Abstract Title

Session S-07E: Aquatic Vegetation

Presenter/Author Information

Brooke BannermanFollow

Keywords

Habitat

Start Date

1-5-2014 5:00 PM

End Date

1-5-2014 6:30 PM

Description

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.

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May 1st, 5:00 PM May 1st, 6:30 PM

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.