Seminar: Thursday Feb. 7, 2008 3:30-4:30pm, Mueller Room 153
Speaker: Dr. James E. Cloern
Email: jecloern@usgs.gov
Title: Surprises from Long Term Ecological
Observations: Examples from
Abstract:
Ecological observations sustained over decades often
reveal abrupt changes in biological communities that
signal altered ecosystem states. We report a large shift in the biological
communities of
first detected as increasing phytoplankton
biomass and occurrences of new seasonal blooms that began in
1999. This
phytoplankton increase is paradoxical because it occurred in an era of
decreasing wastewater
nutrient inputs and reduced nitrogen and
phosphorus concentrations, contrary to the guiding paradigm
that algal biomass in estuaries increases in
proportion to nutrient inputs from their watersheds.
Coincidental changes included sharp declines in the
abundance of bivalve mollusks, the key
phytoplankton consumers in this estuary, and record
high abundances of several bivalve predators:
Bay shrimp, English sole, and Dungeness crab. The phytoplankton increase is consistent with
a trophic
cascade resulting from heightened predation on
bivalves and suppression of their filtration control on phytoplankton
growth. These community changes in
followed a state change in the
intensity, amplified primary production, and
strengthened southerly flows. These
diagnostic features
of the East Pacific ‘‘cold phase’’ lead to
strong recruitment and immigration of juvenile flatfish
and crustaceans into estuaries where they
feed and develop. This study, built from
three decades
of observation, reveals a previously
unrecognized mechanism of ocean–estuary connectivity.
Interdecadal oceanic regime changes can propagate
into estuaries, altering their community
structure and efficiency of transforming land-derived
nutrients into algal biomass.
James Cloern (jecloern@usgs.gov) is an aquatic ecologist
who began working for the USGS in 1976.
He has BS (1970) and MS (1973) degrees in zoology from
the
in zoology/limnology from
in lakes, streams, and estuaries, using
field measurements and numerical modeling to identify the patterns
and mechanisms of ecosystem
variability. He is leader of the USGS
team that collects water quality
measurements in
Dr. James E. Cloern is a
senior research scientist at the U.S. Geological
Survey in Menlo Park,
in limnology and ecosytem
modeling. For three decades he has led
team research focused on
natural processes of variability and human
disturbance.
http://sfbay.wr.usgs.gov/access/wqdata/overview/people/jim.html
Water Quality of