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2.2.3 Problems related to the presence and the types of the other pollutants in each country (heavy metals, escherichia coli)

In addition to natural biotoxins, anthropogenic pollution poses a serious threat to bivalve farming. Chemical pollution includes heavy metals (cadmium, lead, mercury) from industrial waste, and more recently, pollution related to microplastics and PFAS (perfluoroalkyl substances). However, the most daily and structurally impactful problem for the supply chain is microbiological pollution of fecal origin, traced by the indicator bacterium Escherichia coli. During heavy rainfall, overloaded sewer systems and agricultural runoff release enormous quantities of pathogens (including Salmonella, Norovirus, and Hepatitis A) into coastal ecosystems. The primary solution requires the use of purification centers (CDMs), where bivalves are kept for hours or days in tanks of constantly sterilized seawater (often by UV light or ozone) to purify themselves by filtering clean water before being released for sale.

Analyzing the context of partner countries, the challenges related to pollutants take on strong territorial connotations.

In Italy, the impact of anthropogenic pollution is a particularly sensitive issue, both for the lagoon areas of the North (such as the Po Delta and the Venice Lagoon, where agricultural and urban runoff causes frequent peaks of E. coli) and for the coastal areas of the South. An emblematic case at the European level is that of the Mar Piccolo of Taranto, in Puglia, a historic basin for mussel (Mytilus galloprovincialis) farming. Here, the proximity to heavy industrial hubs (steel and shipbuilding) has in the past caused serious problems with the bioaccumulation of persistent organic pollutants (such as dioxins and PCBs) and heavy metals in the tissues of bivalves. To protect public health, health authorities (ASL) have had to implement extremely stringent monitoring plans, sometimes prohibiting harvesting or requiring the transfer of juveniles to cleaner waters (Mar Grande) to complete the growth cycle safely.

In Spain, the driving force of aquaculture is concentrated in the Galician estuaries, extraordinarily productive yet vulnerable ecosystems. Despite the excellent water exchange provided by the Atlantic Ocean, strong human and urban pressure along the coasts requires constant monitoring of E. coli levels. This forces the sector to strictly classify production areas and make extensive use of purification centers. Moving to the Spanish Mediterranean coast (for example, in the Valencian Community), environmental studies highlight growing attention to the accumulation of heavy metals (such as lead and cadmium) in coastal sediments resulting from port traffic and historical discharges. Bivalves, acting as bioindicators, reflect this pollution, requiring monitoring to ensure that products remain well below the legal limits imposed by the EU.

In Greece, mussel farming is predominantly carried out in large, semi-enclosed gulfs in the north of the country, such as the Thermaikos Gulf. These areas benefit from the freshwater supply of large rivers (such as the Axios and Aliakmon), which is essential for feeding the bivalves. However, these same rivers carry the residues of intense inland agricultural activity to the sea, carrying pesticides, chemical fertilizers, and fecal bacterial burdens, especially during periods of heavy rainfall. Furthermore, in semi-enclosed basins, the problem of microplastics is emerging forcefully. Suspended mussels filter large quantities of microplastic particles (often resulting from the degradation of nets and plastic equipment used for farming, as well as from urban wastewater), raising new concerns both for the physiological well-being of the mollusc itself and for the chronic exposure of end consumers to these emerging contaminants. In France, bivalve farming (with a strong focus on oyster production) is often located in semi-enclosed basins, estuaries, or coastal lagoons (such as the Arcachon Basin in the Atlantic or the Étang de Thau in the Mediterranean), which are extremely vulnerable to human pressure. The most acute and recurring problem, particularly during the winter season and in conjunction with heavy rainfall, is norovirus contamination. Overloading the sewer systems of coastal municipalities frequently leads to the discharge of inadequately treated urban wastewater directly into production areas. Because traditional purification plants struggle to effectively eliminate viruses rather than bacteria, these contaminations force prefectures to impose frequent and sudden preventative harvest bans, causing immense economic damage to the sector, especially during peak consumption periods such as the Christmas holidays. Furthermore, agricultural runoff from vast inland watersheds contributes to nitrate and pesticide pollution, making integrated coastal water management a priority national challenge.

Despite boasting marine waters generally considered among the most pristine in Europe—a key commercial factor for export-oriented production of premium oysters—Ireland is not immune to these critical issues. Farming areas, mostly located in sheltered bays and loughs (fjords) along the rugged Atlantic coast, are sensitive to inputs from surrounding waterways. The intense and frequent rainfall typical of the Irish climate causes massive runoff, carrying agricultural fertilizer residues and livestock waste into the sea, as well as causing spills from local sewer systems and often undersized domestic septic tanks. This generates temporary peaks in microbiological contamination (Escherichia coli), which pose a constant threat to the health classification of production areas. Simply downgrading a bay from Class A to Class B forces breeders to bear the additional costs and logistical time required for stabling and the related passage through purification centers, significantly impacting profit margins and the competitiveness of companies.