UC Marine Council

Elkhorn Slough, a National Estuarine Research Reserve, is one of the most important estuarine systems in California. Despite the protection status of Elkhorn Slough, agriculture in its watershed has increased dramatically since 1970. Associated with this agriculture is an increase in sedimentation, which deposits in creek bottoms, marshes, mudflats, and channels. This sedimentation may alter wetland structural features, which are a major component of habitat for rare species, and drive patterns of plant and animal community assemblages. This research addresses the questions: Has the structure of salt marsh wetlands within Elkhorn Slough changed since 1970? If yes, can these changes be linked to increased agriculture? Are there differences in wetland changes between sub-catchments of the watershed? The following wetland features will be examined: plant community type and distribution, width of tidal channels, length of channels, and sinuosity of the channel network. If the research identifies changes to these features, effort will be made to link them to changes in upland features indicative of increased sediment through multiple regression analysis. Remote sensing technologies will be used to quantify historic modifications to the Elkhorn Slough watershed and wetlands. Landsat Multispectral Scanner (MSS) and Thematic Mapper (TM) imagery will be analyzed to quantify the extent of land use change from 1973 to 2000, through the process of land use classification and a post-classification change analysis. Color and color infra-red aerial photos will be used in conjunction with Geographic Information Systems (GIS) to measure changes in wetland structural features over this same time period. This research will assess the extent of habitat degradation in tidal channels, which serve as a nursery for juvenile fish in Elkhorn Slough and Monterey Bay. The research will also provide information about wetland conditions prior to intensive agriculture, and the extent to which changes have occurred, which the Natural Resources Conservation Service and the Elkhorn Slough Foundation will use to guide decisions related to wetland restoration and management.