Discovery of soft coral species offers new evidence Mediterranean turning tropical

A soft coral, commonly found in the Indo-Pacific region and off the southern Israeli Red Sea coast, has been identified for the first time in the Eastern Mediterranean, in a possible further indication that the latter is slowly becoming tropical due to climate change.

Corals from the Dendronephthya genus (group of species) were found 42 meters (138 feet) deep off the coast of Kibbutz Sdot Yam, south of Haifa, in northern Israel.

The discovery was made during a routine dive for a long-term research program being carried out by the Morris Kahn Center for Marine Research at Haifa University.

“Until now, the low temperatures in the Mediterranean Sea during winter prevented tropical corals from entering the area,” said research student Hagai Nativ from Haifa University’s Charney School of Marine Sciences.

“The presence of Dendronephthya suggests that at least last winter, the water in the Mediterranean Sea was warmer than in the past.”

He went on, “It is still too early to predict the ramifications of the specific coral species we found, but the finding provides further evidence that the natural barriers between the Mediterranean and the Red Sea are disappearing due to climate changes.”

The coral was discovered in May, and the research results were published in the international peer-reviewed journal Biology.

The only other Red Sea soft coral to be identified to date in the Eastern Mediterranean is Melithaea erythraea. That was first documented in the waters warmed by the Hadera power plant, just off the central coast, in 1999.

Corals from the Dendronephthya genus discovered off the coast of Kibbutz Sdot Yam, south of Haifa, in northern Israel. (Hagai Nativ, Morris Kahn Center for Marine Research, Haifa University)

To survive, corals need water temperatures that range between 17°C and 30°C (62.6°F to 86°F).

In recent years, due to climate change, water temperatures in the Eastern Mediterranean have been climbing by 0.27°C to 0.35°C  (0.49°F to 0.63°F) per decade, the researchers said.

Minimum winter temperatures in coastal waters have increased from around 16°C (60.8°F) to 18°C (64.4°F) since the 1990s.

According to Tal Ozer, who studies the southeastern Mediterranean and coordinates data for the national marine monitoring program at the Israel Oceanographic and Limnological Research Institute, surface water temperatures in March in Hadera, where one of two Mediterranean monitoring stations is located, never dipped below 18.6°C (65.5°F). That was 1.2°C (2°F) higher than the average for the past 12 years.

The researchers emphasized that the Dendronephthya coral did not constitute a threat in itself and that it was too early to predict what changes, if any, would result from its arrival.

“But in a complex system such as the marine ecosystem, even a small change can spark a chain reaction that leads to major change,” they said.

Given this coral’s ability to stick to surfaces and grow by several centimeters a month, they added, “We expect it to rapidly expand its distribution and abundance across the Mediterranean Sea.”

Corals from the Dendronephthya genus found off the coast of Kibbutz Sdot Yam, south of Haifa, in northern Israel. (Hagai Nativ/Morris Kahn Center for Marine Research, Haifa University)

And if the species of crab with which it lives symbiotically in the Red Sea follows it into the Eastern Mediterranean, that too could establish a presence, they went on.

“When species from one place invade and settle in another, it can cause serious problems for the local environment,” they wrote. “These invasions, known as bio-invasions, disrupt natural ecosystems and can lead to major changes. The Mediterranean Sea is especially at risk because the water conditions are changing rapidly due to climate change, which, coupled with the opening of the Suez Canal, creates an appropriate environment for species from the Red Sea to move in.”

“The climate change we have experienced recently, alongside the expansion and deepening of the Suez Canal, are creating favorable conditions in the Mediterranean for the migration and population establishment of species from the Red Sea.”

More than 500 alien species of fish, invertebrates, and algae have moved from the Red Sea into the Eastern Mediterranean Sea via the Suez Canal, going on to establish permanent populations elsewhere in the Mediterranean.