How does rising atmospheric CO2 affect marine organisms?

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Lily Pond, General Creek Watershed, Sierra Nevada Mountains, California, USA
Beaty, R.M. and Taylor, A.H. 2009. A 14,000-year sedimentary charcoal record of fire from the northern Sierra Nevada, Lake Tahoe Basin, California, USA. The Holocene 19: 347-358.

Based on high-resolution charcoal analysis of a 5.5-m-long sediment core extracted from Lily Pond (393'26"N, 1207'21"W) in the General Creek Watershed on the west shore of Lake Tahoe in the northern Sierra Nevada in California (USA), as well as a 20-cm-long surface core that "preserved the sediment-water interface," the authors developed a 14,000-year record of fire frequency. This work revealed, in their words, that "fire episode frequency was low during the Lateglacial period but increased through the middle Holocene to a maximum frequency around 6500 cal. yr BP" that "corresponded with the Holocene temperature maximum (7000-4000 cal. yr BP)." Thereafter, as the temperature gradually declined, so too did fire frequency decline, except for a multi-century aberration the researchers describe as "a similar peak in fire episode frequency [that] occurred between c. 1000 and 600 cal. yr BP during the 'Medieval Warm Period'," which they say was followed by an interval "between c. 500 and 200 cal. yr BP with few charcoal peaks [that] corresponded with the so-called 'Little Ice Age'." Last of all, they found that the "current fire episode frequency on the west shore of Lake Tahoe is at one of its lowest points in at least the last 14,000 years." With respect to the future, Beaty and Taylor thus conclude that "given the strong relationship between climate and fire episode frequency, warming due to increased levels of greenhouse gases in the atmosphere may increase fire episode frequency to levels experienced during the 'Medieval Warm Period'." And since the part of the planet they studied is currently experiencing one of the lowest levels of fire frequency of the last 14,000 years, it is clear that it is currently nowhere near as warm there now as it was during the Medieval Warm Period.