Warming water can create a tropical ecosystem, but a fragile one
Warm water discharged into the Sea of Japan let tropical fish flourish in an artificial hot spot
By Jake Buehler
A decade ago, the waters off the Otomi Peninsula in the Sea of Japan, were a tepid haven. Schools of sapphire damselfish flitted above herds of long-spined urchins. The site was a hot spot of tropical biodiversity far from the equator, thanks to warm water exhaust from a nearby nuclear power plant. But when the plant ceased operations in 2012, those tropical species vanished.
After the plant shut down, Otomi’s average bottom temperature fell by 3 degrees Celsius, and the site lost most of its tropical fishes, fisheries scientist Reiji Masuda of Kyoto University reports May 6 in PLOS ONE. The die-off of tropical fishes and invertebrates was “striking,” he says. Otomi quickly reverted to a cool-water ecosystem.
The life and death of the reef is providing a sneak peek into the future of temperate habitats under climate change. This research suggests that even modest warming can result in dramatic changes to cool-water reefs, with some temperate habitats converting to more tropical ones. But these emerging reefs may not match the diversity or health of other more established tropical reefs at first, leaving them as ecologically fragile as the Otomi reef proved to be.
While some temperate reefs are changing rapidly with global warming, they aren’t exact transplants of more established tropical ecosystems, says David Booth, a marine ecologist at the University of Technology Sydney not involved in the new study. Booth studies increasingly tropical Australian reefs.