Editors' Choice Highlights of the recent literatureOceans

Reading Planktonic History

+ See all authors and affiliations

Science  28 Jul 2000:
Vol. 289, Issue 5479, pp. 509
DOI: 10.1126/science.289.5479.509c

Many reconstructions of sea surface temperatures are based on foraminiferal “transfer functions,” which combine counts of the relative numbers of different kinds of forams found in marine sediments with knowledge of the environmental conditions in which those species live now, in order to estimate water temperatures in earlier times. In the high-latitude Norwegian-Greenland Sea, modern carbonate sediments are dominated by a single polar-adapted planktonic foraminifer, Neogloboquadrina pachyderma sinistral. Plankton-based paleotemperature reconstructions for this area depend on the abundance of this foram, whose presence or absence is interpreted as indicating warm or cold conditions, respectively. However, if the ecological preferences of this foram were different in the past than they are now, then its utility as a paleoenvironmental proxy would be compromised.

Huber et al. have measured how the shell size of this foraminifer has varied over the past 1.3 million years in six sediment cores from the Norwegian-Greenland Sea. They find that the maximum diameter has increased over that interval, and interpret this as evidence of adaptation to cold water environments. This would mean, among other things, that the carbonate-poor intervals before 1.1 million years ago do not necessarily indicate severe glacial conditions, and that sea surface temperature reconstructions using transfer functions for periods older than that may be inaccurate. — HJS

Palaeogeogr. Palaeoclimatol Palaeoecol. 160, 193 (2000).

Navigate This Article