The ridge of sod coral on Mljet is the largest coral reef in the Mediterranean

An almost endemic reef builder, sod coral (Cladocora caespitosa), has inhabited Mediterranean waters for at least three million years. Its largest and most developed populations are located in Croatia, in the Mljet National Park.

The ridge of sod coral in the Great Lake on Mljet covers an area of ​​as much as 650 square meters, and is located at a depth of between 4 and 18 meters and is one of the largest in the world, and is the largest coral reef in the Mediterranean. Unfortunately, rising sea temperatures threaten the survival of the coral reef. Back in 2018, the National Park started removing invasive algae, which is a resident of tropical to moderately warm seas and negatively affects the biodiversity of indigenous species.

In the Mediterranean, this alga was first recorded in the early 20th century, and in Croatia in 2000, and is spreading rapidly as well as its negative impact on marine life. It was first recorded on Mljet in 2004 in the Solin Channel, which is also the junction of the sea and the Great Lake, and in the Gonoturska Bay.

The national park has since been working to remove algae by covering with foil, manually collecting and vacuuming underwater pumps to reduce its impact on the coral reef and other wildlife.

Duje Bulaja YouTube video channel: Mljet coral reef 2015

- In the waters of the Mljet National Park, the coralligenous community has been monitored for years, which is increasingly endangered by rising sea temperatures due to climate change, so we often record coral deaths in the summer months. The sea heats up to ever greater depths and stays so heated for a longer period of time which has negative effects on the sessile (immobile) organisms that live there. Assoc. prof. dr. sc. Petar Kružić and his team are monitoring the condition of macrobenthos species and populations and their endangerment at certain stations this year as well, and special attention is paid to the protected species of red coral, which is additionally endangered by uncontrolled extraction., announced the Mljet National Park yesterday on its social networks.

Sod coral is a slow-growing, long-lived species with extremely slow dynamics and reduced ability to recover. Low rates of self-renewal will hardly be able to balance with the increased mortality rate caused by sea warming and other impacts, warn the International Union for Conservation of Nature (IUCN).

Mass mortality of these corals was observed as early as the summer of 1999, and the extremely hot summer of 2003 caused a high mortality rate of sod coral over a wide area, including exceptional populations on Mljet and the Columbret Islands. In some parts of the Columbret Islands, 50 to 80 percent of these corals have become extinct, experts say.

YouTube channel Mljet National Park Video author Vedran Kunica

Last year, Vedran Kunica shot a video of coral that NP Mljet shared on its social networks

- This is one of the attractions of the Mljet National Park and actually the Great Lake in the National Park. Unfortunately, there are not many videos of this locality and little is known, but it is a habitat of sod coral which is endemic to the Mediterranean., the author of the video told Slobodna Dalmacija last year Vedran Kunica adding that these corals are smaller in size and are present in smaller numbers, for example in the Bay of Mali Ston, but exclusively at that microlocation in the Great Lakes. Due to the strong current, extremely large coral reefs are formed, which with their configuration and appearance actually resemble large coral reefs of warmer seas, warm tropical seas. 

- Also, the abundance of fish is amazing! Since fishing is forbidden there, the fish has become domesticated, it is calm, it allows a closer approach, which is obvious from the video I shot, he said Vedran Kunica za Free Dalmatia who donated the video to the Mljet National Park, which shared it with the public.

- See the extraordinary richness of life on and around the coral reef in the video by Vedrana Kunica. The main task of Mljet National Park is to preserve natural values ​​so that future generations can enjoy such scenes, reads the post description of this fascinating video of the Mljet submarine.


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