The biogeochemistry of major elements of the suspended particulate matter of the Cretan Sea

The biogeochemistry of the following elements Al, Fe, Si-bio, POC, PNtot, C a-bio, S-org, P and Mn has been studied within waters of the Cretan Sea in March and September 1994, as part of the PELAGOS project. Particulate alumi nosilicate concentrations, exemplified by Al, are very low (<1 mu gl(-1)) e specially in the upper waters. Higher concentrations occur below similar to 200 m, especially at depths of similar to 200 m and 500-700 m in the centr al and eastern areas, and are thought to result from sediment injections fr om the shelf edge and slope. The results for Si-bio, Ca-bio, P and S-org sh ow much higher concentrations within the photic waters. Temporal and spatia l high concentrations in these waters closely relate to the existence of cy clonic eddies on the east and west sides of the sea, while low concentratio ns are associated with an intervening anticyclonic eddy. However in Septemb er, discharge of Black Sea Water in the west sufficiently suppresses the th ermocline to prevent upwelled water from reaching the surface and hence the se substances are prevented from forming. Particulate Fe (expressed as Fe-excess) concentrations show much higher con centrations relative to Al in September, and are thought to result from add itional atmospheric inputs. The low particulate Mn concentrations in the up per water compared with deeper waters are considered to be a product of pho toinhibition of MnOx precipitation from Mn(II). An attempt has been made to assess input/output budgets of Al, Ca, Fe and M n through the Antikithira and Kassos Straits. Much of the outflows leave th rough the Kassos Strait and, except for Ca, net outflows through the Antiki thira Straits are negligible. (C) 2000 Elsevier Science Ltd. All rights res erved.