Gaia and West Coast Marine Biosphere
- View SourceWarming Waters Identified as Cause of Marine Life Depletions off
November 7, 2003
CalCOFI data used to pinpoint mechanism underlying decline
In the mid-1970s, the abundance of marine life along the western
coast of the United States began a momentous decline, the start of a
trend that today has yet to rebound. Numbers of fish, seabirds, kelp
beds, and zooplankton-the critical base of the oceanic food web-
A recent study led by a scientist at Scripps Institution of
Oceanography at the University of California, San Diego, has found
warming ocean temperatures as the likely driving force behind the 25-
Scripps's John McGowan and his colleagues used data recorded by the
California Cooperative Oceanic Fisheries Investigations (CalCOFI) to
examine the mechanism behind the changes seen in the California
Current, the large current originating in the northern Pacific Ocean
that passes along the western coast of North America.
"We had seen a big change in the California Current ecosystems since
the late 1970s, and in this report we looked at the possible
mechanisms accounting for that change. We found that the most likely
cause is a change in the upper-ocean heat content," said McGowan, who
published the results in Deep Sea Research Part II, in a special
edition that focused on the California Current and CalCOFI. The paper
was coauthored by Steven Bograd and Ronald Lynn of the National
Marine Fisheries Service and Arthur Miller of Scripps.
The authors caution that similar forces impacting ecosystem
populations could emerge elsewhere, especially if ocean temperatures
continue to rise. They say their results demonstrate that significant
changes in sea-temperature balances can "greatly alter the marine
community ecosystem structure and productivity, sounding the alarm to
the potential impacts of a global warming trend." They further note
that the ability to distinguish between human-caused and climate-
caused changes will be necessary in the future in order to model
marine population trends for conservation and management decisions.
In coming to their conclusion, McGowan and his coauthors looked at
two other possible causes for the ecosystem decline, testing and
ultimately showing that those are not likely. McGowan also shows that
fishing pressure cannot be blamed solely for the decline. "The
massive declines we've seen in fish eggs and larvae population after
1976 cannot be due entirely to fishing pressure because many of the
larvae are from species that are simply not harvested, and they too
have decreased," said McGowan.
Rather, the paper places the spotlight squarely on a "regime shift"
to warmer upper-ocean temperatures. This led to a disturbance in the
method in which lower, nutrient-rich water mixes with the upper
ocean. Essentially, a thickening of the warmer water layer caused the
nutrient-rich waters to deepen, disrupting the food supply for
plankton and other sea life in the upper layers.
"After this regime shift we saw the massive changes take place, not
just in plankton but in fish, seabirds, kelp beds, and nearshore
invertebrates," said McGowan. "In the larger sense this paper
confirms and reaffirms the notion that there are large-scale
environmental changes happening on land, lakes, and in our ocean.
It's uncertain how long it's going to continue and whether it will
increase in velocity or decrease. It's fear of the unknown, but
something big is happening. I think an awful lot has to do with
global warming and that's going to continue."
The conclusions reached in the paper are one example of the value and
importance of the CalCOFI program, launched more than 50 years ago to
explore the dynamic California Current. Although initially focused on
the disappearance of the sardine off the California coast, the data
collected by the CalCOFI program-from recordings
such as ocean circulation, temperature, oxygen levels, and salinity
to observations of marine life-have become invaluable.
"There are a lot of principles of interactions that can be derived
from this magnificent 50-year data set," said McGowan. "It's been
called a 'national treasure' because it's so highly interdisciplinary
and so accurate, so trustworthy."
Says Bograd: "CalCOFI is the world's longest-running
multidisciplinary field program. The accumulation of physical,
chemical, and biological data spanning more than five decades now
allows us to explore the dynamics of the California Current and its
ecosystems across a range of temporal scales. CalCOFI also has been
instrumental in training numerous students and young scientists over
McGowan believes the value of CalCOFI will increase in the years
ahead as science and government continue to pursue questions of human-
produced versus naturally produced changes. He says that since its
beginning, the CalCOFI program has focused on distinguishing this
The value of CalCOFI surfaced as far back as the 1950s, when a 1958-
59 El Nino event was identified as having a profound effect on marine
populations. That event was, as McGowan puts it, an "eye-opener" for
future El Nino events.
Volume 50 of Deep Sea Research Part II, published this fall, was
devoted to CalCOFI and the California Current. Fourteen research
papers in the issue highlight various aspects of the California
Current, including "CalCOFI: a half century of physical, chemical,
and biological research in the California Current System" by Bograd
and his colleagues and "Long-term change and stability in the
California Current System: Lessons from CalCOFI and other long-term
data sets" by Ginger Rebstock.
"It seemed fitting to present a sample of research papers from
CalCOFI in a special volume, as a celebration of more than 50 years
of successful scientific endeavors," said Bograd. "Hopefully it will
also reinforce the notion that long-term sampling programs such as
CalCOFI are absolutely necessary if we are to understand how marine
ecosystems respond to climate change. As oceanographic sampling
programs go, CalCOFI is the crown jewel."
Scripps Institution of Oceanography
This material is more conductive than lifeless, diffused water. It
is part of the trend that has resulted in the 1,400 year drought in
the four corners and the fires in the SW. Much of it is hydrology
driven, and the rest from CO2 NOT as a green house gas but as an
ELECTRICAL forcing, both in terms of gas exchange increasing
conductivities overall (and making for more difficulty in the
biosphere creating contextually a signal in cloud modulations) but
also in terms of acidities and erosion rates, and rates of plant
During a warm period of the Eocine, there is evidence of large scale
dieoff in the oceans . . .