As recently as last year, San Diego Bay had the dubious honor of hosting the only two identified Australian sea squirt infestations along the length of the West Coast.
According to Sarah Cohen, a San Francisco State University marine biologist researching the aquatic plant under a grant from California Sea Grant, no one has yet determined whether the new discovery indicates that the soggy lichen-appearing organism is spreading rapidly or whether researchers are sampling waterways more intensively.
What is clear is that this new invasive species has the potential to damage waterways, water distribution systems and aquaculture by gradually blocking water intake and outflow pipes and valves. The consequent environmental damage is not immediately obvious, but becomes apparent as the species develops sufficiently large breeding colonies.
The rapidly reproducing sea squirts, or tunicates, invaded Prince Edward Island off the east coast of Canada. There they caused the most harm to shellfish producers because they attach themselves to bivalves and shellfish nets, explained researcher Gregory Ruiz of the Smithsonian Environmental Research Center in Edgewater, Md., in an article on the California Sea Grant College website. How the tunicate invasion will affect San Diego is not yet known, but invasive species create problems to ecosystems because of their lack of natural predators.
“An invasive species is any creature taken from its home and its enemies and put in a new environment with no natural enemies to control them,” explained Leigh Taylor Johnson, a marine advisor with the University of California Cooperative Extension Sea Grant Extension Program. “They are able to grow almost unchecked. That gives them a big competitive edge over native species and upsets the balance of nature,” she added.
Johnson said that researchers speculate that sea squirts arrived in the U.S. in oceangoing ships’ sea chests — openings in a vessel’s hull encasing engine cooling intake pipes – and then are spread, like other invasive species that adhere to hulls, by small recreational boats that are trailered between lakes and rivers.
Previous invasions of foreign aquatic species such as the freshwater Quagga and Zebra mussels have caused extensive damage to American waterways and water and irrigation systems. Both were introduced into the United States, probably through discharge of ships’ ballast water, in the late 1980s and have now spread throughout the West, adversely affecting reservoirs, dams, lakes and recreational boating and fishing.
The Zebra mussels, through the build-up of their concrete-like excretions, blocked municipal water and power plant cooling water intake systems that drew their supply from infected lakes and rivers, particularly from the Great Lakes, where the Zebra mussels were first introduced into the U.S.
Clearing the blockages cost system operators millions of dollars.
The tiny Quaggas are a particular concern, she explained, because their shells are dangerously sharp and they attach themselves in dense clusters and clog water pipes of all varieties.
“Quaggas cause fouling issues and are voracious feeders. They’re eating up all the food and native species can’t get enough to eat, causing a problem for fishermen,” Johnson said.
They also cause problems for farmers and ranchers, too, she said, since they invaded agricultural drip watering systems in Imperial County and may threaten the salmon spawning areas in the Northwest. Once Quagga larvae invade the water supply system it can cost millions of dollars to eradicate the invaders.
While no currently known saltwater invasive species is quite as damaging as the Quagga or Zebra mussel, she explained, some saltwater invasives are actually carriers of harmful diseases.
A key tool in the effort to halt the spread of invasive aquatic species involves an aggressive campaign to educate and require owners of trailerable boats to clean their boats, trailers, vehicles, fishing and recreational equipment — and even clothing, footwear and pets that have been in contact with freshwater lakes or rivers — after each use and before transporting the boats to a new waterway which may not be infected.
Since state and federal law have now made transportation of Quagga and Zebra mussels illegal, the California Department of Fish and Game (DFG) has developed a set of recommendations for boat owners for cleaning boats to prevent the spread of invasive species.
The guide to boat cleaning, titled “Don’t Move a Mussel,” is available on online.
If a boat is found to be contaminated, DFG can quarantine the boat and fine the owner.
Owners of larger vessels kept in marinas are advised to use appropriate anti-fouling paints on their hull bottoms and follow recommended hull maintenance procedures, which include cleaning every three to four weeks.
Scott MacLaggan, marina manager of Sunroad Marina on Harbor Island, who follows environmental management issues closely, agreed that the larger vessels are not the culprit in spreading invasive species but rather the trailerable boats that travel from lake to lake.
“The boats we have here don’t travel between (lakes). The boatyards clean them thoroughly,” he said, and most owners have their hulls scrubbed by divers every few weeks.
“If you’re just sitting in place, you’re not adding anything new, but you don’t want to pass (invasive species) along or bring it back,” Johnson said.
For more information about invasive species and their impact on the environment, visit California Sea Grant’s website at www-csgc.ucsd.edu (click on special topics) and DFG’s website at www.dfg.ca.gov/invasives. For cleaning guidelines, visit www.dfg.ca.gov/invasives/quaggamussel.