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Understanding Southern Ocean phytoplankton ecophysiological response to iron availability
Thesis (PhD)--Stellenbosch University, 2022.
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| Format: | Thesis |
| Language: | en_ZA |
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Stellenbosch : Stellenbosch University
2022
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| _version_ | 1867613916609118208 |
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| access_status_str | Open Access |
| author | Singh, Asmita |
| author2 | Ryan-Keogh, Thomas |
| author_browse | Ryan-Keogh, Thomas Singh, Asmita |
| author_facet | Ryan-Keogh, Thomas Singh, Asmita |
| author_sort | Singh, Asmita |
| collection | Thesis |
| dc_rights_str_mv | Stellenbosch University |
| description | Thesis (PhD)--Stellenbosch University, 2022. |
| format | Thesis |
| id | oai:scholar.sun.ac.za:10019.1/124657 |
| institution | Stellenbosch University (South Africa) |
| language | en_ZA |
| last_indexed | 2026-06-10T12:43:44.982Z |
| license_str | Other — see source repository |
| provenance_str_mv | Harvested via OAI-PMH from SUNScholar — Stellenbosch University Repository |
| publishDate | 2022 |
| publishDateRange | 2022 |
| publishDateSort | 2022 |
| publisher | Stellenbosch : Stellenbosch University |
| publisherStr | Stellenbosch : Stellenbosch University |
| record_format | dspace |
| source_str | SUNScholar — Stellenbosch University Repository |
| spelling | oai:scholar.sun.ac.za:10019.1/124657 Understanding Southern Ocean phytoplankton ecophysiological response to iron availability Singh, Asmita Ryan-Keogh, Thomas Fietz, Susanne Thomalla, Sandy Stellenbosch University. Faculty of Science. Dept. of Earth Sciences. Fluorescence Phytoplankton -- Photophysiology Marine phytoplankton -- Effect of iron on -- Southern Ocean Phytoplankton -- Ecophysiology -- Southern Ocean Iron-limited Fast Repetition Rate fluorometry Photosynthetic efficiency (Fv/Fm) Trace metals Biogeochemistry -- Antarctic Ocean -- Southern Ocean Climatic changes -- Antarctic Ocean -- Southern Ocean Marine plants --Effect of atmospheric carbon dioxide on UCTD Thesis (PhD)--Stellenbosch University, 2022. ENGLISH ABSTRACT: Over the past century, climate change has been of growing concern, due to its ecological and economic global impact. The Southern Ocean buffers the impacts of climate change by accounting for a significant proportion of the total oceanic uptake of CO2. Phytoplankton primary production and carbon export (the biological carbon pump) plays an important role in the Southern Ocean carbon cycle and despite their ability to remove a significant amount of the global organic carbon flux each year, it is often constrained by the availability of light and nutrients. The micronutrient iron is particularly important in the production of key metabolic and photosynthetic proteins in phytoplankton and its scarcity in the Southern Ocean dictates its role as a key driver of variability in Southern Ocean productivity. A greater understanding of the response of Southern Ocean phytoplankton to seasonal and regional variability to their environmental drivers (with a focus on iron in particular) is thus required in order to increase the accuracy in assessing and predicting the impact of climate change. Active chlorophyll-a fluorescence is a non-invasive, powerful instantaneous tool, which can assess the phytoplankton photosynthetic efficiency in response to potential environmental drivers and in particular under stressful growth conditions, i.e. under iron limitation. However, our understanding of the seasonal cycle of photophysiological responses of phytoplankton to iron and other biogeochemical drivers remains limited, primarily due to the prevalence of experiments and measurements only being conducted in summer. In this research, three individual studies of phytoplankton photophysiology across all seasons of the Atlantic Southern