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ZOSTERA MARINA IN A PACIFIC NORTHWEST ESTUARY: WHAT FACTORS CONTROL INTERTIDAL DISTRIBUTION?
Citation:
Boese, B L., B D. Robbins, AND G B. Thursby. ZOSTERA MARINA IN A PACIFIC NORTHWEST ESTUARY: WHAT FACTORS CONTROL INTERTIDAL DISTRIBUTION? Presented at 2001 Estuarine Research Federation meeting, St. Petersburg Beach, FL, November 4-8, 2001.
Description:
The impact of four factors (desiccation, macroalgae, erosion, light) on the distribution of Zostera marina was examined across tidal and bathymetric slope gradients. Data detailing seagrass characteristics, including 1 production, macroalgae biomass and sediment characteristics were collected monthly from 72 9m2 plots. Shoot number and canopy height were inversely related to tidal height and slope steepness. Reproduction occurred year-round, with most flowering in late summer and seedlings appearing in late winter. A greater percentage shoots were reproductive high in the intertidal, however, there was a greater total number of reproductive shoots low in the intertidal. Canopy height and shoot density were greatest in summer/fall with plants growing throughout the year. Tide height differences in leaf turnover rate may be related to summer abrasion by macroalgae and winter wave/currents. Sediment redox potential suggested that sediment H2S was not a controlling factor. Winter erosion appeared to limit the lower intertidal plants on steep slopes. Desiccation experiments showed that a 50% loss of wet wt inhibited blade recovery when rehydrated. High intertidal plants appeared to be light-adapted whereas low intertidal plants were dark-adapted. Our data suggest that the interaction of several different physical disturbances control the upper intertidal boundary for Z. marina.