The Mediterranean Sea, a unique semi-enclosed body of water nestled between Europe, Asia, and Africa, boasts a remarkably rich and diverse marine ecosystem. This basin, while covering less than 0.8% of the world’s ocean area, is recognized as a significant biodiversity hotspot. It supports an estimated 10,000 to 12,000 marine species, a notable proportion of which are found nowhere else on Earth. The sea encompasses a variety of habitats, including expansive underwater meadows, vibrant coral beds, and complex deep-sea features like hydrothermal vents and submarine canyons.
Marine Mammals
The Mediterranean Sea provides a habitat for a range of marine mammals, from agile dolphins to massive whales and seals. Several dolphin species inhabit these waters, including the common bottlenose dolphin, the striped dolphin, and the Risso’s dolphin, often observed near deep-sea canyons. Larger cetaceans also frequent the Mediterranean, with the fin whale being a regular presence.
Sperm whales, known for their immense size and deep-diving capabilities, are also found here, often in areas like the Hellenic Trench off Greece. These whales primarily hunt deep-sea cephalopods, particularly squids such as Histioteuthis bonnellii. Cuvier’s beaked whale, the only beaked whale species commonly found in the Mediterranean, prefers deep pelagic waters along continental slopes and near canyons.
The Mediterranean monk seal, considered one of the rarest pinniped species globally, has a population estimated between 815 and 997 individuals. Its population was reclassified from ‘Endangered’ to ‘Vulnerable’ by the IUCN in June 2023 due to signs of recovery. Historically, these seals rested on open beaches but now primarily use inaccessible sea caves for pupping and resting due to human disturbance.
Diverse Fish Populations
The Mediterranean Sea supports a vast array of fish species, contributing to its ecological and commercial value. Among the economically important species are the Atlantic bluefin tuna, sardines, anchovies, and hake. Bluefin tuna undertake extensive migrations, entering the Mediterranean through the Strait of Gibraltar in early spring to spawn, particularly around the Balearic Islands. Some adults remain residents year-round.
Beyond commercial species, the sea hosts diverse and visually striking fish. Groupers and barracudas patrol rocky reefs, while colorful parrotfish graze on algae. Various shark species, such as the sandbar shark and the common thresher shark, also inhabit these waters. The sandbar shark, a large coastal species, inhabits shallow coastal areas and preys on bony fishes, rays, crabs, and molluscs.
Invertebrate Wonders
The Mediterranean’s vibrant underwater world hosts a variety of invertebrates, forming the foundation of its ecosystems. Corals, such as the red coral (Corallium rubrum) and various gorgonians, create intricate underwater structures. Red coral, known for its striking color, grows on rocky seabeds in dark environments, typically at depths of 10 to 300 meters. Historically overexploited, populations are recovering in protected areas.
Sponges filter water, while various jellyfish species, including moon jellyfish and barrel jellyfish, drift through the water column. Crustaceans like lobsters, crabs, and shrimp scuttle across the seabed or hide in crevices. Mollusks, such as octopuses, squids, and numerous bivalves and gastropods, also thrive in diverse Mediterranean habitats, showcasing diverse forms and roles.
Reptiles and Seabirds
Marine reptiles and seabirds are integral to the Mediterranean’s fauna, using its waters for feeding, breeding, and migration. Prominent marine reptiles include the loggerhead (Caretta caretta) and green sea turtle (Chelonia mydas), with the leatherback (Dermochelys coriacea) as an occasional visitor.
Loggerhead turtles frequently nest along eastern Mediterranean coasts, particularly in Greece, Turkey, Libya, and Cyprus, with some nesting also occurring in Italy and Tunisia. These turtles primarily feed on sponges, crustaceans, and sea urchins. Green sea turtles nest in smaller numbers, mainly in Turkey, Cyprus, and Syria, consuming seagrass and seaweeds. Both species are migratory, with females returning to natal beaches to lay eggs.
Seabirds, such as the Audouin’s gull, Cory’s shearwater, and Yelkouan shearwater, forage across the Mediterranean. The Yelkouan shearwater breeds on coastal cliffs and islands in the central and eastern Mediterranean. These birds spend most of their lives at sea, returning to land only for breeding, and dive up to 45 meters to catch small pelagic prey like anchovy, sardine, and squid.