By Hemmy So, LA Times Staff Writer
August 3, 2006

Hundreds of dead or dying purple sea urchins washed up into the Little Corona Marine Life Refuge tide pools in recent days, a phenomenon some officials blame on warmer-than-usual waters.

"On Monday there were two or three hundred that littered just the tide pool area," said Amy Stine, Newport Beach marine life refuge supervisor. Normally, she said, she sees at most three urchin shells a day.

"Most of them that are now left on the shore are dead. The sea gulls are having a heyday with them," Stine said.

Ocean temperatures climbed above 75 degrees during the last couple of weeks, warming normally chilly waters along the Southern California coast. Last weekend, Huntington Beach recorded a water temperature of 81 degrees.

While surfers rejoiced by shedding wetsuits and fishermen reeled in tropical fish, warm waters might have hurt sea creatures that thrive in a colder environment.

"Water temperature is everything to marine animals," said Dennis Kelly, professor of marine science at Orange Coast College in Costa Mesa. "Their world tends to be a lot colder than ours, especially around here."

Warmer water also holds less oxygen, potentially causing marine life to suffocate, said Bob Burhans, curator of fish at the Birch Aquarium at Scripps Institution of Oceanography in La Jolla.

The tide pool landscape may also be a factor in the deaths, said Pat Leahy, director of the Kerckhoff Marine Laboratory in Newport Harbor, part of Caltech. For those purple sea urchins living in the area uncovered at low tide, the lack of constant cool tide water and the hot surface temperatures might have helped kill them.

"When we had those temperatures a couple of weeks ago, almost 100 degrees, you had those animals in the tide pools and they were frying like eggs," Leahy said, but it takes a while for them to die. "We're seeing effects of it now," he said.

By Wednesday, much of the dead sea urchins had either drifted back into the ocean or been picked up by gulls or beachgoers.

But several sea urchin shells, called tests, were still scattered among the feather-boa and palm kelp, hermit crabs, sea anemones and mussel shells that fill the tide pools.

Kelly warned that because no scientists had examined the sea urchins to determine the cause of death, no one can be certain that higher water temperatures led to the weekend's massive die-off. He noted that other causes of death could include naturally occurring pathogens, pollutants or overpopulation.

"Unless you know the whole story, you're basically just guessing by saying it's the warm water if you don't have any evidence the warm water killed them," he said.

For many experts, however, increased ocean temperatures appear to be the most likely culprit.

Almost every summer sees some sort of marine life die-off due to hot weather and higher water temperatures, said Steve Martarano, spokesman for the state Department of Fish and Game.