How does rising atmospheric CO2 affect marine organisms?

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Volume 2 Number 12:  15 June 1999

Is It Science or Politics?: As controversy swirls about the subject of carbon dioxide and climate change, as powerful forces converge to hammer out international accords on how to deal with what may or may not be the environmental dilemma of our day, and as reputations are created and destroyed in the rough-and-tumble world of ....  Wait a minute.  Are we talking science or politics here? Perhaps this is the environmental dilemma of our day: we have lost all track of what exactly it is we are engaged in.  Is it the search for truth?  Or is it a game of smoke and mirrors designed to obfuscate a hidden social agenda?

Journal Reviews
Nearly Half a Million Years of Climate and CO2: A study of climatic and atmospheric change over the past 420,000 years, as reconstructed from the longest ice core ever recovered from anywhere on the planet, reveals that (1) over four complete glacial-interglacial cycles, earth orbital changes elicit changes in temperature, which then cause atmospheric CO2 concentration to either rise or fall, (2) the four preceding interglacials were all significantly warmer than the current one, even though there was no more CO2 in the air then than there has been during the current interglacial, (3) even during these much warmer interglacials, the West Antarctic ice sheet did not collapse, and (4) the current interglacial is, by far, the longest of all those in the 420,000 record, suggesting we are probably long overdue for another ice age.  All four of these observations argue strongly against the primary premises of the Kyoto protocol.

Miocene Climate and CO2: A temperature history of the period 9 to 25 million years ago, which was reconstructed from sediment cores obtained from three deep sea drilling sites, reveals the existence of several CO2-climate relationships that appear to be "in conflict with greenhouse theories of climate change."

Global Warming and Shifts in British Bird Ranges: A 20-year study of the breeding distributions of British birds reveals that over a two-decade period of global warming, the birds have extended their northern range limits by approximately 19 km while making little change in their southern boundaries.  This response parallels that observed in European butterflies and what would be expected for plants in the face of concomitant increases in both air temperature and atmospheric CO2 concentration.

Global Warming and Shifts in European Butterfly Ranges: A study of the range distributions of European butterflies reveals that over the past century of global warming, most species have extended the northern boundaries of their ranges while holding their southern boundaries constant.  This response parallels that observed in British birds and what would be expected for plants in the face of concomitant increases in both air temperature and atmospheric CO2 concentration.

Global Warming and Shifts in Bird Breeding Dates: A 29-year study of the breeding habits of the Mexican jay in the Chiricahua Mountains of Arizona reveals that this particular species of bird was building nests 10.8 days earlier in 1998 than it was in 1971 and laying eggs 10.1 days earlier.  The authors indicate that these changes were associated with significant trends in increased monthly minimum temperatures over the same time period.  The positive shifts in bird behavior may be related to both the temperature increase and the ongoing rise in the air's CO2 content.

Responses of a "Living Fossil" (Ginkgo biloba) to Elevated CO2: Saplings of Ginkgo biloba grown in greenhouses with an atmospheric CO2 concentration of 560 ppm displayed significant reductions in stomatal density and index compared to plants grown at 350 ppm CO2.  In addition, these reduced stomatal parameters were similar to those measured on fossilized leaves dating back to the Triassic and Jurassic, suggesting that Ginkgo's ancient relatives were very efficient in their water-use during those periods of historically CO2-enriched atmospheres.

Effects of Elevated CO2 on Spring Wheat: Spring wheat grown in FACE plots with 550 ppm CO2 exhibited a 28% increase in net photosynthesis that persisted throughout the growing season, thereby indicating that photosynthetic acclimation did not occur.  In addition, CO2-enriched plants displayed rates of stomatal conductance that were 36% lower than control plants grown at 370 ppm CO2.  Thus, atmospheric CO2 enrichment enhanced plant water-use efficiency by about 33% on a whole crop basis.

Photosynthetic Acclimation to Elevated CO2 in Pine: Pinus radiata grown in New Zealand for four years in open-top chambers with an atmospheric CO2 concentration of 650 ppm displayed enhanced rates of photosynthesis that varied with needle age.  Current-year needles displayed a 65% photosynthetic enhancement and no sign of photosynthetic acclimation, whereas one-year old needles exhibited significant reductions in rubisco activity and content.  However, this acclimation was not complete; and after four years of continual CO2 enrichment, one-year old needles still had photosynthetic rates that were 31% greater than rates measured in similar needles on trees grown at 360 ppm CO2.

Effects of Elevated CO2 and Defoliation on Maple and Aspen: Atmospheric CO2 enrichment of 70-days increased total plant dry weight in 1-year old and 2-year old saplings of maple and aspen, respectively, by approximately 10% under optimal growth conditions.  When stressed by simulated herbivory, which removed 50% of their leaf area, slower growing CO2-enriched maple trees displayed a 28% increase in dry weight compared to defoliated controls, while the faster growing CO2-enriched aspen exhibited an 11% increase in dry weight relative to their ambiently-grown counterparts.  In addition, elevated CO2 induced photosynthetic down regulation in non-defoliated maple, but not aspen saplings.  However, upon defoliation, CO2-enriched maple saplings upregulated photosynthesis and displayed photosynthetic rates that were nearly three-fold greater than those observed in defoliated controls.

Effects of Nutrient and Genotype on CO2 Response of Leucadendron Species: Four different Leucadendron plants grown in open-top chambers for one year at an atmospheric CO2 concentration of 700 ppm, displayed significantly higher rates of photosynthesis and leaf starch concentrations than plants grown at 350 ppm, regardless of genotype and soil fertility.  Thus, the rising CO2 content of the air should maintain genetic diversity in these species.