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DESICCATION AND OTHER FACTORS AFFECTING THE UPPER INTERTIDAL DISTRIBUTION OF EELGRASS IN YAQUINA BAY, OR
Citation:
Boese, B L. DESICCATION AND OTHER FACTORS AFFECTING THE UPPER INTERTIDAL DISTRIBUTION OF EELGRASS IN YAQUINA BAY, OR. Presented at Pacific Estuarine Research Society annual meeting, Portland, OR, May 2-4, 2002.
Description:
Eelgrass (Zostera marina) in Pacific Northwest is primarily intertidal, yet little research has been done on what factors control its upper intertidal growth boundary. In July 2000 a two year study was initiated in Yaquina Bay (Newport, OR) to evaluate the effects of four factors (light, macroalgae, erosion, and aerial exposure) on Z. marina density and morphology. Although all four factors may play a role in limiting Z. marina, at present, exposure to desiccating conditions appears to be most important. Blade damage resulting from desiccation is common and distinct from other damage morphologies, leading to the development of a quantitative desiccation damage index. This index was then used to compare the amount of damage in Z. marina across intertidal bathymetric slopes (steep and shallow) and across intertidal tide height gradients. Results suggest that higher intertidal plants have more desiccation damage than those growing lower in the intertidal and that blades tend to break at damage points, which may partially explain why high intertidal plants have shorter canopies. No effect of bathymetric slope on the desiccation index was observed. Recent improvements of this index using digital color IR photography will be discussed.