(Barcelona, Cartagena and Malaga). In the Adriatic Sea, high lev- els of lead have been recorded in biota in the Venice lagoon and in the areas affected by the Po River discharges (consistent with the distribution pattern of urban and industrial discharges), the Gulf of Trieste, Vlora Bay and close to Durres. In general, the dis- tribution of elevated lead levels in biota is correlated with the distribution of discharges and non-point sources of pollution from mining, industry and sewage.
Mercury levels are high in sediments around Messina, Palermo and Reggio Calabria in Sicily, potentially influenced by natural contributions from volcanic and geothermal sources of the southern Tyrrhenian Sea. Mercury sediment anomalies in some islands of this region may also be explained by proximity to volcanic and geothermal sources of mercury. Elevated levels of mercury have also been recorded in sediments in the Po Delta region, the Gulf of Trieste, the Aegean Turkish coast and Israel (e.g., Haifa Bay). High mercury concentrations were measured in biota along the northwest Italian coast (Gulf of Genoa, Por- toscuso, Palermo), the coastal waters of the Tyrrhenian Sea (es- pecially between Fiumicino and Naples and around Messina), Skikda (Algeria), Cartagena (Spain) and at Kastela Bay (near Split) on the western Adriatic coast. Significant concentrations of cadmium have been reported in sediments along the coast of France (Marseille-Fos), Spain (Cartagena), Morocco (Tangier- Martil and Nador), in the northeastern corner of the Levantine Basin between Cyprus and Turkey (including Iskenderun Bay) and the northern coast of Syria. In biota, relatively high levels of cadmium were recorded in biota at sites along the southern and southeastern coasts of Spain (Cabo de Gata, Almeria, and Cartagena), an intensely mined region, and at a few sites along the western coast of Italy (Naples), the southern shores of the Tyrrhenian Sea (Messina and Palermo), western Sardinia and France (Sete and Nice). In the Adriatic, high levels of cadmium are found in biota in the Po Delta and in Kastela and Rijeka bays (Croatia), due to the discharge of untreated urban and indus- trial wastewaters. Scattered samples of organisms in the Cen- tral and Eastern Levantine basins allow identification of some sites with high concentrations of cadmium in biota. Cadmium is also elevated in biota along the western coast of Turkey (Izmir Bay), Piraeus (near Athens) in the Aegean Sea and in Vlora Bay (Albania) in the Adriatic.
Despite the work of the MED POL programme, short time series and differences among sampling conditions mean that most available pollution data for the Mediterranean are not yet ad- equate for robust trend analysis (UNEP/MAP/MED POL 2011). Preliminary analyses show mixed trends. For example, data from Haifa (Israel) and the Gulf of Lions (France) indicate that heavy metals in sediments are declining, while no change is ob- served in mercury concentrations in the Gulf of Trieste, despite the closure of mining in Idrija (Slovenia).
Trends in heavy metals in biota were examined at sites with data for periods of at least five years starting in the late 1990s. These analyses showed that, while trends at individual sites tended not to be significant, there was a general pattern of stable to de- clining trends. A few stations with high levels of metals in biota in the Western Mediterranean (e.g., Marseille, Fos and Pombino) and in the Adriatic (e.g., Rijeka and Kastela bays in Croatia and Durres and Vlora Bay in Albania) showed slightly increasing trends. By contrast, Naples, Genoa and Bizerta Lagoon (Tunisia) showed decreasing trends. Additionally, in several cases there
46 STATE OF THE MEDITERRANEAN MARINE AND COASTAL ENVIRONMENT
was an apparent decline of outlier values, such as in locations in Italy, which may reflect a general improvement in areas with particularly high levels of metal pollution.
The exposure of marine and coastal organisms to elevated con- centrations of heavy metals exacerbates the ecological stress they are regularly subjected to by natural stressors, such as temperature and salinity fluctuations. The presence of toxic sub- stances in the marine environment, even at low levels, will give rise to biochemical reactions that may cause stress to marine or- ganisms. Among the results of prolonged stress is the suppres- sion of the immune system, increasing susceptibility to infection. Although new techniques measuring the total response of or- ganisms to all possible stressors have been developed, none of them can give accurate estimates of levels of acute or sublethal toxicity of contaminants. Sensitive in situ bioassays are needed to measure water and sediment toxicity using indigenous organ- isms (UNEP/MAP/MED POL 2005).
Mercury is a highly toxic element that is found in elevated con- centrations in Mediterranean marine biota. Studies conducted in the 70’s in pelagic fish but also recent studies revealed that Hg concentrations in Mediterranean fish are twice those found in the same species living in the Atlantic Ocean. The presence of cinnabar deposits and volcanoes in the Mediterranean, as well as the anthropogenic emissions from various land based sources, are the possible Hg sources, which are transported to the marine environment through river and point land based emissions, as well as through atmospheric precipitation (Cossa and Coquery, 2005). Risks to Mediterranean ecosystems also stem from the ef- fects of cadmium on top predators and from lead on predators of shellfish (UNEP/MAP/MED POL 2005).
Persistent Organic Pollutants (POPs) Persistent organic pollutants (POPs) are organic compounds that are resistant to environmental degradation through chem- ical, biological, and photolytic processes. POPs persist in the environment, are capable of long-range transport, bioaccumu- late in human and animal tissue, biomagnify in food chains, and have potentially significant impacts on human health and the environment. POPs include certain chlorinated pesticides and industrial chemicals such as polychlorinated biphenyls (PCBs), most of which have already been prohibited in Mediterranean countries. However, POPs can also be unintentionally released, mainly as a result of combustion processes or as by-products in some industrial processes. Some examples are dioxins and furans, hexachlorobenzene (HCB), PCBs, or polycyclic aromatic hydrocarbons (PAHs).
The MED POL NBB inventory report (UNEP/MAP/MED POL 2012) states that in the Mediterranean, very high levels have been historically measured in the marine environment, espe- cially in top predators and cetaceans. However, a general de- crease of POPs concentrations has been observed over the last years, although in some cases concentrations still remain rela- tively elevated.
The inventory includes very few reports for the already pro- hibited organochlorines, which confirms that they are no longer released from industrial point sources. HCB and PCBs are mostly released as unwanted by-products in the cement and metal industry, while chlorinated pesticides are emitted by the organic chemical industry, or by wastewater treatment
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