Marine and coastal pollution affects water, sediments, and biota. It can be related to oxygen-depleting substances, heavy metals, persistent organic pollutants (POPs), hydrocarbons, microorganisms, nutrients introduced by human activities or debris. The latter two sources of pollution are discussed in the chapters on Eutrophication and Marine Litter respectively. Many different kinds of pollutants enter the Mediterranean Sea from its shores (land-based sources) either via discharge points and dumping grounds (point-source pollution) or from surface fluvial run-off (non-point-source pollution). Pollutants also enter the marine and coastal environments through at- mospheric deposition, while others are introduced directly by marine activities such as shipping, fishing, mining, and oil and gas exploration.
Research on the impacts of pollutants on the environment has tended to focus on pollutants known to be most harmful to hu- man health (for example, mercury). The geographical distribu- tion of studies is poor, with little known about impacts from con- taminants in many regions of the Mediterranean.
Concentration, distribution and potential impacts of priority contaminants
Wastewater organic matter Organic matter in coastal and marine waters originates mostly from urban/domestic and industrial wastewater entering marine waters through direct point-source discharges or through rivers. The extent of organic matter pollution is measured as the Bio-
chemical Oxygen Demand (BOD), the amount of oxygen needed by microorganisms to oxidise organic matter in the water.
The distribution of coastal cities that either lack wastewater treatment facilities or have inadequate treatment facilities (de- fined as those removing less than 70 to 90 % of the BOD) can be used as a proxy to identify areas where potentially deleterious amounts of organic matter are being added to the marine en- vironment. Effective removal of pollutants from wastewater is achieved through secondary treatment that removes, through physical and biochemical processes, organic matter responsi- ble for 70 to 90 % of the BOD. About half of organic-matter pol- lution from sewage originates from direct, untreated discharg- es, while less than one-third is in discharges of inadequately treated sewage.
63 % of coastal settlements with more than 2.000 inhabitants operate a wastewater treatment plant, while 37 % do not. Sec- ondary treatment is mostly used (67 %) in Mediterranean treat- ment plants, while 18 % of the plants have only primary treat- ment (UNEP/MAP/MED POL and WHO 2010). The distribution of treatment plants is not uniform across the Mediterranean re- gion, with no sewage treatment in many cities on the southern shore of the Western Basin, in coastal Sicily, the Eastern coast of the Adriatic, the Aegean, and the northeastern corner of the Levantine Basin.
Organic-matter pollution in industrial wastewater was docu- mented by MED POL through an inventory of industrial point
HUMAN PRESSURE, STATE AND IMPACTS ON MEDITERRANEAN ECOSYSTEMS