October 10, 2017
Coral bleaching is a well-known consequence of climate change. What is less widely known is that sea anemones suffer the same fate, and this reduces the fertility of clownfish living in these anemones, as researchers from the CRIOBE, a laboratory jointly managed by the CNRS, the EPHE and Université de Perpignan Via Domitia, have just demonstrated in French Polynesia. Following a 14-month study, they are publishing their results in Nature Communications on Oct. 10, 2017.
Like corals, sea anemones live in symbiosis with microscopic algae, which gives them their color. Symbiotic clownfish protect themselves from predators by sheltering among the anemones' tentacles, and each month, lay eggs at their base. The anemones are also protected by the clownfish that they host.
Every other day, from October 2015 to December 2016, researchers and students visited 13 pairs of clownfish and their host anemones in the coral reefs of Moorea Island (French Polynesia). This monitoring was conducted before, during and after the 2016 El Niño event that triggered a warming of the Pacific Ocean (+2°C on Moorea Island compared to the 2007-2015 average—a combined effect of ongoing global warming and the El Niño episode) and a worldwide coral bleaching episode. Half of the anemones monitored in this study bleached as they lost their microalgae. Among the clownfish living in the bleached anemones, the scientists observed a drastic reduction in the number of viable eggs (-73 percent). These fish were laying eggs less frequently and they were also laying fewer and less viable eggs, while these parameters remained unchanged among fish hosted by unbleached anemones.
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