Browsing by Author "Mohamed, Fwziah Ali Abdalali"

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    Identifying Zinc Inputs to Heard and McDonald Islands Region using Zinc Concentrations and Isotopic Compositions
    (2020-08-24) Mohamed, Fwziah Ali Abdalali; Wieser, Michael E.; Yang, Lu; Hobill, David W.; Yau, Andrew W.; Mayer, Bernhard
    Zinc (Zn) availability in the ocean is thought to have the potential to impact the health and the biomass of phytoplankton communities in the ocean. The application of Zn isotopic composition is an effective approach to understand sources and environmental receptors of Zn in the ocean. An important challenge; however, is to measure the Zn isotopic composition reliably because of the limited range in Zn isotopic composition and the low amount of Zn found in the ocean. Zinc is a micronutrient that has received much attention due to its role in the biology of marine phytoplankton. Ocean surface water Zn concentrations are in the low nanomolar range, potentially limiting the growth of some phytoplankton species. Identifying and assessing Zn sources in the ocean can provide insights into the significance and the influence of Zn availability on phytoplankton growth. This thesis research project entails the development of a reliable method to explore the Zn sources in the vicinity of Heard and McDonald Islands, an Australian territory, in the Southern Ocean. The region of Heard and McDonald Islands, two of the most active volcanic islands in the world, is one of the regions in the Southern Ocean where large phytoplankton blooms are produced annually. This raises the possibility that the islands’ hydrothermal activity is releasing large amounts of trace elements including Zn to the water column thereby enhancing the biological productivity in the region. The development of the analytical method included a careful consideration of all factors that may affect Zn measurements, including Zn laboratory blanks introduced during the sample handling and preparation, isobaric interferences from the sample matrix, and the data reduction technique. Zinc concentrations and isotopic compositions were measured in seawater, suspended particles, sediments, and rock samples collected during the Heard Earth Ocean Biosphere Interactions (HEOBI) voyage in January and February of 2016 led by the Institute for Marine and Antarctic Studies (IMAS) at the University of Tasmania, Australia. Zinc concentrations and isotope amount ratio data indicated that; a possible Zn hydrothermal component may have been influencing the waters near McDonald Island and at a couple of stations in the waters surrounding Heard Island. A more definitive indication of possible Zn hydrothermal sources in the waters surrounding Heard and McDonald Islands could be possible if additional data including Zn excess and the concentration of mantle helium become available.