<p>Identify ecosystem processes impacted; Z. japonica colonizes intertidal mud and sand flats that lack permanent macrophyte cover (Harrison and Bigley 1982, Posey 1988, Thom 1990, Larned 2003). The physical structure of the mid to upper intertidal zones is altered where Z. japonica occurs, often forming a dense, sod-like root matrix that may completely cover the substrate surface (Posey 1988). The narrow blades trap fine sediments. Posey (1988) documented that particle size was significantly smaller in Z. japonica patches after six years. Larned (2003) documented changes in nutrient fluxes in Oregon estuaries after invasion by Z. japonica. The data demonstrate that Z. japonica invasions alter water column benthos nutrient fluxes. These alterations may in turn affect pelagic primary production. These impacts are based on studies from Oregon and Washington as not much information is available specifically from California but it seems likely that similar impacts may be occurring in Humboldt Bay (reviewer comment).</p>

<p>Harrison and Bigley 1982, Larned 2003, Posey 1988, Thom 1990</p>

<p>Substrate particle size affects which invertebrates can inhabit the sediment and this change in invertebrate community structure can impact shorebird populations that feed on invertebrates (Quammen 1984, Baldwin and Lovvorn 1994b, Danufsky and Colwell 2003). A decrease in the burrowing ghost shrimp (Neotrypaea californiensis) and other large epifauna was found in areas of Z. japonica in Washington (Harrison 1987, Posey 1988). N. californiensis is a favored prey for the long-billed curlew and found in the diets of the marbled godwit and willet (Dr. Nils Wornock, pers. comm., Point Reyes Bird Observatory). As Nanozostera japonica covers mudflats that otherwise lack permanent macrophyte cover, it could reduce the foraging areas needed by shorebirds. The estuaries Z. japonica is invading are important migration and wintering grounds for many birds.</p>

<p>Baldwin and Lovvorn 1994b, CDFG 2009, Danufsky and Colwell 2003, Harrison 1987, Posey 1988, Quammen 1984</p>

<p>Often invades areas with little or no natural or human disturbance. A study conducted by Bando (2006) did show that Z. japonica displays a positive response to disturbance, which is particularly relevant to its invasion success, as tidal flats are dynamic systems that experience high levels of natural and anthropogenic disturbance, including bioturbation, coastal development, boating, shellfish culture, and in some regions (Washington), invasive smooth cordgrass (Spartina alterniflora) control.</p>

<p>Bando 2006</p>

<p>See information in question 2.2. Populations of the plant are expanding. A study by Shafer et al (2008) examined growth and productivity of Z. japonica at several points in its range on the Pacific Coast of North America and concluded that southern populations may be better adapted to warmer conditions than northern populations, suggesting that Z. japonica could expand further south in California.</p>

<p>Kirsten Ramey, California Department of Fish and Game, Shafer et al. 2008</p>

<p>Z. japonica likely arrived on the Pacific Coast of North America coincident with the introduction of oysters from Japan as packing material or as seed on oyster shell (Harrison and Bigley 1982). The introduction of Z japonica to Humboldt Bay was NOT likely associated with oyster culture, as oyster larvae imported here come from hatcheries. The method of introduction into Humboldt Bay is unknown. The detection of Z. japonica in Humboldt Bay, California, in June 2002 represents the first time this introduced species has been encountered in California. The method of spread around Humboldt Bay and to McNulty Slough is unknown, however, two locations of invasion have been at small public boat ramps which may suggest that plant material or seeds can be dispersed in mud stuck to boat hulls, boots and gear.</p>

<p>Kirsten Ramey, California Department of Fish and Game, CDFG 2009</p>

<p>Z. japonica was first detected in Washington in 1957 (Hitchcock et al. 1969), in British Columbia in 1969 (Harrison and Bigley 1982), and in Oregon in 1975 (Posey 1988). As an intertidal and subtidal plant, it is restricted to only one ecological type.</p>

<p>Harrison and Bigley 1982, Hitchcock et al. 1969, Posey 1988</p>

Z. japonica was discovered at the southwest end of Indian Island in Humboldt Bay, Humboldt County, California, in June 2002. In November 2006, Z. japonica was found near the Arcata Wastewater Treatment Plant in North Humboldt Bay. In March 2007, a fairly substantial population of Z. japonica at the Arcata Marsh, near the boat ramp at the foot of I Street in Arcata, CA, was found. In August 2007, a third new occurrence of Z. japonica growing on intertidal mudflats in Manila, CA, was discovered. On April 28, 2008, a new population of Z. japonica was discovered by a DFG crew in McNulty Slough in the Eel River estuary. McNulty Slough winds along the eastern boundary of the Department of Fish and Game Eel River Wildlife Area north of the mouth of the Eel River, Humboldt County, California. It inhabits mud flats between low and semi-high tide marks.

Kirsten Ramey, California Department of Fish and Game,