San francisco bay invasive spartina

The large expanse of Spartina at the mouth of Jacoby Creek established after , colonizing newly deposited sediment from the creek. Ground photos document the continued spread of the species after in many sites around Humboldt Bay. This detailed mapping project Pickart ; 5.

The Mad River Slough at the north end of Humboldt Bay had the greatest proportion of salt marsh with respect to bay acres, the least severe Spartina invasion based on both the percent of total salt marsh invaded and the proportion of salt marsh in low vs. Between and refuge staff completed an updated inventory of all Spartina within its boundaries Grazul and Rowland ; 3. Much of the brackish marsh on the refuge is behind dikes, which limits tidal dispersal of seed to overtopping tides or failing tidegates.

Mapping was expanded to all three estuaries Humboldt Bay, Mad River, Eel River in using more generalized cover classes and relying more on photointerpretation Grazul and Rowland Clearly the invasion is still in progress. Results to date demonstrate that Spartina densiflora has a large seedbank that persists up to 3 years, with substantial reduction in the size of the seedbank by the third year. After observing an increase in the size of the stand from to almost 5, sq ft over a 3-year period, the California DFG eradicated the stand by diking the area, cutting the grass, applying salt and covering it with black plastic.

This timely intervention prevented the massive invasions that have occurred in San Francisco and Willapa Bays. Unfortunately, a similar early detection and response strategy was not possible with the long-established Spartina densiflora. However, its continued spread in Humboldt Bay, and its availability as a source to other west coast estuaries, justifies a timely response to this invasion. Salt marsh occupied approximately 9, acres around Humboldt Bay prior to Euro-American contact Pickart Similar losses to salt marshes have occurred in all estuaries in California.

The species composition of salt marshes is strongly controlled by the influence of tides. Salt marsh vegetation can only become established at or above the Mean Lower High Water level the average of the lower of two daily high tides. Low marsh is overwhelmingly influenced by the duration of salt water inundation.

Both salinity and lack of oxygen during submersion limit plant life to only the most stress tolerant of species. In Humboldt Bay, salt marshes were classified by Eicher ; 37MB pdf : into three types based on their elevation, with corresponding differences in vegetation. The lowest elevation marshes, are dominated by pickleweed Salicornia pacifica. At these elevations, pickleweed forms homogeneous stands known as Pickleweed Marsh.

In our native salt marshes, pickleweed, a hardy colonizer, is the first plant to establish in a newly forming marsh. Although Eicher's study characterized middle elevation marsh as Spartina Marsh, Spartina has since been documented as spreading into our lowest elevation marshes and displacing Pickleweed Marsh.

In Humboldt Bay, saltmarshes occur both as islands and adjacent to the mainland. Island marshes have no freshwater input other than rainfall, so salinity is high and limiting.

Mainland marshes often receive freshwater runoff that can dilute salinities, resulting jn brackish marshes at the upper edge of salt marshes. Spartina densiflora appears to flourish in our brackish marshes, as it does in its native range and in other countries where it has invaded. Cordgrass displaces pickleweed Salicornia pacifica in low and mid-elevation marsh. In restored marsh where S. Where freshwater influences are present through streams or seeps entering the marsh, Spartina outcompetes seaside arrow-grass, sea milkwort Glaux maritima , western grasswort Lilaeopsis occidentalis and other native brackish species.

It is unknown what the ultimate extent of the cordgrass invasion could be if it is not controlled. In Spain, which has also undergone a major invasion by dense-flowered cordgrass, the species has spread beyond intertidal environments to occupy extensive areas of terrestrial habitats Bortolus In Humboldt County, Spartina densiflora can be found not only in salt marshes, but in brackish marshes, along slightly brackish river channels, on sandy substrates in dune wetlands, on rocky substrates along dikes, and colonizing bare mudflats.

Studies show that cordgrass invasion has a dramatic impact on both terrestrial and intertidal invertebrates. Mitchell K pdf , Mitchell K pdf compared invaded with restored marsh, measuring both abundance and diversity of above-ground invertebrates.

Two years after Spartina removal was initiated, restored marsh had dramatically higher abundance and diversity as measured at the order level of invertebrates than the invaded site. Although Spartina plants are taller and offer more refuge from high tides, they are structurally less complex than native vegetation and reduce the opportunity for diversity of invertebrate consumer strategies.

The invaded marsh favored mosquitoes, a trend also observed at invaded salt marshes in Spain. Recent research Mitchell measured a trophic shift in terrestrial salt marsh invertebrates, resulting in increased cellulose consumers in invaded marshes. The presence of emergent vegetation at high tides shifted arachnid predation from active to ambush tactics. Higher abundance of the Talitrid amphipod, Orchestia , an important prey for higher organisms was found in restored marshes.

Recent research indicates that Spartina densiflora has a negative impact on estuarine productivity Lagarde ; K pdf. These results suggest that the turnover or herbivory rates of the native autotrophs vascular plants and algae are higher than those of S. Monitoring of past restoration has shown that nonvascular plant diversity and abundance increases after removal of S. Cordgrass colonizes areas opened to tidal influence, making it much more difficult for restoration projects in the region to establish indigenous salt marsh vegetation.

