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Science Support for Wetland Restoration in the Napa-Sonoma Salt Ponds, San Francisco Bay Estuary
Miles, A. K., Fregien, S., Takekawa, J. Y, Martinelli, G. M., Schoellhamer, D. H., Duffy, W. G., Schlosser, J. P., Saiki, M. K.
Napa-Sonoma marshes

The San Francisco Bay estuary has experienced tremendous human population growth during the past 150 years and a subsequent loss of natural habitats and degradation of water quality. More than 91% of the tidal wetlands (also referred to as intertidal wetlands in the estuarine zone) has been lost to reclamation for farmland, salt evaporation ponds, and residential or industrial property (Josselyn 1983, Nichols et al. 1986, Goals Project 1999). Many native species dependent on tidal wetlands are now endangered or candidate species for listing.

In recent attempts to reverse the decline of tidal wetland species, several conservation groups have supported conversion of salt ponds and other bayland areas to tidal wetlands in the estuary. Projections for wetland restoration from the multi-agency San Francisco Estuary Baylands Ecosystem Goals report (Goals Project 1999) suggest that only a few hundred hectares of the more than ten thousand hectares of salt ponds in the estuary will likely remain through the next century. However, artificial salt evaporation pond systems have become an integral habitat component for wildlife in the estuary during the past century (Ver Planck 1958). The salt ponds currently support large and diverse communities of migratory birds. For example, the Napa Marshes in the North Bay were designated as a "Globally Important Bird Area" by the American Bird Conservancy because a large proportion of the shorebirds and waterfowl in the entire estuary are found in the salt pond habitats of that region (Anderson 1970, Accurso 1992, G. Page, unpubl. data).

Only a few descriptive studies (Carpelan 1957, Anderson 1970, Lonzarich and Smith 1997) have examined ecological processes in these salt systems including their value for wildlife. Hypersaline systems such as salt ponds typically support simple macroalgal, macroinvertebrate, or fish assemblages, but the physical and biological processes affecting these assemblages may be quite complex (e.g. Caumette et al. 1994; Rodriquez-Valera et al. 1985, Pinkney and Pearl 1997). Ecological interactions and physical processes in these artificial salt ponds are poorly understood (see Lonzarich and Smith 1997), but the importance of lower trophic organisms and their use by migratory waterbirds has been identified in similar systems (Herbst and Bradley 1993, Herbst and Castenholz 1995, Elphick and Rubega 1995).

Therefore, the goal of this research project was to examine the ecological and hydrological function of the Napa-Sonoma salt ponds and their importance for waterbirds, including integrated studies on primary productivity, macroinvertebrates, plants, and fishes. We compared nutrient concentrations, algal primary productivity, and zooplankton community composition in salt ponds of varying salinity; and, we determined their importance as year-around habitats for forage fishes and as nurseries for larval or juvenile life stages, including fishes of recreational and commercial importance. In addition, we examined radio-marked black-necked stilts (Himantopus mexicanus) in order to determine their distribution, movements, and habitat use. This progress report presents the preliminary research results from the first year of the fieldwork.

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