Effects of watershed and estuarine characteristics on the abundance of submerged aquatic vegetation in Chesapeake Bay subestuaries |
| |
Authors: | Xuyong Li Donald E Weller Charles L Gallegos Thomas E Jordan Hae-Cheol Kim |
| |
Institution: | (1) Virginia Institute of Marine Science, School of Marine Science, College of William and Mary, Gloucester Point, VA 23062, USA |
| |
Abstract: | Watershed land use can affect submerged aquatic vegetation (SAV) by elevating nutrient and sediment loading to estuaries.
We analyzed the effects of watershed use and estuarine characteristics on the spatial variation of SAV abundance among 101
shallow subestuaries of Chesapeake Bay during 1984–2003. Areas of these subestuaries range from 0.1 to 101 km2, and their associated local watershed areas range from 6 to 1664 km2. Watershed land cover ranges from 6% to 81% forest, 1% to 64% cropland, 2% to 38% grassland, and 0.3% to 89% developed land.
Landscape analyses were applied to develop a number of subestuary metrics (such as subestuary area, mouth width, elongation
ratio, fractal dimension of shoreline, and the ratio of local watershed area to subestuary area) and watershed metrics (such
as watershed area). Using mapped data from aerial SAV surveys, we calculated SAV coverage for each subestuary in each year
during 1984–2003 as a proportion of potential SAV habitat (the area < 2 m deep). The variation in SAV abundance among subestuaries
was strongly linked with subestuary and watershed characteristics. A regression tree model indicated that 60% of the variance
in SAV abundance could be explained by subestuary fractal dimension, mean tidal range, local watershed dominant land cover,
watershed to subestuary area ratio, and mean wave height. Similar explanatory powers were found in wet and dry years, but
different independent variables were used. Repeated measures ANOVA with multiple-mean comparison showed that SAV abundance
declined with the dominant watershed land cover in the order: forested, mixed-undisturbed, or mixed-developed > mixed-agricultural
> agricultural > developed. Change-point analyses indicated strong threshold responses of SAV abundance to point source total
nitrogen and phosphorus inputs, the ratio of local watershed area to subestuary area, and septic system density in the local
watershed. |
| |
Keywords: | |
本文献已被 SpringerLink 等数据库收录! |
|