Synonyms: Nanozostera japonica (Asch. & Graebn.) P. Toml. & U. Posl.
Common names: dwarf eelgrass; Japanese eelgrass
Zostera japonica (=Nanozostera japonica, dwarf eelgrass) is an aquatic plant that forms dense stands in shallow, sheltered bays and estuaries. Populations of Z. japonica have been found in Humboldt County. Z. japonica often invades areas with little or no natural or human disturbance and also shows a positive relationship with disturbance. Z. japonica lives as an annual, overwintering as buried seeds, or a short-lived perennial. It reproduces vegetatively through rhizomatous cloning and sexually through seed production. The dispersal of the seeds, both within and between estuaries, may be aided by waterfowl species. Z. japonica has been shown to rapidly expand in the spring and summer.
High – These species have severe ecological impacts on physical processes, plant and animal communities, and vegetation structure. Their reproductive biology and other attributes are conducive to moderate to high rates of dispersal and establishment. Most are widely distributed ecologically.
Moderate – These species have substantial and apparent-but generally not severe-ecological impacts on physical processes, plant and animal communities, and vegetation structure. Their reproductive biology and other attributes are conducive to moderate to high rates of dispersal, though establishment is generally dependent upon ecological disturbance. Ecological amplitude and distribution may range from limited to widespread.
Limited – These species are invasive but their ecological impacts are minor on a statewide level or there was not enough information to justify a higher score. Their reproductive biology and other attributes result in low to moderate rates of invasiveness. Ecological amplitude and distribution are generally limited, but these species may be locally persistent and problematic.
Alert – An Alert is listed on species with High or Moderate impacts that have limited distribution in California, but may have the potential to spread much further.
Watch – These species have been assessed as posing a high risk of becoming invasive in the future in California.
A – A pest of known economic or environmental detriment and is either not known to be established in California or it is present in a limited distribution that allows for the possibility of eradication or successful containment.
B – A pest of known economic or environmental detriment and, if present in California, it is of limited distribution.
C – A pest of known economic or environmental detriment and, if present in California, it is usually widespread.
D – An organism known to be of little or no economic or environmental detriment, to have an extremely low likelihood of weediness, or is known to be a parasite or predator.
Q – An organism or disorder suspected to be of economic or environmental detriment, but whose status is uncertain because of incomplete identification or inadequate information.
* – An asterisk next to the rating indicates that a plant is included in the CCR Section 4500 list of California State Noxious Weeds.
-* – This plant is included in the CCR Section 4500 list of California State Noxious Weeds, but is otherwise not rated.
Plant Assessment Form - Information gathered by Cal-IPC on the impacts, rate of spread, and distribution of invasive plants in California. Does not include management information.
Weed Management Notes
No Weed RIC Management Notes are available for this species. Check for information on other species in the genus on the Weed RIC site.
Cal-IPC Newsletter Articles
There are no newsletter articles associated with this species yet.
Cal-IPC Symposium Presentations
Presentations are linked where available. Where a presentation is not available, find more information by reading the abstract in the Cal-IPC Symposia Archive.
There are no Symposium presentations associated with this species yet.
Other Zostera japonica Information
Calflora - Distribution map and records of this species in California.
CalWeedMapper - Distribution map of this species in California with ability to determine regional priorities.
EDDMapS - Distribution of this species in North America.
Jepson Interchange - Information on this plant's taxonomy, biology, and distribution from UC Berkeley's Jepson Herbarium.
USDA PLANTS Database - Information on identification and distribution, with links to websites in individual states.
