In 2017, a marine heat wave bleached this coral reef in Hawaii’s Hanauma Bay. Now, officials are bracing for a new bleaching event driven by unusually warm ocean waters.
Ozgur Coskun/Alamy Stock Photo
By Warren Cornwall
In the fall of 2014, marine ecologist Jennifer Fisher was stunned when jellyfish and tiny crustaceans typically found in warmer waters filled her nets off the coast of Oregon. The odd catch was just one sign of the arrival of a vast patch of warm water that came to be known as “The Blob”—a massive marine heat wave that lasted 3 years and dramatically disrupted ecosystems and fisheries along North America’s Pacific coast.
Now, with oceanographers warning that a new Blob could be forming in the Pacific Ocean, Fisher is again preparing for strange encounters when she heads out on a research cruise later this month. “This is a very similar situation,” says Fisher, who works at Oregon State University’s Hatfield Marine Science Center in Newport.
This time, however, Fisher and other scientists say they won’t be taken by surprise. They are preparing to more quickly share data on heat wave impacts with each other and with managers who may have to impose new catch limits to protect valuable fisheries. When The Blob arrived 5 years ago, “we didn’t realize the impact” it would have, recalls Toby Garfield, a physical oceanographer with the National Oceanic and Atmospheric Administration’s (NOAA’s) Southwest Fisheries Science Center in San Diego, California. “We’re going to stay ahead of this one.”
NOAA scientists first noticed the growth of an eerily familiar patch of warm water in the north Pacific in August. It now covers an area the size of Australia, stretching from the Hawaiian islands to the Gulf of Alaska. Farther north, the Bering Sea between Alaska and Russia is also experiencing a record-setting marine heat wave, triggered by a sweltering summer in 2018 and a lack of winter sea ice.
There are already some signs of potential impacts. Unusual toxic algae blooms recently hit beaches stretching from California to Washington. In Hawaii, some coral reefs are starting to bleach, turning pale as the corals expel their colorful symbiotic algae in response to heat stress. NOAA is forecasting widespread coral bleaching and deaths in Hawaii over the next 12 weeks.
In the Bering and Chukchi seas to the north, NOAA announced on 13 September that it is investigating the deaths of nearly 300 seals—five times the average—since June 2018. The agency pointed to warmer water as a potential factor in the unusual die-off.
Much like the original Blob, the new warm patch consists of water as much as 3°C above normal. As before, it formed because winds that normally stir up the ocean and draw cooler, deeper water to the surface have been relatively calm, allowing warm waters to persist. But it’s not yet clear whether the patch will evolve into a full-fledged Blob, which was distinguished by its size, duration, and depth. The Blob’s warmth penetrated hundreds of meters below the surface, but the new one extends only about 30 meters deep. If a big storm swept through, the patch “could go away tomorrow,” Garfield says.
Still, scientists are concerned. Garfield says talk of the patch dominated a regular call held last month by a group of Pacific coast scientists and managers he leads. So far, researchers note the warm water has mostly kept its distance from biologically rich coastal areas. But federal scientists are closely watching the heat wave’s evolution with data from satellites, instrument-equipped buoys, and a network of underwater drones that rise and sink through the water column. Scientists on routine monitoring cruises and beach surveys are watching for early warning signs of ecological shifts.
Researchers are also keeping a close eye on lucrative fisheries in the Gulf of Alaska. Surveys this year have found low numbers of juvenile pollock and Pacific cod, linchpins of the fishing industry. Scientists have started to count larvae of key species in nets as soon as they come on board research vessels, rather than waiting for lab results. That way managers have more timely information for setting fishing limits. “We are certainly making an effort to get our data and observations out there as fast as we can,” says Lauren Rogers, a biologist at NOAA’s Alaska Fisheries Science Center in Seattle, Washington.
For some, the troubling news is tempered by the opportunity to test possible solutions. At the University of Hawaii’s Institute of Marine Biology in Kaneohe, researchers have been working to breed corals able to resist higher water temperatures. Now, they are pumping water from the warming ocean into tanks filled with the tiny corals, to see whether they will survive. Coral ecologist Crawford Drury says, “To know that an event like this is coming, and to be able to test what we have been working on for years, is a great chance that not many people get.”
Source: Science Mag