How does rising atmospheric CO2 affect marine organisms?

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Rawson Lake, Northwestern Ontario, Canada
Laird, K.R. and Cumming, B.F. 2009. Diatom-inferred lake level from near-shore cores in a drainage lake from the Experimental Lakes Area, northwestern Ontario, Canada. Journal of Paleolimnology 42: 65-80.

The authors developed a history of changes in the level of Lake 259 (Rawson Lake, 4940'N, 9344'W) within the Experimental Lakes Area of northwestern Ontario, Canada, based on a suite of near-shore gravity cores they analyzed for diatom species identity and concentration, as well as organic matter content. This work revealed "a distinct decline in lake level of ~2.5 to 3.0 m from ~800 to 1130 AD." This interval, in their words, "corresponds to an epic drought recorded in many regions of North America from ~800 to 1400 AD," which they say "is often referred to as the Medieval Climatic Anomaly or the Medieval Warm Period." They also note that the Canadian prairies are currently "experiencing reductions in surface-water availability due to climate warming and human withdrawals" and that "many regions in the western U.S. have experienced water supply deficits in reservoir storage with the recent multi-year drought," but they say that "these severe multi-year drought conditions pale in comparison [our italics] to the many widespread megadroughts [our italics] that persisted for decades and sometimes centuries [our italics] in many parts of North America over the last millennium." Thus, the close association between the severity and duration of drought and warmth within the affected region of North America suggests that the degree of warmth during the Medieval Warm Period in the Experimental Lakes Area of Canada was likely much greater than the degree of warmth so far experienced there during the Current Warm Period.