231Pa/230Th ratios in sediments as a proxy for past changes in Southern Ocean productivity
Article Abstract:
Two isotopes, 231 protactinium (231Pa) and 230 thorium (230Th), can be used to estimate fluctuations in the productivity of the Southern Ocean during glacial and interglacial periods. These isotopes are useful because how much of them is deposited in ocean sediments depends on the activity of marine plankton, which in turn depends on atmospheric carbon dioxide levels. Ratios of 231Pa and 230Th show that productivity in the Atlantic south of the Antarctic polar front (APF) was lower during glacial periods than during interglacials but that the converse was true north of the APF.
Publication Name: Nature
Subject: Zoology and wildlife conservation
ISSN: 0028-0836
Year: 1993
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Evidence from nitrogen isotope ratios for enhanced productivity during formation of eastern Mediterranean sapropels
Article Abstract:
The sapropels or organically abundant sediments that were deposited in the eastern Mediterranean during the Holocene and Upper Pleistocene were probably produced by increased levels of planktonic activity that in turn derived from the Nile's increased runoff. Nitrogen isotope ratios from sedimentary cores supported the hypothesis that higher primary productivity generated the sediment over the alternative supposition that the sediments resulted from the improved preservation of carbon in anoxic bottom waters.
Publication Name: Nature
Subject: Zoology and wildlife conservation
ISSN: 0028-0836
Year: 1992
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Glacial-interglacial changes in nutrient utilization in the equatorial Pacific Ocean
Article Abstract:
The decreased nutrient utilization in the sediments of eastern equatorial Pacific Ocean (EEP) during the Last Glacial Maximum (LGM) was due to greater supply of nitrate to the water surface as compared to its consumption by phytoplanktons. Although biological activity increased during the LGM, it was not comparable with the nitrate supply. EEP did not function as a CO2 sink as the nutrient content of the water during this time was high.
Publication Name: Nature
Subject: Zoology and wildlife conservation
ISSN: 0028-0836
Year: 1995
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