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The Spartina Watch ProgramContact InformationVanessa Howard IntroductionFour species of Spartina, commonly known as cordgrasses, are exotic, invasive plants in estuaries of the west coast of North America. These grasses were originally brought to the west coast both intentionally, with the purpose of erosion control and forage production, and unintentionally - hitching rides in ship’s ballast water or in oyster packing material. However, over the past few decades, people have recognized the threats posed by these rapidly spreading plants. Invasive cordgrasses can clog flood channels, displace native vegetation, significantly raise mudflat elevation, and reduce habitat of Dungeness crab, shorebirds and migratory waterfowl by trapping sediments with their dense stems and root-mats. One species of cordgrass is native to the west coast - Spartina foliosa. It is historically found in salt marshes from Baja California, Mexico to Bodega Bay in California. This native plant has formed a fertile hybrid with the invasive S. alterniflora. This hybrid is of particular concern in the San Francisco Bay where it threatens to displace habitat normally occupied by S. foliosa.
Spartina Dispersal Study - Drift Card ReleaseGoal: To identify frequent deposition locations of plant material exiting currently infested bays. This will help us to refine and prioritize early detection surveys. Method: Monthly releases of two-hundred bright-yellow drift cards have been completed from the mouths of three estuaries: Willapa Bay, WA and Humboldt and San Francisco Bays in California. These estuaries are known to have significant populations of one or more Spartina species and are therefore potential sources of seeds or plant fragments.
Releases took place between September 2004 and August 2005. Each releases was completed within two hours of high-tide to ensure the cards were pulled out into the open ocean. The biodegradable wooden drift cards (see photo above) are designed to float on the water surface and be carried by the ocean currents, behaving much as seeds or plant fragments would. The cards, made of lightweight plywood and painted with non-toxic paint, are only designed to persist for a few months in the harsh conditions of the ocean. But in that short time, they have the potential of revealing a wealth of information. Releases were done with the generous collaboration of the Washington Department of Fish & Wildlife, the U.S. Fish & Wildlife Service - Arcata Office, and the Golden Gate National Recreation Area.
Have you found a drift card?In addition to our study, there are now two additional drift card studies being conducted in Puget Sound, Washington and in the San Francisco Bay area, looking at localized drift patterns. Even though our last release was in 2005, there's still a chance you'll find a card... if you do, please pick it up and contact us with the card number (#20409, for example); when and where you found the card; your contact information (in case we have a follow up question or can't understand your message for some reason) PLEASE DO NOT THROW THE CARDS BACK IN THE WATER! PLEASE DO NOT LEAVE THEM ON THE BEACH! Frequently asked questions (pdf format) Contact us at: Phone: (503) 725-2937 or Email: spartinawatch@pdx.edu Drift Card Recovery MapsTo see better detail in any of the three maps below, just right click and select 'View Image'.
Photographs
Rhizome ViabilityCommonly used mechanical control methods for Spartina alterniflora involve varying levels of disturbance to rhizomes and roots. We examined the viability of rhizome fragments and their potential role in dispersal. Production of rhizome fragments by rototilling in Willapa Bay, Washington was studied. The top 10 cm of the sediment contained an average of 310 fragments/meter2. Median rhizome length was 3.7 cm. Eighty-seven percent of the rhizome fragments had at least one vegetative shoot attached. Survivorship of S. alterniflora rhizome fragments from Willapa Bay and San Francisco Bay populations was investigated using a three-way factorial design. Treatments included two fragment sizes, approximating those found in Willapa Bay, immersed in freshwater, 15 ppt or 35 ppt saltwater for 3, 8 or 15 days. Fragments were then individually planted and grown in greenhouse ponds for four months. Rhizome survivorship was low (8.6% or less) in all 35 ppt treatments. Survivorship was 37.3 and 87.5% in 15 ppt and freshwater treatments, respectively. Large rhizomes had higher survivorship than small rhizomes at all salinities. The length of time the rhizome fragments were immersed prior to planting had variable effect on survivorship. Results suggest rototilling for control of Spartina may spread the infestation within an estuary but is unlikely to result in spread to other estuaries by ocean transport. Thus, tilling should be used with caution in estuaries with small, isolated populations of Spartina. FRAGMENT PROPAGULES OF SPARTINA ALTERNIFLORA & POTENTIAL EASTERN PACIFIC DISPERSAL (pdf format) Additional Information & LinksKeys & Brochures
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