The role of zooplankton in the biological carbon pump of the subantarctic Southern Ocean
Initiatives to study the impact of climate change on carbon sequestration in the subantarctic Southern Ocean have led to regular research voyages and the establishment of long-term moorings at the Southern Ocean Time Series site (47°S, 140°E) in the region. The subantarctic zone plays an important r...
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| Format: | Thesis |
| Language: | English |
| Published: |
2022
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| Online Access: | https://eprints.utas.edu.au/47565/ https://eprints.utas.edu.au/47565/1/Halfter_whole_thesis.pdf |
| Summary: | Initiatives to study the impact of climate change on carbon sequestration in the subantarctic Southern Ocean have led to regular research voyages and the establishment of long-term moorings at the Southern Ocean Time Series site (47°S, 140°E) in the region. The subantarctic zone plays an important role in the physical uptake and sequestration of carbon dioxide due to the formation and subduction of water masses. However, while extensively studied in other parts of the world's ocean, the biological production, transformation, and transport of particulate material is not well documented for the subantarctic zone. In particular, the role of zooplankton in the biological gravitational, mesopelagic-migrant, and seasonal lipid pumps has received less attention. Current knowledge gaps extend across zooplankton species composition in subsurface waters and its seasonal development, zooplankton mortality that leads to downward carbon ux by carcasses and quantification of zooplankton respiration in the water column. This thesis synthesises information on zooplankton and biogeochemistry in the subantarctic Southern Ocean to study the zooplankton-mediated carbon pump, including data from samples collected by deep-sea sediment traps, on field campaigns and from laboratory measurements. The thesis is composed of a general introduction (Chapter 1), a literature review (Chapter 2), three analysis chapters (Chapter 3-5) and a discussion, containing synthesis and future research priorities (Chapter 6). The second chapter reviews the role of zooplankton in establishing characteristic carbon export regimes in the Southern Ocean. Two case studies, the Kerguelen Plateau (high productivity, relatively low export) and the High-Nutrient Low-Chlorophyll waters south of Australia (low primary productivity, relatively high downward export), illustrate the importance of the zooplankton community composition, biomass and grazing for downward carbon export. The third chapter presents a long-term time-series (>20 years) of deep-sea ... |
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