Abstract Title

Session S-07E: Aquatic Vegetation

Presenter/Author Information

Michael HannamFollow

Keywords

Habitat

Start Date

1-5-2014 5:00 PM

End Date

1-5-2014 6:30 PM

Description

Physical and biotic factors can influence the distribution of species at multiple scales, and are thus important when predicting invasive species impacts. I examined the influence of physical context and congener presence on variability the vertical zonation of an invasive seagrass, Z. japonica and its native congener Z. marina. Nearshore intertidal topography, hydrodynamic exposure, and tidal range were examined as abiotic predictors of the deep extents of Z. japonica and Z. marina, the shallow extent of Z. marina and the elevation overlap of the two species, both at within site and among site spatial scales. Z. marina’s extended to higher elevations at transects that were less rough, more gently-sloped, less wave exposed, and in the presence of Z. japonica. Site-scale rugosity was the best predictor of site scale shallow extent of Z. marina. Z. japonica deep extent was explained by Z. marina shallow extent at both spatial scales, and also by rugosity when examining site-averaged patterns. Overlap of the two species along a transect was poorly predicted by physical context, but site-averaged range overlap was greater where depth profiles were more linear. Bottom profile complexity was the most consistently important predictor studied, confirming the importance of the geomorphic template on the zonation of these species. Furthermore, these findings suggest a greater sensitivity of Z. marina shallow extent to physical factors, and a greater sensitivity of Z. japonica deep extent to biotic factors.

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

Broad-Scale Environmental Predictors of Intertidal Zonation of Z. japonica and Z. marina

Room 6C

Physical and biotic factors can influence the distribution of species at multiple scales, and are thus important when predicting invasive species impacts. I examined the influence of physical context and congener presence on variability the vertical zonation of an invasive seagrass, Z. japonica and its native congener Z. marina. Nearshore intertidal topography, hydrodynamic exposure, and tidal range were examined as abiotic predictors of the deep extents of Z. japonica and Z. marina, the shallow extent of Z. marina and the elevation overlap of the two species, both at within site and among site spatial scales. Z. marina’s extended to higher elevations at transects that were less rough, more gently-sloped, less wave exposed, and in the presence of Z. japonica. Site-scale rugosity was the best predictor of site scale shallow extent of Z. marina. Z. japonica deep extent was explained by Z. marina shallow extent at both spatial scales, and also by rugosity when examining site-averaged patterns. Overlap of the two species along a transect was poorly predicted by physical context, but site-averaged range overlap was greater where depth profiles were more linear. Bottom profile complexity was the most consistently important predictor studied, confirming the importance of the geomorphic template on the zonation of these species. Furthermore, these findings suggest a greater sensitivity of Z. marina shallow extent to physical factors, and a greater sensitivity of Z. japonica deep extent to biotic factors.