6/29/13
Millions of krill — a tiny shrimplike animal at the center of the ocean food web — have been washing up on beaches from Clam Beach, Redwood National Park and Crescent Beach to Southern Oregon for the past few weeks.
Scientists are not sure why.
“We’re still looking into it. We got reports locally a couple days after the mass strandings,” said Joe Tyburczy, Humboldt County coastal specialist with California Sea Grant Extension in Eureka. Most local sightings of the event happened between June 16 and June 18, and were reported mostly by beach goers, he said.
National Oceanic and Atmospheric Administration oceanographer Bill Peterson says the krill may have been blown into the surf by strong winds while mating near the surface, and then been dashed on the beach.
The species is Thysanoessa spinifera. They are about an inch long, and live in shallower water along the Continental Shelf. They have been seen in swaths 5 feet wide, stretching for miles on beaches from Eureka to Newport, Ore. Some were still alive.
“It’s pretty significant. We’re working with other agencies to gather information on this event,” Tyburczy said. Cal Sea Grant is trying to get observations from people who have observed the mass strandings. “Luckily, some people had the presence to collect samples and send them to NOAA,” he added.
“There has definitely been something going on,” Peterson said from Newport. “People have sent us specimens. In both cases, the females had just been fertilized. That suggests they were involved, maybe, in a mating swarm. But we’ve had a lot of onshore wind the last two weeks. If they were on the surface for some reason, and the wind blows them toward the beach, and they are trapped in the surf, that is the end of them.” Or they may have fallen victim to low levels of oxygen in the water, said Tyburczy. A recent ocean survey showed lower than normal oxygen levels in some locations. If the krill went to the surface to get oxygen, they could have been blown onshore, he said.
For some reason, people did not see gulls and other sea birds eating them, he added.
Peterson said low oxygen conditions, known as hypoxia, are a less likely explanation because they normally occur later in the summer.
Tyburczy added that washed up krill were seen June 21 as far south as Bodega Bay.
The mass strandings are unusual, but not unheard of, Peterson added. There is no way to tell yet whether this represents a significant threat to a source of food for salmon, rockfish, ling cod and even whales.
