The role of the exchanges through the Strait of Gibraltar on the budget of elements in the Western Mediterranean Sea: consequences of human-induced modifications.

The role of the Strait of Gibraltar on the exchanges of substances between Mediterranean Sea and the Atlantic Ocean is reviewed. The previous estimations have been recalculated by using a similar water flux and compared with the river and atmospheric inputs to the Western Mediterranean Sea. The man-induced changes in the dimensions of the Strait of Gibraltar increasing (planning the sill) or reducing of the cross-section by a total or partial dam are discussed. A total dam will control the sea-level rise in the Mediterranean Sea, but an annual increase of major nutrient concentrations of 1-2% could be expected, lower than the rate of increase of the river and atmospheric inputs in the Western Mediterranean Sea. The increase of the cross-section of the Strait by increasing the depth (planning) at the sill could compensate the increase of the external nutrient inputs.