SAN JOSE — San Francisco Bay waters are becoming clearer as the Gold Rush-era silt that clouded them is increasingly being swept to sea, but this new clarity is promoting a different problem: algae.
The U.S. Geological Survey tells The San Jose Mercury News that clearer water is allowing in more sunlight, which helps algae thrive.
The USGS says algae concentrations in the South Bay have increased 105 percent since 1993; in San Pablo Bay algae has increased by 72 percent.
Large algal islands on the water surface reduce oxygen levels, killing fish and other marine life.
The issue could prove costly for 42 sewage treatment plants around the bay if new regulations are adopted requiring the facilities to reduce nitrogen and phosphorus emissions, which feed algae.