Biology Reference
In-Depth Information
Once through the Golden Gate and in the bay, the average parcel of
water can travel up to nine miles with the tides, touching the shore of the
South Bay in about two hours and reaching the banks of the state capital in
about eight hours. At the Golden Gate, a flood tide can raise the water
level by up to five and a half feet, which gradually diminishes to about
three feet upriver near Sacramento. In contrast, tides flowing into the
South Bay are amplified. With no major river inlets in this semienclosed
system, tides tend to slosh back and forth. Water can linger in these back-
waters for a month or more. The exchange happens more rapidly in the
vicinity of the Central Bay, where tides and currents may drive a ribbon of
seawater from the Gulf of the Farallones to the Bay Bridge and back in one
tidal cycle.
To seasoned bay captains, the tides feel as familiar underfoot as the
topography of dry land. Says Byron Richards, the retired captain of the
science research vessel
Polaris,
“When you're fighting the tide, it feels like
the boat's going uphill.”
San Francisco Bay exhibits much stronger, more pronounced, changes
in the spring/neap tidal cycle than do East Coast estuaries. A spring tide
can bring 30 percent more water into and out of the bay than a neap tide.
“All of the mixing and circulation of the water—including the transport of
anything in the water like sediments, salt, and organisms—changes dra-
matically over a 14-day cycle, with a pretty big ecosystem response,” says
The USGS research vessel
Polaris
was originally built for pleasure, not science.
When insurance tycoon and delta marshland developer Lee Allen Phillips built the
96-foot-long yacht in 1927, he named it
Pasada Mañana
(which translates from
Spanish as “maybe tomorrow”). Phillips took her into the ocean to troll for marlin
and swordfish, sailed her up to the delta to visit farmers on his properties, and
used her as a floating hotel to entertain the likes of Winston Churchill and Herbert
Hoover. During Prohibition, he even sailed her to Canada and brought back whiskey
in two copper tanks hidden behind a secret wall panel. (Francis Parchaso)
