How does rising atmospheric CO2 affect marine organisms?

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How Elevated CO2 Affects Beetles Feeding on Their Favorite Foliage
Johns, C.V., Beaumont, L.J. and Hughes, L. 2003. Effects of elevated CO2 and temperature on development and consumption rates of Octotoma championi and O. scabripennis feeding on Lantana camara. Entomologia Experimentalis et Applicata 108: 169-178.

What was done
The authors performed, in their words, "a factorial experiment to examine the effects of elevated CO2 and increased temperature on both the leaf-chewing adults and leaf-mining larvae of two closely related beetle species, Octotoma championi Baly and Octotoma scabripennis Guerin-Meneville (Coleoptera: Chrysomelidae), feeding on the host plant Lantana camara L. (Verbenaceae)." The study was conducted in environment-controlled growth chambers maintained at atmospheric CO2 concentrations of 360 or 700 ppm and at low (22C/18C) or high (25C/21C) day/night temperatures, where well-watered and fertilized plants were grown from cuttings for just over 13 months.

What was learned
Johns et al. report that "under the high temperature treatment, plants grown at ambient CO2 suffered wilting and premature leaf loss, despite daily watering [our italics], but that "this effect was ameliorated at elevated CO2." They also report that "the wilting of plants in the ambient CO2/high temperature treatment reduced the emergence success of the beetles," and that "consumption rates of free-living beetles were not affected by either CO2 or temperature," whereas "in short-term trials using excised foliage, beetles given no choice between ambient and elevated CO2-grown foliage consumed more from ambient plants."

What it means
In the words of the authors, "this study indicates that under future conditions of higher temperatures, amelioration of water stress in host plants growing in elevated CO2 may benefit some endophagous insects by reducing premature leaf loss," and they note that "under some circumstances, this benefit may outweigh the deleterious effects of lower leaf nitrogen," which is typically described by climate alarmists as posing a major problem for insects in a high-CO2 world of the future. In addition, Johns et al. say their results indicate that "foliage consumption under elevated CO2 by mobile, adult insects on whole plants may not be significantly increased, as was previously indicated by short-term experiments using excised foliage," which latter finding has also been claimed by climate alarmists to be a major problem for insects (and the plants upon which they feed) in an elevated-CO2 atmosphere. Clearly, new experimental evidence, such as from this study, is proving their claims to be far from robust.

Reviewed 29 December 2004