Giacomini Wetland Restoration Project: Restoration: What's the Long-Term Future of the Restored Wetlands?: Changes in Estuarine Salinity with Sea Level Rise

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What may have a greater effect on estuaries than changes in pH are changes in salinity with sea level rise and potential changes in freshwater inflow. As noted earlier, changes in salinity can change not only the type of wetland (salt vs. brackish vs. fresh), but the assemblage of species. Where this becomes particularly important is for those rare and perhaps even listed plant and wildlife species that rely on a specific water regime for persistence.

For example, Giacomini Wetlands supports several listed species that rely on specific water regimes for persistence. The federally threatened California red-legged frog (Rana aurora draytonii) is not an estuarine species, however, it often occurs in freshwater pockets along the edges of estuaries. Some studies have shown that eggs of red-legged frog are unlikely to persist in salinities higher than 4.5 ppt, and that larvae and adults are typically not found in areas where salinities exceed 7 ppt (Jennings and Hayes 1989). (As a point of comparison, ocean salinity in northern California is estimated at 34 ppt.) Another species, tidewater goby (Eucyclogobius newberryi), a federally endangered fish resident in estuaries, is considered a brackish species that prefers salinities around 10 ppt, but can persist in waters where salinities reach 25 ppt or higher (Swift 2003). While not observed in recent times, the federally endangered California freshwater shrimp (Syncaris pacifica) does occur in the Lagunitas Creek watershed, and, as its name implies, is reliant on having freshwater or very low salinity conditions.

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Some updated hydrodynamic modeling recently conducted by KHE for the Giacomini Wetlands suggested that sea level rise rates between 1 and 3 feet would have major implications for salinity regimes within the newly restored wetlands—and, by association, for the species that live or visit there. Average salinity increase—represented by the 50% or median salinity concentration)—increased 5.8 psu (102%) and 3.2 psu (409%) in upstream portions of the Giacomini Wetlands at the Lagunitas Creek-Bear Valley Creek confluence and Green Bridge locations, respectively (KHE 2009). Based on modeling, not only would habitats migrate upland, but changes in salinity structure with sea level rise could potentilly compress the amount of habitat available for organisms such as red-legged frog and tidewater goby. Figure 2 (322 KB PDF) shows a snapshot of salinity conditions along a longitudinal gradient in the Giacomini Wetlands with 1 foot of sea level rise. While salinities would obviously continue to vary seasonally, this graphic suggests that available habitat for red-legged frog and tidewater goby would migrate relative to existing available habitat and potentially shrink in size. However, this represents a conservative estimate of available habitat over a larger geographic scale and does not take into account seasonal variation in salinity or smaller "pockets" of available habitat that may persist that cannot be captured at this scale.

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What's the Long-Term Future of the Restored Wetlands?
Page 1. Introduction
Page 2. Sea Level Rise
Page 3. Precipitation, Run-Off, and Sedimentation
Page 4. Coastal Winds and Temperature
Page 5. Coastal Fog
Page 6. Coastal Upwelling
Page 7. Acidification of Coastal Waters
Page 8. Changes in Estuarine Salinity with Sea Level Rise
Page 9. Nitrogen Deposition
Page 10. Carbon Sequestration and Interactions of Carbon with Marsh Vegetation Communities
Page 11. Conclusions and References

 

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restoration includes:

Restoration Water, Water, and More Water How Long Will It Take For Tidal Wetlands To Develop? Two Years Later: Already Dramatic Improvements in Water Quality Giacomini Wetlands: A Haven for Ducks

Spring is in the Air--and in the Water Untangling the Food Web: Changes in Prey Base Following Restoration What's the Long-Term Future of the Restored Wetlands? How Can We Learn About the Restoration? How Can We Be A Part of the Restoration Process? Kids in Wetlands - Learning Through Experience Where Can We View the Restored Wetlands?

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