How does rising atmospheric CO2 affect marine organisms?

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Volume 2 Number 7:  1 April 1999

The Future of Forests: Trees, it seems, are growing much more profusely now than they did one and two centuries ago; yet some people want to turn back the clock and recreate the biological paucity of the past.  Do they not know progress when they see it?

Journal Reviews
Sea Surface Temperatures and Coral Bleaching: A 30-year history of sea surface temperatures in the northeastern Caribbean Sea suggest that bleaching events there are triggered by sharp changes in temperature.

Coral Bleaching Follows Rapid Warming: A large coral bleaching event was observed in a portion of Australia's Great Barrier Reef following a rapid increase in sea water temperatures.

Coral Bleaching Follows Rapid Cooling: A coral bleaching episode associated with rapid water cooling was documented in a nearshore reef in the southern Caribbean ocean, leading the authors to suggest that the key to coral bleaching episodes may be the rapidity of temperature change rather than its direction of change (warming or cooling).

Heat-Shock Proteins and Coral Bleaching: Samples of coral experiencing high temperature stress produced a heat-shock protein that is also induced by high levels of UV radiation.  In discussing this finding, the authors describe how heat-shock proteins increase the abilities of corals to withstand high temperatures.

Oxidative Stress and Coral Bleaching: Oxidative stress in the Agaricia tenuifolia coral, due to either elevated temperatures or UV radiation, can be ameliorated by either the induction of antioxidant enzymes or coral bleaching itself.

Effects of Elevated CO2 on Silver Birch: Four-year-old silver birch seedlings grown in CO2-enriched open-top chambers located south of Edinburgh, England, had 43% more leaves, nearly 60% more biomass, and a total annual net carbon budget that was 110% larger than that displayed by trees grown in ambient CO2.

Effects of Elevated CO2 on Root Growth and Respiration in Scots Pine: Three-year-old Scots pine seedlings grown in CO2-enriched open-top chambers for six months produced significantly greater total root length (122%) and dry mass (135%) than seedlings grown in ambient CO2.  In addition, roots of CO2-enriched seedlings contained 90% more starch than control seedlings and had significantly higher nitrogen concentrations.

Effects of Elevated CO2 and Temperature on Growth of Five Boreal Trees: Faster growing deciduous tree seedlings displayed larger initial CO2-induced dry mass increases than slower growing coniferous trees.  However, CO2-induced enhancements of relative growth rates steadily dropped for the deciduous seedlings, while they steadily rose for conifers over the three-month study, indicating that slower growing species may also exhibit positive responses to the increasing CO2 content of the air.

Effects of Elevated CO2 and Soil Nitrogen on Growth of Aspen: Cuttings of four quaking aspen genotypes that were grown in open-top chambers for five months with elevated CO2 displayed increased rates of net photosynthesis compared to control cuttings grown in ambient CO2, regardless of soil nitrogen availability or genotype.  In the presence of high soil nitrogen, elevated CO2 significantly increased fine root length and root turnover, thereby transferring greater amounts of carbon to the rhizosphere.

Responses of Beech and Spruce Trees to Elevated CO2 and Soil Quality: Eight genotypes of beech and spruce saplings grown in open-top chambers for two years exhibited increased rates of photosynthesis throughout the study, regardless of soil type or nitrogen content.  Although down regulation was observed in both species, regardless of genotype, rates of photosynthesis were still greater than those observed in plants grown at ambient CO2 concentration.  In addition, all genotypes of both species tended to exhibit reduced rates of stomatal conductance, and consequently, increased water-use efficiencies.  These several observations indicate that genetic biodiversity within beech and spruce populations will be maintained as the CO2 content of the air continues to rise.