Fish Species Losing Homes As Sea Anemones Suffer From Bleaching

Brett Smith for – Your Universe Online

Marine biologists have been warning recently about the dangers of coral bleaching and new research from a team of international scientists indicates sea anemones are also susceptible to the color-sapping phenomenon that is thought to result from death of sea creatures’ symbiotic algae.

In addition to being suspected of causing an increase in sea anemone mortality, bleaching also affects clownfish and 27 other fish species that depend on anemones for shelter from predators, according to the team’s report published in the journal PLoS ONE. Experts suspect bleaching occurs when the surrounding water gets too warm for symbiotic algae.

“Our study showed that at least seven of the ten anemone species suffer from bleaching when water temperatures get too high,” said study researcher Ashley Frisch of the ARC Centre of Excellence for Coral Reef Studies at James Cook University. “Importantly, we found bleaching of anemones occurring wherever we looked – from the Red Sea and Indian Ocean to the Indo-Australian region and the Pacific. Sometimes it was on a massive scale.”

In the study, the marine biologists said bleaching most likely causes increased mortality, based on their observations of the sea floor.

“Anemones are naturally tough and live for many years,” Frisch said. “As a result their rates of reproduction are slow – and when they are hit by a killer bleaching event, it can result in their complete loss from an area over a period of time.”

The Australian scientist said the loss of anemones also has a knock-on effect for those fish that depend on them for shelter, like the clownfish from the popular Disney movie ‘Finding Nemo.’

“Bleaching causes the loss of anemonefish, like Nemos, which have nowhere to hide and without the anemones to protect them are quickly gobbled up by predators,” he said. “Also, because the fish appear to perform useful services for the anemone like protecting them from grazing fish, it may also be that the loss of anemonefishes following a bleaching event means the anemones themselves are much less likely to recover.”

In the study, scientists from the United States, Saudi Arabia and Australia observed almost 14,000 anemones around the globe. While they found only 4 percent of the Earth’s anemones are bleached, bleaching rates ranged from 20 to 100 percent following five major bleaching events.

The team concluded the anemone “population viability will be severely compromised if anemones and their symbionts cannot (acclimate) or adapt to rising sea temperatures” in some areas.

“Anemone bleaching also has negative effects to other species,” the researchers noted, “including reductions in abundance and reproductive output of anemonefishes.

“Therefore, the future of these iconic and commercially valuable coral reef fishes is inextricably linked to the ability of host anemones to cope with rising sea temperatures associated with climate change,” the report said.

“If host anemones (and their symbiotic algae) cannot acclimate or adapt to rising sea temperatures, then populations of host anemones and associated anemonefishes are anticipated to decline significantly,” the report concluded.

Frisch said anemones and the fish they protect also have value with respect to tourism and the aquarium trade. Numerous poor coastal communities rely on the income they impart, he said.