How does rising atmospheric CO2 affect marine organisms?

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Raffles Sų, Liverpool Land, East Greenland
Cremer, H., Wagner, B., Melles, M. and Hubberten, H.-W. 2001. The postglacial environmental development of Raffles So, East Greenland: Inferences from a 10,000-year diatom record. Journal of Paleolimnology 26: 67-87.

Working with a sediment core extracted in September 1994 from the deepest part of Raffles So (an island) on Raffles O (a lake) located at 70°35.7'N, 21°32.1'W in the outer Scoresby Sund region of East Greenland, the authors analyzed a number of core geochemical properties and the types and amounts of diatom flora found within the core. In doing so, they determined that "more or less ice-free conditions during summer may have prevailed during the early Holocene until ca. 1800 yrs BP," after which colder conditions led to "a perennial lake-ice cover" that favored the growth of Fragilaria capucina varieties, which at times accounted for close to 100% of the core's planktonic diatoms. During a 400-year period centered on about 1100 yrs BP, however, Cyclotella species accounted for as much as 27% of the planktonic diatoms, indicative of "decreased lake-ice cover in summer," which significant abundance was never replicated again throughout the upper portion of the core, with subsequent Cyclotella species numbers accounting for less than 10% of the total assemblage and sometimes only 1 or 2%. Therefore, we conclude that the peak warmth of the MWP was greater than that of the CWP.