Lake San Antonio to reopen; cause of fish die-off remains unknown.

On Monday, July 22, the County of Monterey announced that Lake San Antonio, which the county Parks division closed on July 10, will reopen Wednesday, July 24 at 6am. The closure was related to a massive fish die-off, and out of precaution, county officials closed it a few days later so that the cause of the die-off could be investigated, and whether it could be a danger to people. 

Unfortunately, in a statement the county sent out today, the cause for the die-off, even after lab results, remains a mystery, and Bryan Flores, the County of Monterey’s Chief of Parks, thinks, like he did last week, that the cause is some sort of algae growth. 

It remains a hypothesis, but so far, that’s where the belief lies. The county’s statement reads, in part: 

“Based on the testing analysis and lack of conclusive evidence, the definitive reason for the fish die-off cannot be specifically determined. However, due to the fact that mammals and birds, such as wild pigs and turkey vultures, which consumed the dead fish did not die, that satellite imagery indicated the presence of an algae bloom, and water quality testing shows that the lake is normal for a surface water body, the prevailing belief is that dissolved oxygen levels in the water were low enough that the fish suffocated during the recent high heat wave event. As the algal bloom diminished, dissolved oxygen concentrations improved, and the fish die-off ceased.”

The same statement reads that the recent heat wave brought water temperatures as high as 90 degrees, “spurring on a rampant but short-lived algal bloom.”

Flores believes the die-off is due to the depleted oxygen levels in the lake brought on by the recent heat wave, but he’s not sure. But what he can say definitively is that the lake is not polluted with any toxins—experts don't believe that’s why any fish died, he says. 

Whether or not an algal bloom is the cause for the die-off off might forever remain a mystery—nature is full of them.