A White House for Anemonefish

A White House for Anemonefish

A shining white anemone provide a wonderful contrast for the clownfish Amphiprion ocellaris

Coral bleaching is a natural phenomenon of zooxanthellae (the symbiotic algae necessary for the survival of many hard and soft corals) expulsion that some corals and anemones realize in presence of high temperature, which induces the production of toxins by their symbiotic “allied”. In this case, the enemy comes from inside and should be eliminated, and the animal eliminates the microalgae. Sadly famous is the massive coral bleaching induced by “El Niño” in the 90s, especially in the Indian Ocean. Other events of coral bleaching have been recorded worldwide, including the Great Barrier Reef and the Indo-Pacific area (Indonesia, Malaysia, Philippines). Some of these areas are giving signs of recovering, but the increasing temperature remains a critical threat for every coral reef. Recently, some diving spots all around Asian reefs presented a quite unusual incidence of sea anemones bleaching, due to the higher sea temperature recorded in this year. Even though they are a great photographic opportunity – the main sea anemones inhabitants, clownfish (even called anemonefish) with their bright colors make a wonderful color contrast with the white background – the shining white sea anemones are not a really good signal for coral reefs health.

A Clarki anemonefish Amphiprion clarkii inside a bleached Heteractis crispa.

Even when there is not a massive coral bleaching same as that occurred in many parts of the world, too many sea anemones bleaching in a given area are a warning signal that we have not to underestimate, even if natural cycles of warmer waters can occur in some areas.

In Indonesia, in the North Sulawesi Area (Bunaken, Manado Coast, Lembeh Strait just to cite the most renewed areas!) first signals of bleaching went from Magnificent Sea Anemone (Heteractis magnifica) that apparently is the most sensitive species in the area. At the moment, other species as Heteractis crispa and the bubble sea anemone Entacmaea quadricolor are giving signs of bleaching.

Anemones’ bleaching is not an instantaneous process: anemones start loosing color slowly, passing from their natural to a greenish-brownish one, before to become something like a fluorescent green and finally completely white.  In some occasions, especially in dive sites that I visit more commonly, it has been possible to monitor the color changes, from the normal one to the completely white phase.

A pink anemonefish Amphiprion perideraion inside a bleached Magnificent Sea Anemone Heteractis magnifica

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