How does rising atmospheric CO2 affect marine organisms?

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Victoria Land Coast, Antarctica
Hall, B.L., Hoelzel, A.R., Baroni, C., Denton, G.H., Le Boeuf, B.J., Overturf, B. and Topf, A.L. 2006. Holocene elephant seal distribution implies warmer-than-present climate in the Ross Sea. Proceedings of the National Academy of Sciences USA 103: 10,213-10,217.

The authors collected skin and hair - and even some whole-body mummified remains - from raised-beach excavations at various locations along Antarctica's Victoria Land Coast (~7730'S, 16330'E) that they identified by both visual inspection and DNA analysis as coming from southern elephant seals (Mirounga leonina) and which they analyzed for age by means of radiocarbon dating. Results from fourteen different locations - which they describe as being "well south" of the seals' current "core sub-Antarctic breeding and molting grounds" - indicate that what they call the Seal Optimum began about 600 BC and ended about AD1400, "broadly contemporaneous with the onset of Little Ice Age climatic conditions in the Northern Hemisphere and with glacier advance near [Victoria Land's] Terra Nova Bay." These findings, in their words, indicate "warmer-than-present climate conditions" over a period of time that encompassed both the Medieval and Roman Warm Periods, as well as the intervening Dark Ages Cold Period, and that "if, as proposed in the literature, the [Ross] ice shelf survived this period, it would have been exposed to environments substantially [our italics] warmer than present."