Marine Biomarkers

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Science  27 Oct 2000:
Vol. 290, Issue 5492, pp. 673
DOI: 10.1126/science.290.5492.673d

Knowledge of the concentration of 14C in the surface ocean is important for understanding ocean ventilation rates, deep water formation, variations in atmospheric 14C inventories, abrupt climate changes, and changes in oceanic circulation. Measurements of sea-surface 14C are typically made on the calcium carbonate found in planktonic foraminifera, corals, or bivalve shells. In some areas of the ocean, however, calcium carbonate is either not preserved or not produced, which makes it necessary to find other suitable phases for determining sea surface 14C concentrations. One possible source of material is the organic fraction of marine sediments. However, the carbon contained in these sediments is isotopically heterogeneous due to the multiplicity of its origins.

Now Pearson et al. have avoided this complication by analyzing a group of biomolecules from a single class of compounds. They identified eight sterols that accurately record the amount of 14C in surface waters at the time of their synthesis. These marine biomarkers could make it possible to determine 14C inventories of problem areas like the Southern Ocean, and to avoid vital effects and depth-dependent effects that sometimes interfere with the use of foraminiferal calcite. — HJS

Paleoceanography15, 541 (2000).

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