Reef Ramblings

In my article, “2010, the International Year of Biodiversity - Clownfishes.” under the section entitled, “Can clownfish adapt to climate change?” there was a mention that one species of clownfish had recently been shown to use soft corals as an alternative habitat, something previously only seen in captivity. This is referenced to Arvedlund, M., and Takemura, A. (2005) Long-term observation in situ of the anemonefish Amphiprion clarkii (Bennett) in association with a soft coral. Coral Reefs 24, 698-698.

Having managed to track this paper down I can now expand on the reference.

Between May 2003 to December 2004, during the course of 37 daytime snorkeling surveys between the hours of 11.00 and 18.00, an adult Amphiprion clarkii was observed at a depth of 1 m, living in the same soft coral, a Lobophytum species of around 90 cms in diameter.

This took place in the Ryukyus Archipelago in southern Japan, at the southernmost local reef of Sesoko Island. This area was seriously affected by the global bleaching event of 1998; in the aftermath of this event several species of host anemones disappeared while the surviving anemone species declined. At the time of the paper, 2005, the anemone population had yet to recover.

Although anemonefishes are known to adopt a wide range of soft corals in captivity, this form of behaviour is almost unknown in the wild.

All 28 known species of anemonefishes have an obligate symbiotic relationship with at least one of ten species of anemones belonging to the families: Actiniidae, Stichodactylidae and Thalassianthidae. There tend to be species specific associations which range from Premnas biaculeatus, Maroon Clownfish, associating with a single species of anemone, Entacmea quadricolor, Bubble-tipped Anemone, to Amphiprion clarkii which has been found in association with all ten species of known host anemone.

From personal observation, the main author of the paper, reports that A. clarkii will often take shelter away from its host anemone when pursued by a potential predator whereas most other anemonefishes, take refuge in their host anemone.  The paper ends by speculating whether the ability of A. clarkii to associate with a wide range of anemones and, as has now been observed, with corals might go some way towards explaining why it’s the most widely distributed species of clownfish.

Other than the fact that Lobophytum species soft corals are amongst the most toxic of corals, something that might deter predation by fishes and aid the coral in competition against other corals, this species appears to offer little in the way of protection for a clownfish. This leads me to further speculate whether A. clarkii is evolving away from its obligate association with host anemones or to question if this is just one fish that has been unfortunate enough to lose its host yet been lucky enough to survive for so long in the absence of an anemone.

More reports of clownfishes, particularly A. clarkii, are required before we can come to any conclusions.

Tim Hayes

Midland Reefs

©2010

Although we tend to associate coral bleaching with elevated water temperatures, it may not be as widely known that it can also occur when water temperatures drop below the low limit of coral survivability, 15 ˚Celsius. Bleaching occurs when a coral undergoes stress and loses or expels its zooxanthellae, or symbiotic algae, with prolonged stress resulting in coral death.

Cold-water Bleaching on the Reef.

The recent sustained low water temperatures in South Florida and the Florida Keys have triggered severe coral bleaching and coral fatalities. Temperatures in some areas of the Florida Keys National Marine Sanctuary have dropped to as low as 11 ˚Celsius for several days, well below average for the time of year. This is the first time that cold-water bleaching and die-off has occurred in Florida since the late 1970s.

“The Keys have not seen a cold-water bleaching event like this since the winter of 1977-78, when acres of staghorn coral perished,” said Dr. Billy Causey, southeast regional director of NOAA’s Office of National Marine Sanctuaries. “But today we are better prepared to document and assess the impacts of stress thanks to numerous partners.”

Over the next two weeks, teams of science divers from federal and state agencies, non-governmental and academic organizations, will be surveying the reefs to assess and monitor mortality and changes in coral health.

“If there is any ‘good news’ it’s that reef managers and scientists are able to quickly respond to this event and are in a good position to learn more about how reefs will rebound following such a rare occurrence,” said Chris Bergh, director of The Nature Conservancy’s Coastal and Marine Resilience Program.

Usually the Florida Reef Resilience team carries out surveys following warm-water bleaching events. Activating the team now will provide valuable insights on what happens to corals when they get too cold. Monitoring needs to be implemented as quickly as possible, because macro-algae and cyanobacteria quickly invade or overgrow dead coral making identification of recently deceased corals difficult.

Reports so far indicate that all species have been equally affected by the cold, though more will be known when the results of the survey are in. It seems that offshore reefs have fared better than inshore and mid-channel reefs.

The coral reefs of the Florida Keys are part of a unique and diverse ecosystem that forms the third largest barrier reef in the world. Reef-related expenditures generate more than $4.4 billion annually in southeast Florida and reef recreation supports more than 70,000 jobs.

Cold-water Bleaching in the Aquarium.

Cold-water bleaching can also occur in the reef aquarium. During the very cold weather of December 2009 - January 2010, I experienced this phenomenon in one of the Midland Reefs research tanks. Interestingly it was a half a dozen or so Entacmaea quadricolor, Bubble-tipped anemones, that were affected rather than any of the stony corals in the system.

The problem was caused, as you might have guessed, by a couple of defective heaters. These had been running since the system had been set-up so were in the region of 8 years old, As an aside, I’ve noticed numerous equipment failures in the fish house over the last year so I’m now minded to change many items of equipment, heaters, ballasts, pumps, etc. once they reach the 6 year mark. After all, no item of equipment is going to last forever, especially non-serviceable items such as ballasts, ignitors, and heaters.

So far the anemones are remaining in good health, they’re feeding well and producing nematocysts but there’s not yet any sign of recruitment of new strains of zooxanthellae.

I feel an experiment coming on to ascertain whether the anemones can use the strains of zooxanthellae present in the corals that they share the system with. I’ll try removing half of the bleached anemones to a system containing unbleached specimens of the same species and then compare the two systems for signs of zooxanthellae recruitment.

And in the meantime, whilst I’m awaiting results of the experiment, it’s time to search the science for more information regarding zooxanthellae and which organisms that they choose to inhabit.

Tim Hayes

Midland Reefs

©2010