Unravelling the potential of Trace elements in ostracodes as environmental paleoproxies in Hong Kong marine ecosystem.
Dr Not, Christelle Aurelie (Principal investigator)
Dr Yasuhara Moriaki (Co-Investigator)
Ostracodes, Proxy development, Paleoenvironment, Trace elements, Hong Kong
Others - Physical Sciences,Environmental Studies and Science
Block Grant Earmarked for Research (104)
HKU Project Code
Seed Funding Programme for Basic Research
Ostracodes are microscopic benthic crustaceans, which grow by moulting of their calcite valves and therefore the elemental shell chemistry represent the chemistry of the surrounding water at the specific time of valve formation. In addition, ostracodes are less susceptible to intra-shell diagenetic contamination due to their open, chamber free shells. Therefore ostracodes are a robust recorder of deep-sea environment and water. Trace elements content in calcitic shells has been an important tool for paleoenvironmental reconstruction. The reconstruction of past bottom water temperature has been the focus on many recent studies, which used the correlation between the water temperature and Mg/Ca of calcium carbonate shell organisms as benthic foraminifera and ostracodes (Yu and Elderfield, 2008; Chivas et al, 1985; Chivas et al, 1986; Dwyer et al., 2001). In addition to Mg/Ca other trace elements such as Sr/Ca or B/Ca have been used as a carbonate chemistry proxy in benthic foraminifera (Rosenthal et al., 2006; Rathmann and Kuhnert, 2008). The Mg content of marine ostracodes is higher than those of benthic foraminifera and is suggested to be less sensitive to carbonate ion effects (Farmer et al., 2012) indicating that bottom water reconstruction based on marine ostracodes is possibly more straightforward than benthic foraminifera-based reconstruction. However, the possibility of using other traces elements in marine ostracodes as environmental proxy was only barely investigated principally due the lack of understanding of their behaviour in vivo (i.e. vital effects related to: genus, species shell size, intra-shell heterogeneity etc.). Although lab experiment and field studies on the composition of freshwater ostracode shells indicated the potential for environmental reconstruction based on various trace element ratios (Chivas et al, 1986; De Deckker et al., 1998, 1999) their use in marine environment received much less attention. Here, we propose to develop a modern calibration dataset of various trace element ratios (Mg/Ca, Sr/Ca, Na/Ca, Ba/Ca, B/Ca and Cd/Ca) in marine ostracode shells to use them to reconstruct shallow-marine environment from the recent past (century scale) to the Cenozoic time scale (the last 65My). By combining the marine water quality monitoring data base of the Environmental Protection Department of the Hong Kong Special Administrative Region (HK SAR) with the measurement of several trace element ratios in ostracode shells from the sediment located near the monitoring stations, we aim to develop new proxies to reconstruct environmental parameters such as temperature, salinity, pH, dissolved oxygen and nutrient. Therefore the proposed project overachieving objective is to develop the first modern calibration of trace elements content in marine ostracodes in relation to their living environment and its physical and chemical properties.