How does rising atmospheric CO2 affect marine organisms?

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Volume 2 Number 5:  1 March 1999

Caution and Credibility in the Debate Over Global Change: A Strange Mix of Science and Politics: In the 12 February 1999 issue of Science, S.I. Rasool, former NASA Chief Scientist for Global Change (1987-1991), makes a plea for "scientific responsibility in global climate change research."  Noting that several major findings in this area over the past few years have ultimately "been retracted or shown to be erroneous," he suggests that scientists "must be careful not to rush to publish," stating that "the price for a wrong decision based on spurious analyses may not be insignificant.  We have much sympathy for Rasool's feelings on this important matter...

Journal Reviews
Causes of Coral Bleaching: A review of the scientific literature weakens the oft-cited claim that global warming is responsible for recent coral bleaching events, while it strengthens the likelihood of a solar radiation connection.

A Review on Coral Bleaching: A review of the literature suggests sea temperature (both warm and cold anomalies) and solar irradiance are the leading causes of large-scale coral reef bleaching events.

Coral Bleaching from Environmental Stresses: This review of the literature lists a number of environmental stresses that may induce coral bleaching either separately or in concert with one another. The mechanisms responsible for the actual bleaching, however, remain poorly understood.

Reefs Happen: An introductory article to a special issue on coral reefs indicates that corals are proficient at adapting to environmental change but vulnerable to the direct effects of the growing human population.

Zooxanthellae Diversity and Coral Bleaching: A long-term study reveals large seasonal fluctuations in coral zooxanthellae density that may indicate that frequent coral bleaching is a natural phenomenon.

Water Relations of Oak Trees at Elevated CO2: Italian oaks growing near naturally high CO2 springs (500 to 1000 ppm CO2) exhibited decreased rates of leaf conductance and transpiration during summer droughts relative to control trees growing at ambient CO2 concentration.  Trees near high CO2 springs also responded to drought conditions by reducing their foliage area to decrease water loss by transpiration.

Effects of Elevated CO2 in Dry Loess Grassland Species: Four perennial C3 species, common to dry loess grasslands near Budapest and grown in open-top chambers, exhibited increased rates of net photosynthesis and varying rates of transpiration in response to 231 days of atmospheric CO2 enrichment.  All species studied exhibited significant increases in water-use efficiency, indicating that the increasing CO2 content of the air will enable them to better deal with the dry hot summers characteristic of this region.

Interactive Effects of Water Stress and CO2 on Alfalfa: Alfalfa plants grown in open-top chambers at 600 ppm CO2 displayed better overall water status than plants grown at 340 ppm CO2 after the imposition of water stress.  Plants in elevated CO2 achieved this physiological advantage by producing greater amounts of nonstructural carbohydrates, which ultimately reduced transpiration, and by altering thylakoid membrane lipid composition, which preserved membrane integrity and functionality.

Effects of Elevated CO2 and Water Stress on Brassica juncea: Well-watered Brassica juncea plants grown in CO2-enriched open-top chambers for one season exhibited greater net photosynthetic rates and root, stem, and leaf dry masses than plants grown in ambient CO2.  With the onset of water-stress, the percentage increase in dry mass and yield were even greater than they were for well-watered CO2-enriched plants, thereby indicating that the growth-promoting effects of atmospheric CO2 enrichment will not be thwarted by inadequate soil moisture levels in this species.

Interactive Effects of Elevated CO2, Mycorrhization and Drought on Oak Trees: Young oak seedlings grown at an atmospheric CO2 concentration of 1100 ppm for 10 to 15 weeks exhibited significant increases in total biomass regardless of mycorrhizal root colonization or soil water status.