Workers remove hudreds of dead fish from the Malibu Lagoon in California, 27 August 2018. Officials said oxygen levels in the water tested normal, but the temperature in the lagoon was “significantly elevated” — about 82 degrees. Relentless summer heat and a lack of fog along the coast could have caused the temperature of the water to soar. Photo: Los Angeles Times

By Hannah Fry and Alejandra Reyes-Velarde
27 August 2018

(Los Angeles Times) – Authorities made the grim discovery last week: More than 1,000 dead fish floating at Malibu Lagoon.

California State Parks scientists are running tests to determine the cause, but officials suspect higher-than-normal water temperatures played a role.

The die-off comes amid a summer of extreme heat across California that has included record ocean temperatures from San Diego to Los Angeles and beyond.

Warming water temperatures can alter the marine food chain in various ways — bringing about toxic algae that make crabs, for example, dangerous to eat. Researchers are also seeing more warm water animals, such as jellyfish and stingrays, off the coast.

Craig Sap, superintendent of California State Parks’ Angeles District, said Monday that it could take several days to confirm what led to the death of about 1,500 mullet and topsmelt fish that were discovered floating in the lagoon Thursday morning.

Officials said oxygen levels in the water tested normal, but the temperature in the lagoon was “significantly elevated” — about 82 degrees. Relentless summer heat and a lack of fog along the coast could have caused the temperature of the water to soar, Sap said.

“That temperature is probably beyond their tolerance level,” he said of the fish.

Although die-offs aren’t uncommon in lagoon environments, Sap said this was the largest he could recall in Malibu.

Upticks in ocean temperatures are normal in summer months, but what has been unusual is the level and spread of the increasing temperatures, said National Weather Service meteorologist Todd Hall.

This time of year, water around the Santa Monica Pier would normally be about 68 degrees. Monday afternoon, the temperature was 72 degrees. At Scripps Pier in La Jolla, temperatures are also typically about 68 degrees. Monday, the temperature was 77 degrees. Earlier this summer, that pier recorded its warmest water temperature reading in a century.

On average, waters have been about 5 degrees warmer than normal, and that's throughout coastal waters of Southern California, Hall said. [more]

More than 1,000 dead fish at Malibu Lagoon may be tied to record-warm ocean temperatures

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