Emerging Issues: Aquatic Nuisance Species
The introduction of non-native species has profoundly shifted Puget Sound's shoreline and marine ecology. Through such vectors as marine transportation, aquaculture, and intentional use of non-native plants, non-native species have spread through every corner of the Sound. When non-native species displace native species or cause damage to marine infrastructure, they become known as Aquatic Nuisance Species (ANS). ANS often spread aggressively through a combination of rapid growth, frequent reproduction, and a lack of natural predators, and can be very expensive and difficult to manage once introduced.
In the past several years, invasive tunicates Styela clava, Didemnum sp., and Ciona savignyi have made headlines in Puget Sound. These invasive sea squirts have shown a tendency to spread rapidly and blanket sub-tidal rocky substrates. They have also caused massive damage to shellfish growing operations in Canada and have fouled boats and marina structures from New Zealand to Hood Canal. Other species of concern in Washington state include the European Green Crab, a voracious predator that threatens native crabs and clams; the bamboo worm, which makes mudflats uninhabitable for oysters and displaces native benthic species; and the cordgrass spartina, which turns mudflats into saltmarsh and rapidly overgrows native grasses.
Volunteer scuba divers, Beach Watchers, and other interested citizens have proven effective in surveying for and monitoring ANS. To successfully eradicate unwanted invasive species, it is important to identify and locate invaders before they become firmly established. While luck will always play a role in early detection, the odds are dramatically improved with greater numbers of trained monitors.