referred to as the null zone and has been shown to support a 
significant phytoplankton-zooplankton food web. On the other 
hand, the "South Bay", the portion stretching from the indus¬ 
trial city of South San Francisco to the Silicon Valley of San 
Jose, has little freshwater inflow and functions more like a 
large lagoon. Occasional freshwater cells may move into the 
basin from the North Bay during the winter. In the summer, the 
major freshwater source is treated domestic effluent. 
The Urbanized Estuary 
Flying into San Francisco or viewing the region from space, 
one is impressed with the urban development surrounding the Bay. 
Certainly, the land-use along the edge of the Bay has undergone 
a significant change over the past 170 years; these changes un¬ 
doubtedly have had an influence on the physical, chemical, and 
biological functioning of the estuary. Nichols et al. (1986) 
have written an excellent summary of the changes that have oc¬ 
curred in San Francisco Bay since 1850 and I want to briefly 
summarized their remarks. 
One of the major activities was the diking of "swamp and 
overflowed lands" and subsequent draining of the wetlands for 
agricultural purposes. The greatest loss occurred in the Delta, 
where the entire wetland system was lost due to the construction 
of levees. Small portions of the wetland system can be observed 
today as islets within the river channels and along levee banks. 
However, the increasing trend towards placing a rip-rap on le¬ 
vees and removing vegetation is eliminating even these small 
riparian areas. The tidal salt marshes of the Bay have faired 
only slightly better, with over 85 percent having been diked or 
filled for agricultural, salt, ponds, or urbanization. The 
largest remaining wetland system in the estuary is located 
around Suisun Bay. These wetlands are also diked; however, 
water flow is managed to support habitat to attract waterfowl 
for hunting by the over 150 private duck clubs in the region. 
At the time that wetlands were being diked, another anthro¬ 
pogenic process was imperceptibly building more shallow water 
habitat. To retrieve gold from the foothills, miners used large 
water monitors to wash the overburden and gold-containing sedi¬ 
ment through sluiceways and into rivers, the Delta and, after 
several decades, the Bay. Hydraulic mining was halted in 1884, 
but the redistribution of sediment from rivers to the Bay went 
on for the following half century. In several locations in 
Suisun and San Pablo Bays, new marshlands were created by the 
sediment, and many former deep harbors were silted in. 
The gold of California transplanted many Easterners to the 
Bay region, who brought with them the cultural and culinary 
tastes of their Atlantic upbringing. With the completion of the 
transcontinental railroad, the means to transport entire 
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