low chl-a concentrations (<0.5 µg l -1…”

Assembling Ecological Pieces to Reconstruct the Conservation Puzzle of the Aegean Sea

“…This distinction is also reflected in the seawater circulation patterns, temperature, and productivity levels (Ignatiades et al, 2002;Lykousis et al, 2002;Zervakis et al, 2004). The S Aegean surface waters are characterized as more oligotrophic, as they are affected by the northward flowing, warm and high-salinity waters of the Levantine basin with minimum freshwater inputs from rivers; the N Aegean surface waters are more influenced by the cold, brackish Black Sea waters, and the nutrient-rich freshwater discharge of the major rivers draining southeastern Europe (Lykousis et al, 2002;Zervakis et al, 2004).…”

On the response of the Aegean Sea to climatic variability: a review

“…were the first to sketch the general circulation of the Aegean Sea, and Ovchinnikov (1966) produced maps of its seasonal variability. Since then, a large number of national and international studies have revealed the characteristics of the general circulation in more detail (Georgopoulos et al, 1989(Georgopoulos et al, , 1992Lascaratos, 1992;Theocharis et al, , 1999aZodiatis, 1993a,b;Zodiatis and Balopoulos, 1993;Stergiou et al, 1997;Balopoulos et al, 1999;Kontoyiannis et al, 1999;Tsimplis et al, 1999;Lykousis et al, 2002;Zervakis and Georgopoulos, 2002;Nittis et al, 2003). All studies agree on a cyclonic general circulation, with several sub-basin-scale permanent and recurrent eddies containing most of the kinetic energy.…”

“…The TMW mass enters the south Aegean through the Cretan Arc Straits to balance the outflow of surface and/or CDW. The thickness, salinity, dissolved oxygen and nutrient content of the TMW layer vary depending on the exchanges through the Cretan Arc Straits Theocharis et al, 1999a;Lykousis et al, 2002) and the corresponding residence time of that layer in the Cretan Sea. Longer residence times result in higher TMW salinity due to the enhanced action of vertical mixing with saltier layers (Boscolo and Bryden, 2001;Lykousis et al, 2002;Theocharis et al, 2002) relative to horizontal advection.…”