Biology Reference
In-Depth Information
A HOME BY MANY NAMES
Scientists classify the species found in San Francisco Bay based on where
they live.
•
Marine
organisms live in salty ocean water.
•
Estuarine
or
euryhaline
species prefer a salt water and fresh water mix.
•
Native
species are of local origin.
•
Non-native, exotic
, and
introduced
species hail from elsewhere but were
brought to the bay by humans.
•
Pelagic
species such as Northern Anchovy inhabit open water.
•
Demersal
organisms are found on or near the bottom.
•
Structure-associated
organisms favor piers, rocks, and pilings.
•
Benthic
species live in the bottom mud or sand.
•
Resident
species live in the bay year-round.
•
Anadromous
fish live in the ocean as adults but return to the estuary and
travel upstream through rivers and creeks to reproduce.
where: the material on the bay floor, currents, water temperature, and tur-
bidity. Warmer waters, for example, put off sharks but please halibut. Tur-
bidity—the murkiness of a given patch of water—affects the amount of
light that can penetrate the water column. Turbidity from suspended sedi-
ments limits the types of plants and plankton that can grow and the amount
of food available for fish; turbidity can also result from algal blooms
.
The ocean exerts a powerful influence on local biodiversity. Positioned
midway down the California coastline, the bay is a place where two distinct
groups of coastal marine fauna overlap. One group is associated with
warm, tropical waters that typically reach as far north as Point Conception,
near Santa Barbara. The other is found in cooler waters, which generally
extend from the Central Coast north to Canada. The mixing point of these
zones can occur anywhere in between, including opposite the Golden
Gate. When the ocean switches from cold to warm during one of its decadal
regime changes, tropical species arrive in the bay within a few months.
Between 1998 and 1999, the Pacific Ocean underwent a regime change
called the North Pacific Gyre Oscillation that sent cooler waters into the
bay (see p. 45, “Weather and Ocean Cycles”). This shift also turned the
bay's species communities upside down. At that time, biologists were
shocked by a plankton bloom occurring in the bay as late as October. No
one had seen such a phenomenon for decades. State Department of Fish
and Game surveys showed the abundance of bottom-dwellers suddenly
leap of the charts. Huge numbers of juvenile crab and English Sole mi-
grated into the bay, while shrimp, Plainfin Midshipmen, and Sand Dab
also prospered (see Figure 5). As larvae, all of these species rely on phyto-
