Biology Reference
In-Depth Information
A scientist samples a square meter of the estuary for invasive plants. White plas-
tic quadrats provide measuring tools for diverse organisms and bay conditions.
Some of the longest standing records of bay conditions reside with the U.S. Geo-
logical Survey, which set up the very first tide gauge at the Golden Gate more than
100 years ago. (Francis Parchaso)
every two to seven years, and every few decades the whole North Pacific
experiences a change so profound that entirely different types of fish take
up residence in the bay.
“The bay is not a static thing,” says aquatic ecologist Jim Cloern of the
U.S. Geological Survey. Cloern had been studying the bay for over 20 years
when he saw plankton growing in places and at times they had never been
seen before. His state colleagues surveying fish began pulling in more sole
than halibut and seeing unusual surges in bottom-dwellers. “In terms of
these biological communities, it's almost like the bay flipped from one
state to another state. Ecologists call these 'regime shifts' or 'crossing a
threshold,' ” he says.
To survive in such a changeable place, local fish and wildlife must be
unusually resilient—able to endure winter floods and summer droughts,
as well as times of scarce food between times of plenty. Lately, however,
more than a few species have been having a tough time adapting to the
most dramatic changes of all: the arrival of people. During the past 150
years, entrepreneurs and engineers have straightened rivers, culverted
creeks, drained marshes, and paved coastlines. They have also rerouted the
flow of water from land to sea, directing the lion's share into reservoirs,
faucets, and irrigation pipes.
“We have plumbed more of our system and diverted more of our fresh
