Biology Reference
In-Depth Information
Suisun Bay's quiet shallows. (Francis Parchaso)
deposition of tons of sediment swept downstream during the gold-min-
ing era.
Between San Pablo Bay and Suisun Bay—the fourth sub-bay—the flow
of water up and down the bay must squeeze through the half-mile-wide
Carquinez Strait. The dictionary defines a
strait
as “a narrow passage be-
tween two seas,” though in this case the passage links two bays. Suisun is
deeper than San Pablo, and lies at the mouth of the official confluence of
the Sacramento and San Joaquin rivers. It's ringed on the north shore by
golden hills, windmills, and the region's largest brackish marsh, and on the
south shore it's encircled by oil refineries, industry, and small towns. The
strait and Suisun Bay are the primary mixing zone of fresh river and salty
ocean waters.
In hydrological terms, the Suisun, San Pablo, and Central bays all join
together in a larger single system that is a classic estuary, with rivers flow-
ing out to sea and tides coming in and out; the South Bay, however, has
become an estuarine backwater.
Bay waters are in constant motion. The most massive of these water move-
ments are caused by ocean tides. Ocean water pours into the bay and
pushes upstream during
flood tides
. The surge subsides again, pulling
water out of the bay, on
ebb tides
.
Tides are caused by the gravitational pull of the sun and moon on the
ocean. Two high tides and two low tides occur each day. The largest tide, a
spring tide
, occurs at the full and new moons year-round, not only in
spring. At these times, the moon, sun, and earth align so that each rein-
