How does rising atmospheric CO2 affect marine organisms?

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How Earth's Coral Reefs Respond to Atmospheric CO2 Enrichment
Hughes, T.P., Baird, A.H., Dinsdale, E.A., Moltschaniwskyj, N.A., Pratchett, M.S., Tanner, J.E. and Willis, B.L. 2012. Assembly rules of reef corals are flexible along a steep climatic gradient. Current Biology 22: 736-741.

The authors write that "contemporary research on how climate change affects coral reefs has matured beyond the simplistic 'canary in the coal mine' concept to a more nuanced recognition that climate-related pressures such as bleaching (due to the loss of symbiotic zooxanthellae) and ocean acidification do not affect all species equally." And "in this context," as they continue, they indicate that "a critical issue for the future status of reefs will be their ability to maintain functional capacity in the face of the changes in species composition that are already underway due to multiple anthropogenic impacts."

What was done
To explore this subject in more detail, Hughes et al. applied a "rigorous quantitative approach to examine large-scale spatial variation in the species composition and abundance of corals on mid-shelf reefs along the length of Australia's Great Barrier Reef, a biogeographic region where species richness is high and relatively homogeneous." More specifically, they say they used "a hierarchical, nested sampling design to quantify scale-dependent patterns of coral abundances [for] five regions of the Great Barrier Reef [that they] sampled from north to south, each 250-500 km apart." Altogether, they thus identified and measured a total of 35,428 coral colonies on 33 reefs, categorizing each colony they encountered (including the majority of species that are too rare to analyze individually) into "ecologically relevant groups depending on their physiology, morphology and life history."

What was learned
The seven scientists report that the diverse pool of species they examined along the latitudinal gradient of the Great Barrier Reef "can assemble in markedly different configurations across a wide range of contemporary environments." With respect to temperature, for example, they indicate that "the geographic ranges of 93% of the 416 coral species found on the Great Barrier Reef extend northwards toward the equator (e.g., to Papua New Guinea, the Solomon Islands, and/or the Indonesian archipelago)," while "46% are also found in colder conditions further to the south." As for ocean acidification, they state that "globally, ocean surface pH has decreased by 0.1 unit since 1750 due to the uptake of atmospheric CO2, with a smaller 0.06 decline recorded for the tropics," citing Kleypas et al. (2006). In contrast, however, they report that contemporary variation in pH among various reef habitats on the Great Barrier Reef, as well as differences among short-term replicate measurements, span a range of 0.39 unit, from 8.37 to 7.98, citing Gagliano et al. (2010). And they rightfully note that this short-term and habitat-scale variability literally swamps that of latitudinal trends.

What it means
In light of their illuminating real-world observations, Hughes et al. say that their results "all point to a surprisingly resilient response by some elements of coral assemblages to spatial and temporal shifts in climatic conditions." And, therefore, they contend that "the flexibility in community composition that we document along latitudinal environmental gradients indicates that climate change is likely to result in a re-assortment of coral reef taxa rather than wholesale loss of entire reef ecosystems." And this demonstrable state of marine life affairs pretty much deflates the catastrophic prognostications typically put forth by the world's climate alarmists, who see nothing but death and destruction arising from CO2-induced ocean warming and acidification.

Gagliano, M., McCormick, M., Moore, J. and Depczynski, M. 2010. The basics of acidification: baseline variability of pH on Australian coral reefs. Marine Biology 157: 1849-1856.

Kleypas, J., Feeley, R.A., Fabry, V.J., Langdon, C., Sabine, C.L. and Robbins, L.L. 2006. Impacts of Ocean Acidification on Coral Reefs and Other Marine Calcifiers: A Guide for Future Research. Report of a workshop held April 18-20, 2005, St. Petersburg, Florida, USA, sponsored by NSF, NOAA and the U.S. Geological Survey.

Reviewed 17 October 2012