Species distribution and depth habitat of recent planktic foraminifera in Fram Strait, Arctic Ocean

Abstract

To describe the horizontal and vertical distribution of recent planktic foraminifera in Fram Strait (Arctic), plankton samples were collected in the early summer of 2011 using a MultiNet sampler (>63 µm) at 10 stations along a west–east transect at 78°50′N. Five depth intervals were sampled from the sea surface down to 500 m. Additionally, sediment surface samples from the same locations were analysed. The ratio between absolute abundances of planktic foraminifera in the open ocean, at the ice margin and in the ice-covered ocean was found to be approximately 2:4:1. The assemblage was dominated by the polar Neogloboquadrina pachyderma (sin.) and the subpolar Turborotalita quinqueloba, which accounted for 76 and 15% of all tests in the warm, saline Atlantic waters and 90 and 5% in the cold and fresh Polar waters, respectively. Both species had maximum absolute abundances between 0 and 100 m water depth, however, they apparently lived shallower under the ice cover than under ice-free conditions. This indicates that the depth habitat of planktic foraminifera in the study area is predominantly controlled by food availability and not by temperature. The distribution pattern obtained by plankton tows was clearly reflected on the sediment surface and we conclude that the assemblage on the sediment surface can be used as an indicator for modern planktic foraminiferal fauna.

Keywords

• Planktic foraminifera
• Fram Strait
• Arctic Ocean
• depth habitat
• N. pachyderma (sin.)
• T. quinqueloba