Project Manaia

What you should know about Mediterranean Coral

The Mediterranean Sea has witnessed centuries of change to the life forms that reside within its bright blue waters. Before it was the Mediterranean Sea, it was the ancient Tethys sea with its own special blend of flora and fauna. In the subsequent years- 200 million give or take, this body of water separating Europe from Africa has dried out and replenished itself countless times, and the coral types there have undergone their own metamorphosis.

underwater photo

All about coral

 There are coral forms found specifically in the Mediterranean. But this miniature ocean known as a hotspot for biodiversity is also a hotspot for anthropogenic activities – coastal urbanization, shipping, fishing and tourist activities may mean the end of corals in the Mediterranean. To explore the coral in the Mediterranean is to learn about the richness and complexities of the region.

Photo by Francesco Ungaro

Orange coral

Astroides calycularis

As the name suggests, this coral (Astroides calycularis) is a vivid orange but it can also be a bright ,sun-yellow with tentacles that stick out and sway with the ocean currents. It is a stony cup coral found specifically in the Mediterranean Sea. It can sprout on rocky areas located on the surface and also in caves.

This species tends to group together acting as a single organism – a series of interconnected polyps weaving together a carpet of orange on the ocean bottom. A possible explanation for this behavior is that they have limited ability to disperse their polyps across the ocean so they choose to stick close to each other.

In terms of feeding, orange coral has several mouths which feed on organisms as large as jellyfish and microscopic, floating animals called zooplankton.

Reports of orange coral mostly occur in the south-western section of the Mediterranean basin from the Strait of Gibraltar to Sicily, Spain, Algeria, Tunisia and Morocco.

 Orange coral can thrive at fairly high temperatures and is considered a warm water species. This means it is suited to warmer conditions. But temperature fluctuations negatively impact its health

Zigzag coral

Av NURC/UNCW and NOAA/FGBNMS - NOAA Photo Library, Public Domain,
Mediterranean Coral, Zigzag Coral. Av NURC/UNCW and NOAA/FGBNMS – NOAA Photo Library, Public Domain.

 Zig zag coral, or  madrepora oculata, is a hard coral with a fragile skeletal frame that reaches out like the branches of a tree. It is mostly found in the northwest of the Mediterranean Sea.It takes up space in the canyons there- the Cap de Creus and Lacaze-Duthiers canyons. It enjoys feeding on zooplankton like orange coral does. A thriving and well-fed zig zag coral can reach heights as high as 50cm.

 It is known as a cold-water coral because it can grow in dark, deep waters  like those found in the Cap de creus Canyon .It has been found at depths as low as 540m. Its actual range spans from 55-1950 meters (that’s pretty deep!). This coral type is found in regions of France, Italy, Spain and Greece where these countries have rights to take advantage of marine resources.

Red gorgonians

Image by José A. Moya from Pixabay
Mediterranean Coral, Red Gorgonians. Image by José A. Moya from Pixabay

The color of scarlet, these stony corals are famous in the Mediterranean. They are widespread stretching all across the dimly lit Mediterranean coasts. Red gorgonians are a part of the gorgonian forests found at the bottom of the Mediterranean Sea.

Algae likes to grow on the hard surface of this coral which attracts a wide set of marine life. They even provide shelter for the sea creatures that feed there. The gorgonians’ ability to form habitats makes this coral shine in the context of the Mediterranean. It is one of the key hotspots for biodiversity; Flora and fauna love it in this cherry-red, underwater forest.

 Red gorgonians take a long time to grow but can live for many years-100 years actually, and they live in 20 to 130 meters deep water. Scuba divers regularly swim these distances to gaze upon the ruby red beauty of the gorgonians.

Divers and slow growth rates harm the gorgonians. That is why they are considered a vulnerable species.

So, what’s killing the coral?

A major threat is people. Coral in the Mediterranean (and everywhere else) face a myriad of threats from human beings. Anthropogenic activities- fishing, scuba diving, anchoring and tourism- are major culprits in the mass mortality events of coral in the Mediterranean. Let’s take a look.


Fishing wreaks havoc on the corals at the bottom of the ocean floor. It’s scary to think about how a net or a trawl can change the future of a coral species but that’s the reality. Nets entangle while trawls scrape the coral changing their behavior and shape. 

Ghost fishing- Fishing gear gets lost or discarded often in the Mediterranean. Ghost gear can fish all on its own. Haunting the bottom of the ocean floor, the gear gets entangled in coral beds smothering habitats. Coral species on the ocean floor, specifically gorgonians get trapped in the abandoned nets, pots and traps.

Over 50 to 60 years, half of the zig zag coral population has died out. This delicate coral can not bear the weight of bottom trawls dragging across them. Not even in  canyons are zigzag coral safe from harmful fishing  practices.

Thanks to poor fishing practices, the newly exposed skeletons of the coral are now at risk for parasitic attack. Remember the jellyfish eating orange corals?

 Negligent fishing practices are a double-edged sword for them. The physical destruction of the coral decreases their abundance; this reduces the polyps’ ability to work together to feed. No feeding means low nutrition for the coral. 

Also, recreational and illegal harvesting are carried out in the Mediterranean.These activities have been reported in areas where orange coral is found. It gets worse. Local fishermen sometimes use poisons to catch octopuses near coral reefs. All of these activities inch the corals closer to death.


Recreational scuba-diving is up next. Orange coral and red gorgonians have experienced major declines because of it. Medes island in Spain has high diving activity.

Photo by Juanma Clemente-Alloza on Unsplash
Mediterranean Coral with diver. Photo by Juanma Clemente-Alloza on Unsplash

 Around 60,000 dives happen each year. In shallow gorgonian gardens, diving activity killed the coral by three times the normal rate.

Coastal development for tourism is ever expanding, so land-use near the coast is inevitable. As a result, the  plight of coral species increases with the construction each new hotels and golf courses t. This land use adds storm-water runoff  and sewage to the sea.

Another overlooked impact of coastal development is this:  artificial light production. Artificial light associated can negatively impact zooplankton which ,by now you know, coral love to feed on. If zooplankton go, coral will follow. Other harmful activities based in tourism are: Anchoring boats and sunscreen wearing.


Photo by Jeff Stapleton:
Oil rig. Photo by Jeff Stapleton

 Off-shore Oil mining can involve the following: drilling the sea floor and laying submarine cables and pipelines. Extraction events naturally create sediment. Sediment and mining go hand in hand. The sediment settles on the ocean floor then blankets the coral in large swaths clogging coral tissues. Offshore oil mining and gas exploration contracts have been ramping up in the Mediterranean. Energy demands need to be met and the ocean must bear the cost.

The vastness and beauty of the coral in this miniature ocean has sparked wonder and curiosity for centuries. But, if we aren’t careful, the destructive nature of human activities may mean the death of coral in the Mediterranean.

Written by Ayanna Adams

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