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Gaia and West Coast Marine Biosphere

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  • Mike Doran
    Warming Waters Identified as Cause of Marine Life Depletions off California November 7, 2003 CalCOFI data used to pinpoint mechanism underlying decline In the
    Message 1 of 1 , Nov 8, 2003
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      Warming Waters Identified as Cause of Marine Life Depletions off
      California

      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-
      plummeted.

      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-
      year deterioration.

      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
      the years."

      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
      separation.

      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






      Comments:

      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
      growth.

      During a warm period of the Eocine, there is evidence of large scale
      dieoff in the oceans . . .
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