Copper Toxicity in the San Francisco Bay-Delta

San Francisco Bay has high dissolved copper concentrations—relative to nearby coastal waters—that often approach federal water quality standards put in place to protect sensitive marine life. But, how toxic is this copper? Previous studies by other researchers have suggested that metal-binding compounds known as ligands can “grab up” more than 99.9 percent of the total available dissolved copper in seawater, rendering that copper biologically unavailable. Microorganisms that need trace amounts of copper for growth cannot readily obtain it in its ligand-bound form