EPA Science Inventory

Has the rapidly expanding invasive dwarf eelgrass Zostera japonica in Yaquina estuary, Oregon impacted the distribution of native eelgrass Zostera marina – a critical intertidal habitat?

Citation:

Young, D., Pat Clinton, D. Specht, AND T. MochonCollura. Has the rapidly expanding invasive dwarf eelgrass Zostera japonica in Yaquina estuary, Oregon impacted the distribution of native eelgrass Zostera marina – a critical intertidal habitat? Presented at HMSC Seminar Series, Newport, OR, June 06, 2013.

Description:

Native eelgrass, Zostera marina, occupies a significant portion of marine-dominated intertidal and near-subtidal sectors of many coastal estuaries. In recent decades an invasive congener, Z. japonica, has become established in many Pacific Northwest estuaries. We measured the horizontal and vertical distributions of intertidal native and invasive eelgrass between 1997 and 2007 in Yaquina estuary using color-infrared aerial photography and digital classification to assess the impact, if any, of Z. japonica on Z. marina’s distribution. A bathymetric model was used to characterize the distribution of Z. marina and Z. japonica with intertidal elevation. Relative to Mean Lower Low Water, peak abundances of Z. marina and Z. japonica occurred at about 0.0 m and 1.5 m, respectively. Moreover, the two species seldom occupied the same bathymetric zone of a tidal flat. Although the areal extent of Z. japonica increased exponentially, and it now occupies a similar percentage of the intertidal zone as Z. marina, there has been no significant change in the areal extent of Z. marina over the study period.

Purpose/Objective:

This research project has demonstrated that, despite the exponential increase in the areal distribution of the invasive dwarf eelgrass Zostera japonica in lower Yaquina estuary between 1997 and 2007, there was no significant change in the areal distribution of the native eelgrass Z. marina there. Based upon classification of six annual color-infrared aerial photography surveys during that period, the Z. japonica habitat increased from about 10 to 70 hectars while the Z. marina habitat averaged about 90 hectars. However, an overlay of these distributions with modeled bathymetry of the lower estuary showed little overlap between the two congeners, with their abundance distributions peaking at about 1.5 m and 0.0 m, respectively (relative to the Mean Lower Low Water datum). Extensive field observations between 1997 and 2012 have shown that Z. japonica and Z. marina almost never co-occur in Yaquina estuary.

URLs/Downloads:

ABSTRACT - D YOUNG.PDF   (PDF,NA pp, 9.226 KB,  about PDF)

Record Details:

Record Type: DOCUMENT (PRESENTATION/ABSTRACT)
Start Date: 06/10/2013
Completion Date: 06/10/2013
Record Last Revised: 08/13/2014
Record Created: 06/10/2013
Record Released: 06/10/2013
OMB Category: Other
Record ID: 256520

Organization:

U.S. ENVIRONMENTAL PROTECTION AGENCY

OFFICE OF RESEARCH AND DEVELOPMENT

NATIONAL HEALTH AND ENVIRONMENTAL EFFECTS RESEARCH LAB

WESTERN ECOLOGY DIVISION

PACIFIC COASTAL ECOLOGY BRANCH