Benthic foraminifera in an Arctic fjord : recent distribution and fauna of the last two millennia

Abstract

The main objective of the PhD study was to improve the knowledge about the ecology of the benthic foraminiferal faunas thus increasing the precision of benthic foraminifera as indicators for modern and past Arctic fjord and shelf environments. The investigation of living (stained) benthic foraminifera assemblages in Kongsfjorden (western Svalbard) was performed on inter-annual and seasonal time scale. The fauna was subsequently compared to the environmental conditions including e.g. hydrology, primary productivity as well as the sediment structure, oxygen profiling, pore-water chemistry, in order to identify the driving forces leading to faunal variations. The newly gained knowledge on benthic foraminifera ecology was applied to interpret paleoceanographic changes the past 2000 years recorded in the two marine sediment cores from the Kongsfjorden and Hinlopen Troughs (northern Svalbard). The results show that living benthic foraminiferal faunas in Kongsfjorden are mainly controlled by the food supply from pelagic production which is closely related to the timing and amount of Atlantic Water (AW) inflow in addition to the release of suspended matter from the surrounding glaciers. The strongest response to the high seasonal productivity and related summer intrusions of AW is shown by dominant Nonionellina labradorica. Further, the study shows that benthic foraminifera inhabiting the micro-environments prefer to live in proximity to the bio-irrigation system (burrows, tubes), what allows them to use more extensively the oxygen and labile organic matter storage. The two paleorecords show a distinct faunal signal from AD 1200-1500 attributed to the development of highly productive oceanographic fronts between the Arctic and Atlantic water masses. This period is followed by more severe conditions from AD 1500-1900 corresponding to the Little Ice Age. The observed long term trends indicate the overall gradual reduction in glacial influence and a possible oceanographic warming of the NW Svalbard shelf over the last two millennia.