Browsing by Author "Harington, Amy"

Now showing 1 - 4 of 4
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    Biophysical interactions in the Iceland Basin
    (2008) Harington, Amy; Lucas, Michael I
    The Iceland Basin in the N. Atlantic has attracted considerable recent attention because the spring bloom in this region acts as the most powerful biological carbon pump anywhere in the world oceans. Furthermore, the link between primary productivity and herbivory by the calanoid copepod, Calanus finmarchicus provides the trophic link between primary producers and the important commercial fishery for Atlantic Cod. However, one result of ocean warming is that the distribution of the cold water loving Calanus finmarchicus is being pushed northwards which adversely affects the food supply to juvenile Cod. Perhaps of more serious concern are concerns that the biological carbon pump may weaken as a result of increased thermal stratification and therefore reduce upward nitrate flux to drive nitrate-based export production. This was in fact confirmed at least in the study region which is dominated by regenerated production (f-ratio <0.5) which in turn suggests a shift in community structure from larger celled organisms to smaller celled organisms, characterised by long inefficient food chains. This project makes use of summer cruise data to the Iceland Basin last summer (2007) where measurements of 15N derived new production (NP) were made to add to previous seasonal (spring, winter) measurements of NP in the region.
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    Mineralised phytoplankton community composition in the Scotia and Weddell seas (Southern Ocean), with emphasis on diatoms and coccolithophores Amy Harington.
    (2012) Harington, Amy; Lucas, Mike; Poulton, Alex
    Phytoplankton community composition in the Southern Ocean (SO) determines levels of primary production, which support marine ecosystems and export of material to the deep sea. Nanoplankton (cell diameters 2-20 μm) are poorly resolved by traditional microscopy, and it is becoming apparent that unknown diversity and ecosystem functionality may be contained in this size class: for example, small diatoms (< 10 μm) appear widespread in the SO, and may limit our understanding of the response of phytoplankton communities to climate change.
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    Trace metal effects on phytoplankton in subpolar seas with special emphasis on coccolithophores
    (2017) Harington, Amy; Poulton, Alex; Lucas, Michael I; Moloney, Coleen L
    Coccolithophores are a biogeochemically important phytoplankton group, fulfilling an important role in the global carbon cycle through primary production and the formation and export of calcium carbonate. Despite this biogeochemical importance, relatively little is known about their ecophysiology, for example their response to nutrient availability in terms of both macronutrient (nitrate, phosphate) and micronutrient (trace metal) or how this impacts on their competition with other phytoplankton groups (e.g. diatoms, Synechococcus). Hence, this study investigated the response of coccolithophores to trace metal (iron, zinc and cobalt) additions in the high latitude North Atlantic (Iceland and Irminger basins) and the Southern Ocean (Great Calcite Belt, Scotia Sea). The response of coccolithophores to environmental conditions was investigated by examining distribution patterns in situ and in targeted bioassays where natural communities were incubated with elevated levels of trace metal concentration. The wide range of initial conditions for these bioassays (e.g. temperature, macro- and micro-nutrient availability and phytoplankton community composition), provided valuable insights into coccolithophore responses to trace metal addition across a range of different biogeographic regions. These responses were investigated in terms of coccolithophore cell abundances, species composition, calcite production and growth rates, and were contrasted with responses of the total phytoplankton community (chlorophyll α) and abundances of diatoms and other phytoplankton groups (e.g. Synechococcus). The major finding of this thesis is that iron addition positively enhances coccolithophore growth rates and calcite production in both the Northern and Southern subpolar oceans. Another significant finding was that zinc addition also positively enhanced growth rates of coccolithophores (and diatoms) in a number of bioassays across the Great Calcite Belt (Southern Ocean). Thus, the trace metals iron and zinc are important micronutrients to consider in regulating coccolithophore growth and calcite production. As climate change potentially altering the flux of such trace metals to the ocean it is therefore important to further investigate the role of these micronutrients in regulating coccolithophore communities and their biogeochemical impact.
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    What are the biogeochemical consequences of heuweltjie formation?
    (2008) Harington, Amy; Midgley, Jeremy J
    This study was to determine whether the basal calcrete layer of heuweltjies derives its nutrients from local or exotic sources and also to estimate relative rates of deposition and an approximate age of the heuweltjie. By calculating deposition rates and by using data from Soderberg and Compton [1998] heuweltjies were found to be much older than previous research has indicated ~95 000 years old. ⁸⁷/⁸⁶Sr isotope ratios of on-mound and off-mound soils indicate that the majority of the nutrients are exotically derived. However, it is important to note that there are various different sources which could have contributed to the mound and that it could not be determined what sources had contributed in what proportions. It was determined through a simple mixing model that approximately 90% of the nutrients are derived from marine aerosol.