Changes in Planktic Foraminiferal Distribution, Productivity, and Preservation in the Barents Sea During the Last Three Millennia

Abstract

Planktic foraminifers are ubiquitous marine calcifiers sensitive to ocean biogeochemical and physical changes. Their fossil remains have thus been widely used for the reconstruction of past oceanographic and climatic changes. Here, we have investigated the distribution patterns of planktic foraminiferal species, their abundance, shell size, and preservation state in two sediment cores from the northern and southern Barents Sea during the last three millennia and compared them with a living assemblage from the water column. The study area covers the cold Arctic zone in the north and the warm boreal zone in the south. In the north, we found very low to almost zero abundances of fossil planktic foraminifers, mainly since c. 1300 Common Era (C.E.), and dominance by the polar species Neogloboquadrina pachyderma. In the south, higher abundances were found, where the taxa was dominated by the subpolar species Turborotalita quinqueloba, Globigerinita uvula and Neogloboquadrina incompta. The highest foraminiferal concentrations occurred in the transition phases between cold and warm periods, with a rapid decrease in abundance during the last two hundred years coinciding with the Industrial Revolution. The lack of planktic foraminifers since c. 1300 C.E. in the north and the consistently low %CaCO₃ are attributed to CaCO₃ dissolution in the sediment, possibly driven by the decomposition of total organic matter as suggested by high %TOC, high surface productivity, and the presence of solely agglutinated benthic foraminifers. Dissolution of CaCO₃ muted the signals of paleoproductivity and paleoclimate in the north, while the southern site showed clear variability throughout the investigated time interval.