How does rising atmospheric CO2 affect marine organisms?

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A 5000-Year History of Ocean and Climate Conditions Along Vancouver Island, British Columbia, Canada
Reference
Hay, M.B., Dallimore, A., Thomson, R.E., Calvert, S.E. and Pienitz, R. 2007. Siliceous microfossil record of late Holocene oceanography and climate along the west coast of Vancouver Island, British Columbia (Canada). Quaternary Research 67: 33-49.

What was done
The authors analyzed the vertical distributions of diatoms, silicoflagellates and biogenic silica found in two sediment cores recovered from the inner and outer basins (4904'N, 12509'W and 4902'N, 12509'W, respectively) of Effingham Inlet, British Columbia, Canada, describing the climatic implications of what they found.

What was learned
Hay et al. report that "a period of warmer and drier climate conditions and possibly increased coastal upwelling offshore occurred ca. 1450-1050 calendar years before present," i.e., from about AD 550-950. In addition, noting that "the patterns observed in the diatom record of Effingham Inlet are consistent with regional marine and terrestrial paleoenvironmental records," they go on to report that "coast range glaciers ... showed a hiatus from 1500 to 1100 calendar years before present," and that this "period of more productive conditions ... was correlative with increased regional primary and marine fish production." Also, their data indicated that concentrations of Skeletonema costatum, which they say "is limited by low temperatures," were much greater over the AD 550-950 period (which appears to represent the Medieval Warm Period in this part of the world) than in any portion of the following (most recent) millennium.

What it means
The authors' data, as well as the data of others they cite, indicate the presence of the Medieval Warm Period in both marine and terrestrial settings throughout the general region where they worked, which period appears to have been significantly warmer than the centuries that preceded and followed it. Hence, Hay et al.'s work presents yet another example of the widespread occurrence of the Medieval Warm Period and its superiority to the Current Warm Period in terms of maximum temperatures, i.e., peak temperatures during the Medieval Warm Period in this part of the world were warmer than those of the Current Warm Period.

Reviewed 1 August 2007