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 re gion of the San Francisco Bay Estuary to evaluate the impact of increa sed tidal circulation on Aedes dorsalis abundance. One year after proj ect completion, mosquito abundance had decreased by 98.7%, from an ave rage of 3.6 to 0.3 4th-instar larvae per dip. Larvicide applications h ave consequently been reduced from approximately 6 to zero per year. T he effects on the marsh plant community and marsh elevation were asses sed during the first 2.3 years since project completion. Total coverag e by sedges, rushes, reeds, cattails, and brass buttons increased almo st 80% at the expense of pickleweed (-65%) and peppergrass (-34%). Sed imentation 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 regi on. In general, the marsh ecosystem has begun to acquire characteristi cs that typify immature, highly productive, fully tidal brackish marsh es of the region.