Abstract Title

Session S-07E: Aquatic Vegetation

Proposed Abstract Title

Zostera japonica and Z. marina: Do seasonal growth patterns of this native and non-native eelgrass differ when growing in an intermixed meadow in the Salish Sea?

Keywords

Habitat

Location

Room 6C

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 seasonal pattern of growth of these two species 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, about 63% of the intertidal area of the bay. 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 of submerged aquatic vegetation over the last 20 years, indicates that Z. japonica has expanded its range in Padilla Bay and is increasingly found intermixed with Z. marina. We measured vegetative characteristics monthly in more than 50 permanent plots—divided into predetermined vegetation cover zones—along a 4.3 km transect from shore to -2.6 m below MLLW. We found the two eelgrass species growing intermingled for more than 1 km along the transect. In the intermingled zones, density of Z. japonica was generally greater than Z. marina and height of Z. marina was greater than Z. japonica. Over the calendar year density of Z. marina was highest in January and decreased through the year while canopy height increased to a maximum in September/October. Density and canopy height of Z. japonica peaked in August. Biomass of both species peaked in July/August in all zones along the transect. Both species grew perennially with above and below ground biomass present throughout the year.

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

Zostera japonica and Z. marina: Do seasonal growth patterns of this native and non-native eelgrass differ when growing in an intermixed meadow in the Salish Sea?

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 seasonal pattern of growth of these two species 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, about 63% of the intertidal area of the bay. 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 of submerged aquatic vegetation over the last 20 years, indicates that Z. japonica has expanded its range in Padilla Bay and is increasingly found intermixed with Z. marina. We measured vegetative characteristics monthly in more than 50 permanent plots—divided into predetermined vegetation cover zones—along a 4.3 km transect from shore to -2.6 m below MLLW. We found the two eelgrass species growing intermingled for more than 1 km along the transect. In the intermingled zones, density of Z. japonica was generally greater than Z. marina and height of Z. marina was greater than Z. japonica. Over the calendar year density of Z. marina was highest in January and decreased through the year while canopy height increased to a maximum in September/October. Density and canopy height of Z. japonica peaked in August. Biomass of both species peaked in July/August in all zones along the transect. Both species grew perennially with above and below ground biomass present throughout the year.