Surface sediment samples from the Hudson Bay system were analysed in order to examine the role of key regulators of arctic marine productivity - light and nutrients as affected by freshwater stratification and sea-ice cover - on the spatial distribution and production of dinoflagellate cysts. Total cyst fluxes vary from 0.2×106 to 30.6×106 cysts m-2 a-1, with the highest values observed in eastern Hudson Bay. A total of 24 cyst taxa, representing 11 genera of five orders, were identified and distribution maps of the most common taxa have been produced. This is the first record of Echinidinium aculeatum, Echinidinium karaense, cf. Echinidinium delicatum, Islandinium brevispinosum, Selenopemphix quanta, cysts of Protoperidinium americanum, cysts of cf. Biecheleria sp. and Polarella glacialis in the Hudson Bay system. Dinoflagellate cyst assemblages show distinct spatial patterns revealing three compositional domains: eastern Hudson Bay, western-central Hudson Bay and Hudson Strait. The eastern domain is characterised by a dominance of autotrophic cysts of Pentapharsodinium dalei whereas the western-central domain is characterised by autotrophic Operculodinium centrocarpum with some contribution by heterotrophic Polykrikos sp. var. arctic morphotype and Polykrikos spp. Sites from Hudson Strait are distinguished by an overwhelming prevalence of heterotrophic Protoperidiniaceae cysts, mainly Islandinium minutum, and have the highest values of sedimentary biogenic silica, used as a proxy for diatom productivity. Sediment geochemical tracers are used as proxies for freshwater inputs (lignin and its biomarkers) and nitrate availability (nitrogen isotopes), and sea-ice concentrations derived from passive microwave data as a proxy for light availability. Sea-ice regulated length of the dark season has a negligible influence on the proportion and production of heterotrophic (dark-adapted) versus autotrophic (light-dependent) dinoflagellate cysts, perhaps due to the location of our study area on the southern fringe of the Arctic. Instead, cyst populations in Hudson Bay are primarily regulated by vertical stratification and nitrate availability, while in Hudson Strait the pivotal mechanism constitutes food availability. 2013 Elsevier B.V.
Bibliographical noteFunding Information:
This paper is dedicated to our friend and colleague, Dr. Klaus Hochheim, who tragically lost his life while doing sea ice research in the Canadian Arctic, September of 2013. We are grateful to the officers and crew of CCGS Amundsen for the support during the cruise, M. O'Brien for the assistance with coring, and Z. Sandwith and A. Price for the help with sample preparation. Funding and support were received from ArcticNet , a Canadian Network of Centres of Excellence, Fisheries and Oceans Canada (G.S. & R.M.), the Academy of Finland (grant 252512 to M.H.), Natural Sciences and Engineering Research Council of Canada (V.P.) , Canada Foundation for Innovation (CFI) , Canada Research Chairs (CRC) , Canada Excellence Research Chairs (CERC) Program and University of Manitoba (G.S.). Journal editors Richard Jordan and Frans Jorissen, as well as Jens Matthießen and an anonymous reviewer offered comments that significantly improved the manuscript.
- Biogenic silica
- Dinoflagellate cysts
- Hudson Bay