Reduction of Aedes dorsalis by enhancing tidal action in a northern California marsh

Full tidal action was restored to a 28-ha marshland in the brackish region of the San Francisco Bay Estuary to evaluate the impact of increased tidal circulation on Aedes dorsalis abundance. One year after project completion, mosquito abundance had decreased by 98.7%, from an average of 3.6 to 0.3 4th-instar larvae per dip. Larvicide applications have consequently been reduced from approximately 6 to zero per year. The effects on the marsh plant community and marsh elevation were assessed during the first 2.3 years since project completion. Total coverage by sedges, rushes, reeds, cattails, and brass buttons increased almost 80% at the expense of pickleweed (-65%) and peppergrass (-34%). Sedimentation on the marsh plain has averaged 1.2 cm/year, which is about 10 times greater than the average rate of sea level rise for the region. In general, the marsh ecosystem has begun to acquire characteristics that typify immature, highly productive, fully tidal brackish marshes of the region.