Thermaikos Gulf

The Thermaikos Gulf, the largest gulf in the Aegean Sea, stretches from Thessaloniki to Larissa in the west and to Chalkidiki in the east. It is a semi-enclosed and relatively shallow marine area, with a maximum depth of 45 m and a width ranging from 5 km in the northern part to 50 km in the southern part. The Gulf includes an extensive system of river estuaries, salt marshes, lagoons, and salt pans, which constitute important habitats for wildlife and provide multiple ecosystem services.

Four major rivers flow into the Thermaikos Gulf – Axios, Loudias, Aliakmonas, and Gallikos – forming one of the most important wetland complexes in Greece. This complex includes the Kalohori lagoon, the estuary of the Gallikos River, the delta and riverbed of Axios, the delta of Aliakmonas, the Nea Agathoupoli wetland, and the Kitros salt pan.

The area is protected under the Natura 2000 Network and the Ramsar Convention, while most of it has been designated as a National Park. The National Park covers an area of 338 km² and includes 17 habitat types, two of which are Priority Habitats. The combination of wetlands, agricultural lands, meadows, and sand dunes creates a mosaic of highly valuable habitats, located close to the urban center of Thessaloniki.

The Thermaikos Gulf is one of the most important biodiversity areas in the country, hosting more than 370 plant species, 299 bird species, 50 mammal species, 27 amphibian and reptile species, over 50 fish species, and 65 invertebrate species. The area has global ornithological significance, as it lies along one of Europe’s main migratory routes.

In the Axios–Loudias–Aliakmonas Delta, 66% of Greece’s bird species have been recorded, including significant populations of rare species such as the Dalmatian pelican, avocet, sandpiper, night heron, and little bittern. The area also hosts a range of mammals, from small insectivores to larger species such as otters and water buffalo, as well as large populations of reptiles and amphibians, including the largest populations of Mediterranean tortoises in Europe.

Despite its high ecological value, the area has been significantly impacted by human activities, including river diversion and dam construction, drainage networks, pollution from agricultural, industrial, and urban sources, as well as unauthorized development. Pollution from the Axios River, which is a transboundary issue, heavily affects the Thermaikos Gulf.

Additionally, the Thermaikos Gulf is the largest mussel farming area in Greece. Intensive mussel farming generates significant amounts of waste, mainly plastic nets, which constitute one of the main sources of marine pollution in the area.