FOR AN AT-RISK COASTAL ECOSYSTEM
Elkhorn Slough, located at the apex of the Monterey Bay Submarine Canyon, is California's second largest remaining coastal wetland (appx. 11 x 3 km). During the last glacial maximum, a river channel was incised through the Elkhorn Valley. Subsequent sea level rise invaded the incised valley creating Elkhorn Slough as the on-land extension of the Monterey Bay Canyon. A tidal embayment, salinity levels in the Slough may fluctuate seasonally from as high as 37 ppt in the drier summer months to as low as 17 ppt during the winter rainy season (Broenkow, 1977). Historically, the construction of dikes to impound tidal waters has diverted water flow and contributed to erosion of the main channel and surrounding wetlands. The home to many species of fish and invertebrates, Elkhorn Slough is also on the west coast bird migratory path: it has the second longest list (greater than 275 species) known in the United States. The wetlands provide important nursery and breeding grounds for many animals, and are regarded as one of the most important and productive ecological habitats in California. Its waters form part of the Monterey Bay National Marine Sanctuary, and many of its marshes form the boundaries of the Elkhorn Slough National Estuarine Research Reserve (ESNERR). Many agricultural lands lie outside the ESNERR boundaries, and current farming practices create runoffs of sediments, pesticides and fertilizers, which are infiltrating the Slough and creating additional risks for this ecosystem.
We are analyzing AVIRIS imagery to search for patterns of stress in vegetation, and obtaining data with higher spatial resolution and new spectral information of estuarine and aquatic plants with a hand-held spectroradiometer. We are taking readings along transects with known gradients of point and non-point source pollutants, and gradients with naturally occurring background stress. Although hyperspectral methods have been used in terrestrial systems for years, there have been few applications in coastal and shallow marine systems. Even less attention has been given to non-angiosperms and microorganisms that dominate intertidal floras. We are creating a spectral library for this ecosystem and systematically evaluating different stress indices for use with its estuarine plants. We are also evaluating chemical inputs to the system such as pesticides and nutrients. We will produce maps of vegetation distributions and stress that will provide management with a tool for sustainable ecosystem planning.
Click here for the web version of a poster pertaining to this work presented at the Sixth International Conference on Remote Sensing for Marine and Coastal Environments.
This portion of the project is also sponsored by the Cooperative Institute for Coastal and Estuarine Environmental Technology (CICEET), adminstered by NOAA and the University of New Hampshire.
