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Volunteers Rush to Clear 13,500 Pounds of Dead Fish in Marina Del Rey After Record Heat

A stretch of above-normal warmth over the weekend in Southern California created an unwelcome odor as thousands of dead fish covered the surface of marina waters.

While residents and tourists in Marina Del Rey, the largest man-made marina in the U.S., may have enjoyed higher temperatures, the impact on sea wildlife created an unpleasant problem.

Last week brought record-breaking temperatures for the area, including a high of 102 degrees Fahrenheit in downtown Los Angeles on Thursday, May 15.

After investigation, The California Department of Fish and Wildlife (CDFW) concluded the fish likely died of oxygen depletion.

When temperatures rise, oxygen levels decrease in the water due to the decay of algal blooms. Without enough oxygen, fish and other sea organisms cannot survive.

According to the Centers for Disease Control, algal blooms can also block necessary sunlight to the fish along with depleting oxygen.

In a news release, the CDFW said that approximately 300 bags of fish, each weighing 45 pounds, were recovered by Los Angeles County Beaches and Harbors. Most of the affected fish were anchovies.

Cleanup began immediately following the initial signs of a fish kill on Saturday evening. Volunteers from Los Angeles Water Keeper worked swiftly to remove the fish, especially with Memorial Day weekend approaching.

"We're going to move as quickly as possible," said Carol Baker of the Los Angeles County Department of Beaches and Harbors.

Work from the volunteers has already made an impact in bringing the marina back to original shape.

"You hardly see any fish in the water," Baker said. "Visually, the picture is completely different. It's clear."

Along with temperature changes, there are many potential causes to the fish kill.

David Caron, a professor of Biological Sciences at University of Southern California, said that connecting the dots between heat and the algae might not be the only answer, though it is a possible contributing factor.

"The bacterial activity will increase in direct proportion to the temperature," he said.

Caron studied a 2011 fish kill in King Harbor Marina, also near Los Angeles, and sees similarities between the two events.

"My guess is that a number of fish got in there, the oxygen went low enough that some of them started to die. Once they start to die, then things progress very rapidly," he said.

Schools of fish can congregate in small areas for a number of reasons including retreating from predator fish. When too many fish clog one area, the oxygen levels can be depleted due to the volume of fish. Add in higher temperatures, and those levels will decrease at a quicker rate.

Fortunately for the workers, temperatures declined over the weekend, which Caron said will significantly help clean-up efforts.

Alina Corcoran, a research scientist at the Florida Fish and Wildlife Conservation Committee, said that summer temperatures increase the likelihood of fish kills due to the warming of coastal water.

The CDFW said the Marina Del Rey fish kill is not considered to be unusual.

The fish only filled one of the eight basins in Marina Del Rey.