sources of pollution in 2003. The areas with the highest BOD are the southern shore of the Western Basin, the eastern coast of the Adriatic, the Aegean and the northeastern sector of the Levantine Basin. These regions, in general, also have insufficient sewage wastewater treatment facilities. This indicates that there is likely a cumulative effect of elevated organic matter in coastal waters from a combination of domestic and industrial sources (UNEP/MAP 2012). In the northern Mediterranean BOD is mainly released by wastewater treatment plants and the food industry, while in south and eastern Mediterranean other sectors like oil refining, farming of animals, textiles, paper or fertilisers are im- portant emitters (UNEP/MAP/MED POL 2012).

For marine animal and plant communities, oxygen depletion caused by either human-induced eutrophication or by input of organic matter in wastewater may be fatal. Addition of organic matter and eutrophication (resulting from productivity increas- ing because of the extra supply of nutrients) often stem from the

same sources and act together to deplete oxygen. See the Eu- trophication chapter for further discussion.

Oxygen is reduced by organic matter carried by wastewater through two processes. First, the increase in particle concentra- tion reduces light penetration in water, reducing the depth of the zone in which photosynthesis occurs. The net effect is a re- duction in the release of oxygen from the water column. Second- ly, introduced organic matter uses up oxygen as it decomposes, especially near the bottom where particulate organic matter set- tles. In the Mediterranean, many instances of fish and shellfish kills have been recorded, as these species are the first to be af- fected by oxygen limitation.

Benthic communities are among the first to disappear under conditions of heavy stress. Benthic organisms play an impor- tant ecological role by reworking the sediments, which affects the flux of nutrients across the sediment-water interface. Thus

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STATE OF THE MEDITERRANEAN MARINE AND COASTAL ENVIRONMENT