The Mediterranean Sea harbors diverse and ecologically important coral populations. These corals, distinct from their tropical counterparts, form intricate underwater structures that support a wide array of marine life.
Unique Characteristics and Diversity
Mediterranean corals differ from tropical corals. Many species, especially in deeper waters, do not host symbiotic algae and thus do not rely on sunlight for nutrition. Instead, they are filter feeders, capturing microscopic organisms and particles from the water column. This adaptation allows them to thrive in dimly lit environments, such as caves and deep rocky bottoms, ranging from 10 to several hundred meters deep.
The diversity of Mediterranean corals includes both hard and soft coral types. Hard corals, like Corallium rubrum (red coral), form rigid, calcified skeletons that create complex, tree-like structures. Red coral is notable for its slow growth, sometimes less than a millimeter per year, and its long lifespan, with colonies potentially living for centuries. Other species include the yellow coral (Dendrophyllia ramea) and various gorgonians, such as the red gorgonian (Paramuricea clavata), which form fan-shaped or arborescent colonies. These species contribute to unique bio-constructions known as coralligenous habitats.
Ecological Importance
Mediterranean corals play a fundamental role in the marine environment, acting as biodiversity hotspots despite not forming extensive coral reefs like those in tropical regions. These corals create complex, three-dimensional habitats that provide shelter, feeding grounds, and nurseries for a wide variety of other marine species. Over 1,300 marine species, including various fish, crustaceans, and sponges, depend on these coral habitats for their survival.
The intricate structures formed by coral colonies and coralligenous ecosystems enhance the overall marine biodiversity of the Mediterranean Sea. They contribute to sediment stabilization and oxygen production, supporting rich flora and fauna. Deep-sea corals in the Mediterranean can support more marine life than areas without coral, with up to 25% of regional marine species relying on these systems.
Major Threats
Mediterranean coral populations face threats from human activities and climate change. Marine heatwaves, with high sea temperatures sustained for days or weeks, have caused mass mortality events, depleting coral populations by 80% to 90% in some areas. The Mediterranean Sea is warming faster than the global ocean average, exacerbating these impacts. This ongoing thermal stress impacts coral health and can shift the balance of their microbial partners, making them less resilient.
Pollution also threatens Mediterranean corals. The Mediterranean is one of the most polluted seas globally, with over 600,000 tonnes of plastic entering it annually. Microplastics can impair coral growth and reproduction, while chemical runoff and industrial pollutants, such as carbon particles from fossil fuel combustion, can embed in coral skeletons. Eutrophication, caused by excess nutrients from pollution, can promote the growth of invasive algae that smother corals.
Destructive fishing practices, such as bottom trawling and the use of ghost nets, directly damage coral colonies and their habitats. Overexploitation, particularly of red coral harvested for jewelry, has reduced population sizes and hindered recovery. Additionally, direct human impacts from tourism, including anchoring and unregulated diving, can cause physical damage to fragile coral structures.
Conservation Efforts
Strategies are being implemented to protect Mediterranean corals and mitigate threats. The establishment of Marine Protected Areas (MPAs) is a primary conservation tool, limiting destructive human activities like fishing and anchoring in designated zones. MPAs have demonstrated effectiveness in allowing coral colonies, such as red coral, to partially recover to levels seen decades ago.
Research and monitoring programs help understand coral health and environmental impacts. Projects like DEEP CORE (Deep Coral Restoration Effort) aim to identify threatened deep coral areas and develop adapted restoration techniques. Ecological restoration projects, including coral gardening, involve growing coral fragments in nurseries and then transplanting them back to degraded areas of the seabed.
Organizations like Coral Guardian and Coral Soul are involved in these efforts, focusing on cleaning seabeds, restoring ecosystems, and raising awareness. International agreements and national legislation regulate activities that impact corals, such as the trade of precious corals. Public awareness campaigns and responsible tourism initiatives encourage divers and visitors to support conservation efforts and minimize their impact on these delicate ecosystems.