The Unique Features of the Ionian Sea due to the presence of the Hellenic Trench
The Hellenic Trench is a 1100 km long bathymetric feature that runs parallel to the western, southern and south-eastern coasts of Greece. It extends from the North of Lefkada island to the southeastern part of Crete and consists of a series of linear trenches and small troughs in which the depth increases steeply.
The 1000m contour is typically within 3-10 km of the closest island or mainland coast. The hadal zone of the Hellenic trench is roughly 4,150 metres (13,615 feet) to 5,300 metres (17,388 feet) deep. This region constitutes an area of critical habitat for the endangered Mediterranean sperm whale, whose population only numbers a few hundred individuals at best. The waters of the trench are very low in nutrients, and that presents a paradox; the largest predator thriving in the most oligotrophic (poor in nutrients) sea in the world. The answer to this paradox is that the prey of sperm whales, which consists almost exclusively of deep-living squid (sperm whales can dive up to 1000m deep) is not related to the productivity of water at the surface.The Hellenic Trench is also an important habitat for Cuvier’s beaked whale, another particularly vulnerable species. The bottlenose dolphin, striped dolphin, common dolphin and Risso’s dolphin also exist there. This is an area which ACCOBAMS has proposed should be designated as an Area of Special Importance/Marine Protected Area because of its cetacean populations.