A large mass of unusually warm water in the Pacific Ocean off the western coast of the U.S. has marine biologists and weather scientists once again concerned — a "blob" just like this lingered for a year and a half in the ocean between 2014 and 2016, leading to a toxic algae bloom and lots more problems.

A warming trend has been at work in the Pacific since June, and now off-shore ocean temperatures are showing as much as seven degrees above seasonal averages. Biologists with the National Oceanic and Atmospheric Administration (NOAA) tell the Chronicle this week that they're concerned that once again the "blob," which looks even warmer than the one that took shape in September 2014, will cause havoc for marine life up and down the coast.

"I am surprised to see something like this develop again so soon after what looked like the end of the marine heat wave in 2016," says Nate Mantua of the NOAA’s Southwest Fisheries Science Center in Santa Cruz, speaking to the Chronicle. "If this persists and it spreads to the coast, then I think it would be bad news for marine life and many fisheries along the West Coast."

As NOAA Fisheries reports on their site, the current blob has "quickly grown in much the same way, in the same area, to almost the same size." And while this "blanket" of warm water, about 100 to 150 feet deep across the ocean surface, hasn't yet reached the coast, it will be extremely disruptive and deadly if it does.

"It’s on a trajectory to be as strong as the prior event,” says Andrew Leising, a research scientist at NOAA Fisheries’ Southwest Fisheries Science Center in La Jolla, California. "Already, on its own, it is one of the most significant events that we’ve seen."

As many will recall, one of the most significant impacts of the last "blob" was that the warm water gave rise to a huge bloom of toxic algae — one of the biggest that scientists had ever observed — which in turn poisoned the Dungeness crab supply along the Pacific, leading to the entire crab fishing season being canceled. (The crabs showed high levels of domoic acid, from the algae, which can cause seizures and worse if consumed by humans.)

Other impacts included mass starvation of sea lions, failed salmon runs, and whales coming in closer to shore to feed and getting tangled in crab fishing gear, as the Chronicle notes. It can also affect the weather, potentially leading to another prolonged drought, if it sticks around.

The current "blob" is officially being called the Northeast Pacific Marine Heatwave of 2019, and it was caused by "a ridge of high pressure [that] dampened the winds that otherwise mix and cool the ocean’s surface," per the NOAA. And it's still too early to get too concerned, scientists say, because it could dissipate as fast as it formed. With a depth of only about 150 feet, it's nowhere near the depth of the earlier blob, which reached as deep as 1,000 feet four years ago.

And as the Washington Post reports today, such dangerous "hot zones" have been cropping up all over the planet, pointing as well to a large "blob" of warm water in the Atlantic Ocean that first appeared in the mid-1990s and has lingered and grown larger ever since.

"There are definitely concerning implications for the ecosystem," says Nick Bond, a research meteorologist with the Joint Institute for the study of the Atmosphere and Ocean in Seattle, who coined the term "The Blob" for the previous 2014 event. "It’s all a matter of how long it lasts and how deep it goes."