Coral moves north in response to warming seas

Marissa Cevallos in Science News: Some Pacific corals have done the equivalent of moving from sunny Atlanta to Detroit, possibly in response to rising ocean temperatures. A new study of reefs around Japan reveals that a handful of coral species have migrated from the balmy subtropics to temperate climate zones over the last 80 years. The study is the first to track coral reefs for such a long time and over several latitude lines, a Japanese team reports in an upcoming Geophysical Research Letters.

The team, led by geographer Hiroya Yamano of the National Institute for Environmental Studies in Tsukuba, Japan, analyzed maps of corals from four time periods starting in the 1930s. They found that of nine common coral species, four had expanded northward, and two went as far as temperate waters. The study confirms what marine biologists and fishermen have speculated for years. “There were eyewitness accounts of the occurrence, but the data wasn’t so reliable,” says Yamano. “Now we can show very solid evidence.”

Now it appears that some coral species will migrate — and fast — in response to warming waters. Some species Yamano examined migrated as fast as 8.7 miles per year. Yamano calculated that a sample of land-traveling animals migrate only 0.4 miles per year on average. In 80 years, the fastest corals would travel nearly 700 miles. It would be like land plants making the Atlanta-to-Detroit trek between the Great Depression and today.

Coral reefs are important biologically because they house a diverse group of animals — about one in four marine species call a coral reef home. Reefs are made of animals called polyps with a hard skeleton made of calcium carbonate. Each year, the corals around Japan hatch larvae, which can get swept up by warm Pacific currents from the south called Kuroshio and Tsushima currents. But most larvae normally don’t settle far from home….

Coral detail at Perhentian Island (Malaysia), Platygyra sp. or Oulophyllia sp., shot by pakmat, Wikimedia Commons via Flickr, under the Creative Commons Attribution-Share Alike 2.0 Generic license