How does rising atmospheric CO2 affect marine organisms?

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Volume 2 Number 19:  1 October 1999

Give Peace a Chance by Giving Plants a Chance: Perusing our local newspaper of 26 September 1999, our attention was captured by the title of an opinion piece in the Perspective section: "To cultivate peace, we must first cultivate food."  Penned by former U.S. President Jimmy Carter, this article - albeit unknowingly, perhaps - makes an impressive case for the great good that can come from the ongoing rise in the air's CO2 content...

Journal Reviews
Forty Years of Cyclone Activity: Analyses of low pressure (cyclone) frequencies reveal no overall global changes from 1958 to 1997.

Changes in Cloud Cover: Cloud cover over three regions of the United States increased significantly from 1900 to 1987, while global air temperature rose by approximately 0.5C.  With an expected concomitant reduction in the diurnal temperature range, these regions have thus become less thermally stressful.

Making More and Brighter Clouds: Human-induced reductions in the surface tensions of cloud condensation nuclei were demonstrated to have the potential to significantly cool the planet by creating more numerous and more reflective cloud water droplets.

More CO2 = More Soil Organic Matter = More Crop Production: Atmospheric CO2 enrichment of wheat-soybean agroecosystems led to greater soil carbon sequestration and better soil structure.  The first of these effects slows the rate of rise of the air's CO2 content, while the second enhances plant productivity.

Effects of Elevated CO2 on a Tropical Canopy Tree Species: CO2-enriched branchlets of the tropical tree Luehea seemannii exhibited significantly greater rates of net photosynthesis than did branchlets grown at ambient CO2 concentrations even after 40 weeks of differential CO2 exposure.  Although elevated CO2 did not significantly affect current leaf growth or reproductive fitness, it did increase total nonstructural carbohydrate concentrations of terminal branchlets by 20%, suggesting that the first flush leaf growth in the coming year may be enhanced.

Effects of Elevated CO2 on an Alpine Grassland Ecosystem: Four years of atmospheric CO2 enrichment did not enhance the aboveground biomass of Trifolium alpinum, the only symbiotic nitrogen fixing species present in this study of a high Alpine grassland ecosystem, indicating that elevated CO2 does not necessarily confer a preferential growth advantage to nitrogen fixing species.  Thus, in such ecosystems, elevated CO2 would likely maintain biodiversity by not selectively favoring such species over non-nitrogen fixing species.

Seasonal Effects of Elevated CO2 on Snow Gum Seedlings: Snow gum seedlings grown at an atmospheric CO2 concentration of 700 ppm for eight months displayed significantly greater reductions in photosynthetic light utilization during cold winter months than did seedlings grown at ambient CO2.  However, in relatively warmer spring months, CO2-enriched seedlings overcame this low temperature-induced photoinhibition and exhibited photosynthetic rates and final biomass values that were 30 and 53% greater, respectively, than those of seedlings grown at ambient CO2.

Effects of Elevated CO2 and Environmental Stress on Soybean: Atmospheric CO2 enrichment increased total biomass in soybean, regardless of the presence of environmental stresses.  Although high temperature and low soil moisture reduced plant biomass, CO2-enriched soybeans still produced 24% more biomass than similarly stressed plants grown at ambient CO2.  In addition, elevated CO2 increased seed yield relative to control plants, regardless of environmental stresses.  In fact, the greatest stimulation in seed yield of 50% occurred in CO2-enriched plants that were simultaneously exposed to both high temperatures and low soil moisture contents.

Effects of Elevated CO2 and Ozone on Antioxidant Enzymes in Sugar Maple: Atmospheric CO2 enrichment and concomitant ozone exposure for six weeks increased and decreased the activities of various antioxidative enzymes in sugar maple seedlings, indicating that more research must be done to determine whether or not elevated CO2 will enhance or suppress oxidative stress in this species resulting from the uptake of ozone.