How does rising atmospheric CO2 affect marine organisms?

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Volume 2 Number 24:  15 December 1999

Scientist-Gods and Journalist-Prophets: In Modern-Day Climatology, the Boundaries Blur: We ruminate on the use and non-use of caveats in popular and scientific writing about the potential for CO2-induced climatic change and its possible consequences.

Journal Reviews
The Global Deep Water Roller Coaster Ride: Does It Shepherd Earth's Climate Back and Forth Between Medieval Warm Period and Little Ice Age Conditions?: An analysis of several tracers of water movement in the world's oceans suggests that deep water formation in the Southern Ocean may have significantly slowed over the past several decades.  The study describes how this phenomenon may be related to the global warming of the past century.

Deep Convection Helps Tropics Keep Their (Relative) Cool: In a first principle-driven analysis of data obtained from the Tropical Ocean Global Atmosphere - Coupled Ocean-Atmosphere Response Experiment, the authors demonstrate that deep moist convection over the tropical oceans operates in a thermostat-like fashion to keep sea surface temperatures there from rising much above 30C.

Still Melting After All These Years: Analyses of sediment cores collected from the Weddell Sea suggest that the East and West Antarctic ice sheets are still in the midst of contracting from their maximum glacial extensions, and that it will yet be a very long time before they reach their normal interglacial minimum sizes.  Hence, their continued shrinking is normal and unrelated to the modest global warming of the past century or so.  Furthermore, there is nothing man can do to stop it.

Methane Hydrates and Global Sea Level: An analysis of potential sea level fall due to submerged methane hydrate melting and subhydrate gas release suggests that the decline could be on the order of the sea level rise that might occur from the thermal expansion of the oceans, melting of nonpolar ice, and the melting of the West Antarctic ice sheet in response to massive global warming.

History of the Last Interglacial: A reconstruction of climate variability during the last interglacial indicates that the onset of instability that led to the last great ice age occurred about 10,800 years after the beginning of the full interglacial, which is essentially the exact same point in time, relative to the current interglacial, in which we now sit.  Ought we not thus be just a little bit worried about global cooling?

Effects of Elevated CO2 and Osmotic Stress in Arabidopsis thaliana: Arabidopsis thaliana plants grown in elevated CO2 exhibited decreased stomatal conductance and increased rates of photosynthesis.  Thus, atmospheric CO2 enrichment increased plant water-use efficiency for this species.  In addition, the presence of an osmotic stress or the addition of abscisic acid amplified this CO2 response, resulting in even greater plant water-use efficiencies relative to those observed in plants exposed to ambient CO2 concentrations.

Effects of Competition and Nitrogen on Mixed-Species Responses to Elevated CO2: After 60 days of atmospheric CO2 enrichment, legumes tended to exhibit greater CO2-induced growth responses than grasses across a large soil nitrogen gradient.  When grown as isolated plants, individual growth responses to elevated CO2 could not be scaled-up to accurately represent species growth responses in a mixed-species competitive community.  However, the CO2-induced growth responses of species raised in monocultures were indicative of species responses in the community setting, suggesting that plant-plant interactions (regardless of the identity of the neighboring plants) need to be incorporated when studying community responses to elevated CO2.

Effects of Elevated CO2 on Grassland Community Structure: Nutrient-poor calcareous grasslands of Switzerland did not exhibit any significant biomass responses to atmospheric CO2 enrichment until the end of the second year of CO2 fumigation, at which time biomass was found to be 20% greater in CO2-enriched plots relative to ambiently-grown controls.  From this point on, biomass production continued to increase, and the CO2-induced enhancement of this growth parameter rose to 21 and 29% after three and four years of atmospheric CO2 enrichment, respectively.  In addition, after three years, CO2 enriched plots exhibited a marginally significant increase in biodiversity relative to plots exposed to ambient CO2 concentration, indicating that the rising CO2 content of the air can increase ecosystem biodiversity even when soil nutrients may be limiting plant growth.

Effects of Elevated CO2 and O3 on Photosynthesis in European Beech Trees: European beech seedlings grown at an atmospheric CO2 concentration of 660 ppm for an entire year were insensitive to elevated O3 concentrations, while seedlings grown at 367 ppm CO2 displayed significant O3-induced reductions in photosynthesis.  Thus, elevated CO2 completely ameliorated the negative impacts of O3 on photosynthesis in this valuable woody species.

Predicting the Growth Response of Woody Plants to Elevated CO2: Eight woody species of different life form and habit all exhibited significant increases in plant dry weight in response to two months of atmospheric CO2 enrichment, with deciduous species being more responsive than evergreen species.  As a predictive indicator, the authors showed that the specific leaf area of woody plants grown in ambient CO2 concentration was positively correlated with observed CO2-induced increases in relative growth rates.