MICROFOSSIL EVIDENCE FOR RECENT CHANGES TO HUDSON BAY AREA OCEANOGRAPHY: LINKAGES BETWEEN SUB-ARCTIC FLUVIAL DISCHARGE AND THE OCEANIC RESPONSE

A combined geochemical and micropaleontological (foraminifera, planktic tintinnids) dataset has been generated from box cores (BC’s) collected from the Hudson Bay (HB) into the Hudson Strait. The downcore microfaunal changes are calibrated to the geochemical data where present to act as proxies for chemical parameters in cores where there are no chemical measurements. These will also provide evidence for changes to the lateral extent of freshwater plumes extending into the Hudson Bay from peripheral fluvial systems in recent times. After generating a U-series geochronology (²¹⁰Pb) it is evident that all the box cores contain an increase in brackish water proxies and a decrease in total calcareous foraminifera (e.g., Bulimina sp., Fursenkoina sp.) in younger parts of the core that is coincident with increased abundances of agglutinated foraminifera (e.g., Reophax spp., Trochammina spp.) (BC3 - NE HB; BC10 - central HB; BC12 - NW HB; and BC15 - Hudson Strait). These microfossil trends are correlated to higher organic matter in the cores, likely from regional regulated fluvial systems (i.e., Churchill River, Great Whale River), which is interpreted as causing a lowered pH in the benthic sediments and pore water – conditions less favourable for the preservation of calcareous tests. However, an increased riverine influence is more favourable for tintinnid populations, which thrive on suspended particulate organic matter and more euhaline waters. These results illustrate how fluvial systems have significant potential to change the physical oceanography in this sub-arctic oceanic ecosystem. As a corollary, any anthropogenic alteration to natural sub-arctic fluvial systems will have a concomitant influence on the Hudson Bay area oceanography.