Dr F Marret-Davies
Dr C Mahaffey
No more applications being accepted
Funded PhD Project (European/UK Students Only)
The Arctic Ocean is undergoing rapid environmental change. The Arctic is warming twice as fast as the global average. The areal extent of sea ice has declined by 9% per decade since 1978 (Comiso 2012). Expansion of ice free regions has increased Arctic primary productivity by 30% since 1998 (Arrigo and van Dijken 2015). These environmental changes have led to regional changes in phytoplankton community size structure and diversity, with large phytoplankton being replaced by smaller cells (e.g. Mousing et al., 2017). Increased dominance of phytoplankton such as dinoflagellates has implications for proliferation of toxic phytoplankton blooms (e.g., Richlen et al., 2016). While these changes have been detected recently in the upper water column (e.g., Onda et al., 2017; Crawford et al., 2018), the variability in phytoplankton biomass, diversity and emergence of species succession in the recent past is unknown. This project will use micro-paleontological and biogeochemical techniques to understand the variation in the plankton community over the past 200 years and the environmental drivers for this change.
Using sediment cores from the Barents Sea and Fram Strait in the Arctic Ocean recently collected as part of the NERC Changing Arctic Ocean programme (https://www.changing-arctic-ocean.ac.uk), this project will focus on using microfossils composition, with a specific focus on dinoflagellate cysts, to understand changes in the plankton community and reconstruct the Arctic environment. Dinoflagellates are a major contributor to primary production in the ocean but are also responsible for red ties and harmful algal blooms, which can be a threat to food webs (e.g., Natsuike et al., 2017). Dinoflagellates have a complex life cycle, which include for 20% of the species, a resting cyst that is preserved well in sediments (e.g., de Vernal and Marret, 2007). The distribution of dinocyst species is now very well known in the Northern Hemisphere due to decades of collaborative studies (e.g., Marret and Zonneveld, 2003); de Vernal et al., 2013). Furthermore, these palaeoceanographical proxies can be used to quantitatively reconstruct annual and seasonal sea-surface conditions (temperature, salinity, sea-ice cover duration and primary productivity) for recent geological time periods (late Quaternary) in the Arctic region (e.g., de Vernal et al., 2013; Cormier et al., 2016; Pienkowski et al., 2017; Allan et al., 2018; Limoges et al., 2018; Matthiessen et al., 2018).
The objectives of this project are to (a) analyze dinoflagellate cyst content in sediment cores collected in contrasting regions of the Arctic Ocean including the marginal ice zone, region influenced by the Atlantic inflow and deep Arctic ocean (b) use the modern analogue technique (Guiot and de Vernal, 2007) to quantitatively reconstruct sea-surface parameters using a modern database of ~1900 sites from the Northern Hemisphere and (c) use organic geochemical biomarkers (e.g. dinosterols) and dating techniques to reconstruct the composition and sedimentation rates of sediment cores (e.g. (Kohlbach et al., 2016; Tesi et al., 2017).
Full funding (fees, stipend, research support budget) is provided by the University of Liverpool. Formal training is offered through partnership between the Universities of Liverpool and Manchester in both subject specific and transferable skills to the entire PhD cohort and at each University through local Faculty training programmes.
Allan E, de Vernal A, Knudsen MF, et al. (2018) Late Holocene Sea Surface Instabilities in the Disko Bugt Area, West Greenland, in Phase With δ18O Oscillations at Camp Century. Paleoceanography and Paleoclimatology 33: 227-243.
Arrigo, K. and van Dijken, G. (2015). Continued increases in Arctic Ocean primary production, Progress in Oceanography 136, 60-70.
Comiso, J.C., 2012: Large Decadal Decline of the Arctic Multiyear Ice Cover. J. Climate, 25, 1176–1193.
Cormier MA, Rochon A, de Vernal A, et al. (2016) Multi-proxy study of primary production and paleoceanographical conditions in northern Baffin Bay during the last centuries. Marine Micropaleontology 127: 1-10.
Crawford DW, Cefarelli AO, Wrohan IA, et al. (2018) Spatial patterns in abundance, taxonomic composition and carbon biomass of nano- and microphytoplankton in Subarctic and Arctic Seas. Progress in Oceanography 162: 132-159.
de Vernal A and Marret F. (2007) Organic-Walled Dinoflagellate Cysts: Tracers of Sea-Surface Conditions. Development in Marine Geology 1: 371-408.
de Vernal A, Rochon A, Fréchette B, et al. (2013) Reconstructing past sea ice cover of the Northern Hemisphere from dinocyst assemblages: status of the approach. Quaternary Science Reviews 79: 122-134.
Guiot J and de Vernal A. (2007) Chapter Thirteen Transfer Functions: Methods for Quantitative Paleoceanography Based on Microfossils. In: Hillaire-Marcel C and De Vernal A (eds) Proxies in Late Cenozoic Paleoceanography. 523-563.
Kohlbach D, Graeve M, A. Lange B, et al. (2016) The importance of ice algae-produced carbon in the central Arctic Ocean ecosystem: Food web relationships revealed by lipid and stable isotope analyses. Limnology and Oceanography 61: 2027-2044.
Limoges A, Ribeiro S, Weckström K, et al. (2018) Linking the Modern Distribution of Biogenic Proxies in High Arctic Greenland Shelf Sediments to Sea Ice, Primary Production, and Arctic-Atlantic Inflow. Journal of Geophysical Research: Biogeosciences 123: 760-786.
Marret F and Zonneveld KAF. (2003) Atlas of modern organic-walled dinoflagellate cyst distribution. Review of Palaeobotany and Palynology 125: 1-200.
Matthiessen J, Schreck M, De Schepper S, et al. (2018) Quaternary dinoflagellate cysts in the Arctic Ocean: Potential and limitations for stratigraphy and paleoenvironmental reconstructions. Quaternary Science Reviews 192: 1-26.