The recent discovery of a new type of invasive mussel in the Sacramento-San Joaquin River Delta is raising concerns that the non-native species could cause major ecological harm and inflict costly complications for the infrastructure California relies on to deliver water across the state.
State workers discovered golden mussels attached to equipment and buoys in the Port of Stockton last month while carrying out routine water quality tests. The mussels were also recently found in O’Neill Forebay, part of the state’s water delivery system south of the Delta near Santa Nella.
“Any invasive species in our Delta is problematic, and we’re going to do everything we can to control its spread,†said Steve Gonzalez, a spokesperson for the California Department of Fish and Wildlife.
Golden mussels, an invasive species that officials across the country have been worried about for years, invaded North America for the first time through the Port of Stockton.
The department announced the discovery last week, saying it’s the first time golden mussels have been found in North America. Native to rivers and creeks in China and Southeast Asia, the bivalves have appeared in waterways elsewhere in Asia as well as South American countries, including Brazil, Argentina, Uruguay and Paraguay.
The species has colonized new regions when transported on ships’ hulls or in ballast water that is drained in ports.
The mussels can compromise water delivery systems by encrusting screens and filters, attaching to the walls of large pipelines, and clogging smaller pipes.
The effects for the state’s water infrastructure could be similar to the complications that have been caused by an invasion of quagga mussels in the Colorado River’s reservoirs. Since their discovery in Lake Mead in 2007, those mussels have spread throughout aqueducts and reservoirs in Southern California.
After finding the golden mussels in O’Neill Forebay, state workers have begun surveys to determine the extent of the infestation in the State Water Project system, including the California Aqueduct, which transports water pumped from the Delta to cities and farmlands.
The increased monitoring and maintenance that will be required is expected to have an economic impact for the State Water Project, increasing water delivery costs, said Tanya Veldhuizen, manager of the Department of Water Resources’ Special Projects Section.
The estuary already has a long list of non-native species, including bass, water hyacinth, Asian clams and overbite clams. But golden mussels could be particularly problematic for water infrastructure and the Delta’s ecosystem if the species spreads and flourishes, said Andrew Rypel, a professor of fish ecology and director of UC Davis’ Center for Watershed Sciences.
“It’s a major threat,†Rypel said. “They’re very difficult to control once they’re established.â€
The Biden administration and California are close to finishing new plans for operating the state’s major water systems, an overhaul that is generating debate.
Where the mussels attach and grow, they can create problems for all sorts of infrastructure, including docks and water intakes, requiring costly efforts to remove them.
“It can create this major cost that simply has to be dealt with, just for you to effectively run your infrastructure,†Rypel said.
Where the mussels take root, Rypel said, there are different methods of removing them: mechanically scraping them off, treating them with chemicals, or treating them with a certain dead bacteria that kill them — a controversial method because of concerns about potential ecological effects.
If the mussels thrive in the Delta, they could dramatically alter the ecosystem, Rypel said. Their larvae swim and spread out in the water, colonizing solid surfaces and attaching themselves with fibers. The mollusks are efficient filter feeders and can increase the clarity of water by consuming large quantities of plankton, which native fish and other creatures depend on.
“It could completely change the ecosystem, in a worst-case scenario, completely clarify the water, leaving less food for salmon and native fish,†Rypel said. “That’s the ecological problem that people will be concerned about.â€
The changes in the Great Lakes since the 1990s show how severely an ecosystem can be upended by an invasion of non-native mussels, Rypel said. There, zebra mussels and quagga mussels have thrived and caused a major decline in the yellow perch fishery.
In California’s Delta, there are threatened and endangered fish species, including steelhead trout, two types of Chinook salmon, longfin smelt, Delta smelt and green sturgeon.
If the golden mussels take hold and dominate the ecosystem, Rypel said, that would mean less food resources for those native species. The non-native mussels also could kill native mussels in the estuary.
“I think we want to do as much as we can to prevent that kind of a scenario, but it’s going to be a challenge,†Rypel said.
Longfin smelt have suffered major declines in the San Francisco Bay estuary. Now the federal government has declared the fish an endangered species.
He said the serious threats call for an aggressive, coordinated effort to contain and remove the mussels, and to prevent them from spreading to new areas.
To contain the mussels as much as possible, state officials are urging Californians to be sure to clean, drain and dry all boats and equipment when removed from a water body. They say this strategy has helped prevent the further spread of quagga mussels and zebra mussels beyond the lakes and waterways those species have colonized.
The state Department of Water Resources has since 2007 had a program in place to monitor for the presence of zebra and quagga mussels at various locations in the Delta and throughout the State Water Project. The department has now expanded its monitoring to check for golden mussels, Veldhuizen said, and is also adopting other measures to protect pumping plants and reduce potential effects on water deliveries.
California State Parks officials have begun additional exit inspections of boats at O’Neill Forebay, San Luis Reservoir and Los Banos Creek Reservoir to ensure all water is drained from livewells, bilges and outboard motors to prevent the spread of the mussels.
“We’re asking the public to do the same thing that they do for quagga and zebra, and clean, drain and dry their watercraft and equipment every time they go to a different water body in the state,†Gonzalez said. “It’s important for all of us to pitch in on this.â€
