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Massive California Fish Kill Connected to Hypoxia and Toxic Algae

An NCCOS-administered study at the University of Southern California (USC) found a potential link between harmful algal blooms and hypoxia as the cause of a massive fish kill. On 8 March 2011, millions of dead fish (mostly Pacific sardine) were observed in King Harbor in the City of Redondo Beach, California. Through support from NCCOS’ Monitoring and Event Response for Harmful Algal Blooms (MERHAB) Program, the USC research group has been monitoring this area of recurrent algal blooms since 2006.

The USC team’s observations indicated that the immediate cause of the fish kill was depletion of dissolved oxygen, probably related to an influx of hypoxic coastal water. However, the group continues to investigate why the massive school of fish entered the harbor. Analyses of fish gut contents tested positive for the powerful algal neurotoxin, domoic acid, and algae collected from the nearshore coastal ocean had very high concentrations of the toxin. The findings support the idea that the fish ingested the toxin in coastal waters before entering the harbor. It is unclear at this time if ingestion of the toxin may have exacerbated the physiological stress brought on by hypoxia.

The results support the development of forecast models to provide early warnings and enhance response capabilities to mitigate the effects of domoic acid, which causes a number of neurological disorders, and death, in animals and humans that consume contaminated fish.

For more information, contact Marc Suddleson at

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