Water and nutrient fluxes from major Mediterranean and Black Sea rivers: Past and future trends and their implications for the basin‐scale budgets

Abstract

[1] The aim of this study is to produce future scenarios on the river inputs of water and nutrients (nitrate and phosphate) into the Mediterranean and Black Sea. They are based on the four contrasting scenarios that were developed by the Millenium Ecosystem Assessment (MEA) for the years 2030 and 2050 and implemented in a spatially explicit manner into the IMAGE model. We first identified the major drivers of the river fluxes by regression analyses, then tested the retained models against the past evolutions between 1970 and 2000, and finally applied the models to the MEA scenarios. For nutrients, the considered river data mainly refer to the large rivers for which long-term time series exist (Rhone, Po, Ebro, and Danube). Here, recent trends were principally driven by fertilizer spreads (NO 3 , PO 4 ), together with urban wastewater releases (PO 4 ). Future trends remain in the envelope of the observed variability during the last 40 years, both for the large rivers and, when extrapolated to the basin scales, also for the entire Mediterranean and Black Sea. At regional scales, however, the budgets considerably change. In the northern parts of the Mediterranean drainage basin, they uniformly tend to decrease, but they may strongly increase in the south and east. Water discharge is examined on a basis of 37 rivers, showing that this parameter is clearly linked to the evolution of climate. Because of the ongoing evolution toward dryer and warmer conditions, we predict a significant trend of decreasing freshwater fluxes for the future, which already started in the past. Regional hot spots for this decrease are the drainage basin of the Alboran Sea and, when also considering the inhabitant specific water fluxes, the basins of the Aegean and north Levantine seas.

The CO<sub>2</sub> system in the Mediterranean Sea: a basin wide perspective

“…Ribera d 'Alcalà et al, 2003;Krom et al, 2005;Pujo-Pay et al, 2011). This fact along with the oligotrophic gradient from west to east could be attributed to the difference in the allochtonous nutrient sources in terms of quantity and quality (Ribera d'Alcalà et al, 2003;Ludwig et al, 2010;Schroeder et al, 2010;Krom et al, 2010) and also to the specific hydrodynamic features of the MedSea (Robinson et al, 2001;Millot and TaupierLetage, 2005;Huertas et al, 2012).…”

Holocene climate variability in the North-Western Mediterranean Sea (Gulf of Lions)

“…These compounds are primarily synthesized by higher plants and are constituents of epicuticular waxes of leaves. Their accumulation in the sediments of Gulf of Lions is primarily associated with the discharge and deposition of the Rhone River suspended particles in relation with precipitations (Ludwig et al, 2010). Figure 2a shows the temporal evolution of SSTs at the KSGC-31_GolHo-1B site over the past 10 000 years, including the post-industrial period.…”

Changes in the Adriatic oceanographic properties induced by the Eastern Mediterranean Transient

“…A number of authors attribute the gradient to the difference in the allochthonous nutrient sources in terms of quantity and quality (e.g. Ribera d 'Alcala et al, 2003;Ludwig et al, 2010), and to biogeochemical processes rather than to circulation itself (Crispi et al, 2001;Thingstad et al, 2005).…”