Benthic foraminiferal biodiversity response to a changing Arctic palaeoclimate in the last 24.000 years.

Abstract

Four sediment cores recovered from 1000 to 2500 m water depth in the Arctic Ocean, tracing the inflowing Atlantic water from Fram Strait, Yermak Plateau, northern Barents Sea continental slope as far as the Laptev Sea, have been analyzed for species richness and diversity. Samples were wet sieved after freeze-drying using a 63-µm sieve. Where possible at least 300 specimens were counted from the size fraction >63 µm, however, samples from deglacial periods are often affected by carbonate dissolution. In such samples foraminiferal numbers are low. Samples containing less than 40 specimens were excluded from statistical analyses. Because we are aware that specimen numbers <100 specimen are still critical for H analyses, core sections containing less than 100 specimens are highlighted in the figures. Here, we will characterize biodiversity trends by the two most widely used biodiversity measurements, the information function H (Buzas and Gibson, 1969) with its decomposition equation ln(S) and ln(E) (Buzas and Hayek, 1996), and the Fisher Alpha Index (Fisher, Corbett, and Williams, 1943). For spectral analysis the Fisher alpha record of core PS2837-5 was resampled at equally spaced 100-year intervals. For the spectral analysis, two methodes were used within the ANALYSERIES software package (Paillard et al., 1996): 1. The Blackman-Tuckey (1958) for its high confidence of the results; 2. The maximum entropy method (e.g. Haykin, 1983) for its high resolution. The cores reveal well-correlated biodiversity maxima and minima. Distinct periodicities of species richness variability of 1.57 kyr and 0.76 kyr characterize the Late Weichselian, and of 1.16 kyr and 0.54 kyr even more pronounced the Holocene. The biodiversity maxima/minima coincide with terrestrial and marine warm and cool events at high northern latitude. We suggest that either the physiology of most rare species is temperature sensitive, or sustained food supply increased the taxonomic richness during warmer intervals.