Seed density and distribution of non-native (Zostera japonica) and native (Z. marina) eelgrasses in sediments of mixed and mono-specific meadows
Presentation Abstract
The non-native eelgrass, Zostera japonica, is expanding its range in the Salish Sea and Willapa Bay and is increasingly found intermixed with the native eelgrass, Z. marina. We investigated the density and distribution of seeds of these two species in the sediments in intermixed and mono-specific stands in Padilla Bay, Washington. The native eelgrass, Z. marina, grows on extensive intertidal and subtidal flats in Padilla Bay, Washington covering more than 3000 hectares. The non-native eelgrass, Z. japonica, was unintentionally introduced to the Pacific Northwest in the early- to mid-1900’s. Z. japonica initially became established in Padilla Bay on high intertidal flats that had been bare of macro-vegetation. Mapping and ground truth investigations of eelgrasses over the last 20 years indicate that Z. japonica has expanded its range in Padilla Bay and is increasingly found intermixed with Z. marina. The two eelgrass species are growing intermingled for more than 1 km in transects from shore to lower edge of distribution in northern Padilla Bay. In November 2013, we collected sediment cores from 56 sample sites extending from the high tide limit to about -1.0 m below MLLW (a 3.3 km extent). Sediment samples were enumerated for seeds and a subset was tested for viability using an adaptation of the tetrazolium chloride test. Density of Z. japonica seeds was much higher than density of Z. marina seeds in the intermixed meadows. Seed densities were highest in areas of highest plant density. Lower seed densities were found in areas distant from seed sources.
Session Title
Session S-07E: Aquatic Vegetation
Conference Track
Habitat
Conference Name
Salish Sea Ecosystem Conference (2014 : Seattle, Wash.)
Document Type
Event
Start Date
1-5-2014 5:00 PM
End Date
1-5-2014 6:30 PM
Location
Room 6C
Genre/Form
conference proceedings; presentations (communicative events)
Contributing Repository
Digital content made available by University Archives, Heritage Resources, Western Libraries, Western Washington University.
Subjects – Topical (LCSH)
Dwarf eelgrass--Seeds--Washington (State)--Padilla Bay; Zostera marina--Seeds--Washington (State)--Padilla Bay; Invasive plants--Washington (State)--Padilla Bay; Plant competition--Washington (State)--Padilla Bay
Geographic Coverage
Salish Sea (B.C. and Wash.); Padilla Bay (Wash.)
Rights
This resource is displayed for educational purposes only and may be subject to U.S. and international copyright laws. For more information about rights or obtaining copies of this resource, please contact University Archives, Heritage Resources, Western Libraries, Western Washington University, Bellingham, WA 98225-9103, USA (360-650-7534; heritage.resources@wwu.edu) and refer to the collection name and identifier. Any materials cited must be attributed to the Salish Sea Ecosystem Conference Records, University Archives, Heritage Resources, Western Libraries, Western Washington University.
Type
Text
Language
English
Format
application/pdf
Seed density and distribution of non-native (Zostera japonica) and native (Z. marina) eelgrasses in sediments of mixed and mono-specific meadows
Room 6C
The non-native eelgrass, Zostera japonica, is expanding its range in the Salish Sea and Willapa Bay and is increasingly found intermixed with the native eelgrass, Z. marina. We investigated the density and distribution of seeds of these two species in the sediments in intermixed and mono-specific stands in Padilla Bay, Washington. The native eelgrass, Z. marina, grows on extensive intertidal and subtidal flats in Padilla Bay, Washington covering more than 3000 hectares. The non-native eelgrass, Z. japonica, was unintentionally introduced to the Pacific Northwest in the early- to mid-1900’s. Z. japonica initially became established in Padilla Bay on high intertidal flats that had been bare of macro-vegetation. Mapping and ground truth investigations of eelgrasses over the last 20 years indicate that Z. japonica has expanded its range in Padilla Bay and is increasingly found intermixed with Z. marina. The two eelgrass species are growing intermingled for more than 1 km in transects from shore to lower edge of distribution in northern Padilla Bay. In November 2013, we collected sediment cores from 56 sample sites extending from the high tide limit to about -1.0 m below MLLW (a 3.3 km extent). Sediment samples were enumerated for seeds and a subset was tested for viability using an adaptation of the tetrazolium chloride test. Density of Z. japonica seeds was much higher than density of Z. marina seeds in the intermixed meadows. Seed densities were highest in areas of highest plant density. Lower seed densities were found in areas distant from seed sources.
