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USGS1986

Interannual variability in biochemistry of partially mixed estuaries: Dissolved silicate cycles in northern San Francisco Bay

Much of the interannual variability in partially mixed estuaries in dissolved inorganic nutrient and dissolved oxygen patterns results from an enhancement or reduction of their annual cycle (generally via climatic forcing). In northern San Francisco Bay estuary the annual cycle of dissolved silicate supply peaks in spring and the effect of phytoplankton removal peaks in fall. Because riverine silicate sources are enhanced in wet years and reduced in dry years, the annual silicate cycle is modified accordingly. Effects of phytoplankton removal are reduced and delayed in wet years and enhanced and advanced (seen earlier) in dry years. Similar reasoning can apply to interpreting and understanding other mechanisms and rates.

Book chapter↗

USGS1978

Numerical simulation of dissolved silica in the San Fancisco Bay

A two-dimensional (vertical) steady-state numerical model that simulates water circulation and dissolved-silica distributions is applied to northern San Francisco Bay. The model (1) describes the strong influence of river inflow on estuarine circulation and, in turn, on the biologically modulated silica concentration, and (2) shows how rates of silica uptake relate to silica supply and mixing rates in modifying a conservative behavior. Longitudinal silica distributions influenced by biological uptake (assuming both vertically uniform and vertically decreasing uptake situations) show that uptake rates of 1 to 10 μg-at. l −1 day −1 are sufficient to depress silica concentrations at river inflows of 100–400 m 3 s −1 , respectively, and that the higher rates appear ineffective at inflows above 400 m 3 s −1 . The simulations further indicate that higher silica utilization in the null zone is not essential to depress silica concentrations strongly there. Advective water-replacement times at river inflows of 400, 200 and 100 m 3 s −1 are computed to be less than 25, 45 and 75 days, respectively, for a 120-km estuary-river system.

California↗