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Tropical Rabbitfish Threaten Mediterranean Ecosystem

Sep 18, 2014 04:43 PM EDT

Tropical rabbitfish are devastating algal forests in the Mediterranean Sea, and as the climate continues to warm, they can potentially threaten the region's entire ecosystem, according to new research.

As described in the Journal of Ecology, scientists from the University of New South Wales (UNSW) surveyed more than 1,000 kilometers (~620 miles) of coastline in Turkey and Greece, where two species of rabbitfish have become dominant since they moved into the region via the Suez Canal.

"The study identified two clearly distinct areas - warmer regions with abundant rabbitfish and colder regions where they were rare or absent," Dr. Adriana Vergés of UNSW Australia said in a press release.

Researchers found that in those areas teeming with rabbitfish, they were more like rocky barrens than the typically lush algal forests. Large seaweeds were reduced by 65 percent, numbers of other algae and invertebrates dwindled 60 percent, and overall, there were 40 percent less species in the studied areas.

The two tropical rabbitfish species in question were first reported in the eastern Mediterranean in 1927 and 1956 and have just recently been found living as far west as Croatia and the south of France.

As the world warms in the face of global warming and climate change, it's driving these algae-eating fish to foreign waters, devastating local populations.

"Increased feeding by plant-eating tropical fish in temperate waters as a result of ocean warming is an issue of global importance that has the potential to transform marine ecosystems, as has also been seen in Japan," Vergés noted.

Algal forests, or seaweeds, are essential to marine ecosystems because they provide food and shelter to hundreds of species, and fulfill a role similar to trees in terrestrial forests.

After conducting a series of experiments in regions known to have these rabbitfish, the researchers were surprised to find that it was not necessarily a case of the tropical fish eating more algae than the native fish.

"The native temperate fish actually ate adult algae at a greater rate than the tropical rabbitfish. However the two rabbitfish consumed both young and adult algae, whereas native fish only ate adult algae. So the two rabbitfish can completely denude large areas by working together and having one species that targets adult algae and another species that removes the youngest algal recruits, preventing them from making a forest," Vergés explained.

"This research highlights the need to work out how the interactions between different species will change in a warming ocean," he added.

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