Cordgrass is usually the first species to colonize in bare areas created when new tidal flow kills off existing fresh or brackish vegetation. Many people in the region question the value of tidal marsh restoration projects because of the threat of cordgrass colonization. In addition to its impacts locally, cordgrass in the Humboldt Bay region threatens to colonize other west coast estuaries via ocean dispersal of its seeds, as demonstrated by the preliminary results of a drift card 88K pdf study carried out by Portland State University.

Drift cards from Humboldt Bay in and were found within a month of their release in numerous locations along the Oregon Coast, as well as in southwest Washington. Spartina densiflora control and salt marsh restoration in Humboldt Bay. Spartina on a mid- to high-elevation marsh in the Mad River Slough was mowed repeatedly in square-meter plots using a weed-whip.

After two years, all Spartina plants were killed compared with minor Spartina cover reduction in control plots , and native plants had recolonized in many areas.

No Spartina recruited from seed during this time. Following this success, a acre mainland salt marsh was restored, with combined funding from the Conservancy and the FWS, beginning in Fall Depending on how deeply the treatment is applied, mortality can be achieved in a few visits.

However, in the first year following treatment, seedling flushes may occurr on resulting bare areas on the mainland marsh where freshwater input is abundant, necessitating follow-up treatments using flaming or brushcutting. Seedlings can emerge both from the persistent seedbank or by seeds newly dispersed from nearby areas.

The latter possibility emphasizes the need for a regional approach to eradication, in which seed production is entirely halted. Research has confirmed that the seedbank persists for at least 3 years. The pilot restoration begun in resulted in a highly functioning salt marsh with increased diversity of algae, vascular plants, and invertebrates.

Revegetation was explored, but determined to be unnecessary. Native marsh vegetation achieved full recovery, although removal of newly established seedlings will be required until regional eradication cuts off seeds sources Pickart ; 5. Restoration resulted in the dramatic recovery of two rare salt marsh plants, Humboldt Bay owl's clover Castilleja ambigua ssp.

The brackish marshes had been highly invaded by Spartina, which is much taller and blocks more light thean the native hosts of these rare species. Following Spartina removal, the population of Humboldt Bay owl's clover increased from a mean of 1, to approximately , Beginning in July , crews were deployed throughout the refuge over a total of more than acres of salt and brackish marsh.

In addition to the baseline mapping discussed above, permanent monitoring plots were established throughout the site to measure progress. Work is concentrated in summer months due to favorable tides and weather, but continues through the winter. The primary control method is the use of brushcutters, but manual removal especially on rocky substrates like dikes and heavy equipment have also been employed.

The latter has been used to remove dense stands on the refuge that can be reached from the dike or are otherwise accessible. Of the remaining Spartina , a large portion is on the Eureka Slough Unit, a highly invaded medium elevation marsh.

Given the labor-intensiveness of this site, for mechanical removal, experimental mowing followed by rototilling using an amphibious tractor Marshmaster was carried out. This method was very efficient and is planned for the remainder of the Eureka Slough in spring Picture: An equipment operator maneuvers a Marshmaster to cut S. Given the expected sea level rise associated with climate change, the investment in Spartina removal and salt marsh restoration has been questioned by some.

Two issues related to Spartina and sea level rise are addressed below. A universal call has been made to eradicate the invasive lionfish, and some surprisingly entertaining and unconventional methods top off the list. Lionfish derbies are being held, where fishermen and divers compete to catch the ravenous invasive, and an "Eat Lionfish" campaign has emerged to encourage a market for the flavorful fish.

Also called the red-bellied harvest mouse. Also called smooth cordgrass or saltmarsh cordgrass. The audio, illustrations, photos, and videos are credited beneath the media asset, except for promotional images, which generally link to another page that contains the media credit.

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Any interactives on this page can only be played while you are visiting our website. You cannot download interactives. An invasive species is an organism that is not native to an ecosystem, and thus has no natural predators in that environment. This lack of predators often causes some wicked problems in the place it colonizes. With no predators, these invaders can out-compete local fauna and flora, and then disrupt the balance of the ecosystem. You might be wondering, how do these species get to their new location?

Well, some are introduced purposely by humans, such as the European hare which was brought to Australia in the s, and some are introduced by accident, like the emerald ash borer, which has wiped out native ash trees in the Midwest and the Eastern United States.

Explore the new worlds of these alien species with this collection of resources. An invasive species is an organism that is not indigenous, or native, to a particular area.

Invasive species can cause great economic and environmental harm to the new area. Invasive species—organisms not native to a particular area—are one of the leading causes of global biodiversity loss, and humans are the reason why.

Join our community of educators and receive the latest information on National Geographic's resources for you and your students. Skip to content. Twitter Facebook Pinterest Google Classroom. Article Vocabulary. Spartina alterniflora grows out from the coast into the water. Army Corps of Engineers. Bay Area. California clapper rail.