Ocean were used to investigate physical and biogeochemical drivers of inter-zonal, inter-annual and intra-seasonal variability in phytoplankton photophysiology (Fv/Fm) in summer. Results from this study point to a combination of drivers (notably sea surface temperature, macronutrients and community structure) that elicit simultaneous and oftentimes antagonist responses in Fv/Fm, making it difficult to ascertain one dominant driver over another. In addition, the degree of iron stress in the Sea-Ice Zone in autumn, and the full zonal extent of the open Atlantic Southern Ocean in spring and winter, was determined using a series of short-term (24 hrs) in situ iron addition experiments. Key results suggest that phytoplankton in the Sea-Ice Zone of Dronning Maud Land are not iron-limited in autumn, and presumably have a sufficient year-round supply of iron potentially from shallow topography. However, both winter and spring showed some positive responses to iron addition with zonal variability being linked to the timing of the incubation experiments relative to the seasonal cycle of the mixed layer depth, highlighting the importance of convective overturning as a dominant seasonal iron supply mechanism. The research presented in this thesis contributes to a greater understanding of the complex interplay of multiple drivers of phytoplankton photosynthesis across the seasonal cycle. It is recommended that future research continues to address seasonal and regional variability in phytoplankton photophysiology but with a focus on resolving the relationship between multiple drivers in line with anticipated climate-mediated adjustments in environmental conditions. AFRIKAANSE OPSOMMING: Oor die afgelope eeu, word klimaat verandering ‘n groot bekommernis as gevolg van die globale ekologiese en ekonomiese impak. ‘n Aansienlike gedeelte van die totale opname van koolstofdioksied kan aan die Suidelike Oseaan wat die impak van klimaat verandering buffer toegeskryf word. Fitoplankton se primêre produksie en koolstof uitvoer (die biologiese koolstof pomp) speel ‘n belangrike rol in die Suidelike Oseaan koolstof siklus. Ten spyte van fitoplankton se vermoë om aansienlike hoeveelheede globale organiese koolstof oorskakel jaarliks te verwyder, word dit gereeld deur die beskikbaarheid van lig en voedingstowwe beperk. Die mikrovoedingstof yster is veral belangrik in die produksie van sleutel metabolise- en fotosintetiese fitoplankton protiene. Die skaarsheid van yster in die Suidelike Oseaan stel sy rol as ‘n belangrike kontrole van verandering in Suidelike Oseaan produktiwiteit vas. Om die asseseeringakuraatheid en impakbepaaling van Suidelike Oseaan fitoplankton op klimaat verandering te verbeter, is dit dus nodig om hul reaksie met beduidende kontrole, (yster) beide seisoenaal en streeksgewys beter te verstaan. Aktiewe chlorofil-a fluoresie is ‘n omvattende, nie-indringende en onmiddellike hulpmiddel, wat die fitoplankton fotosintetiese-effektiwiteit se reaksie met potentieel beduidende beheermaatreëls (spesifiek op gestresde groeitoestande, n.l. onder yster limitasie), kan asseseer. Egter, ons begrip van die seisoenaale siklus van fitoplankton fotofisiologiese reaksies as gevolg van yster en ander biogeochemiese kontrole bly beperk, in besonders, as gevolg van eksperimente en metings wat hoofsaklik in die somer uitgevoer is. In hierdie navorsing, word drie individuele studies van fitoplankton fotofisiologie oor alle seisoene in die Atlantise Suidelike Oseaan uitgevoer en die fisiese en biogeochemiese beheermaatreëls vir sones, jare en seisoenale veranderinge in fitoplanktonfotofisiologie (Fv/Fm) in die somer word bestudeer. Die resultate van die studie dui op n kombinasie van beheermaatreëls (hoofsaaklik see temperatuur, makro-voedingstowwe en gemeenskaps- strukture) wat gelyktydige en gereeld antagonistiese reaksies tot Fv/Fm het. Dus is die hoofsaaklike beheermaatreëls moeilik om te bepaal. Vervolgens, is die herfs See-Yssone, lente en winter oor die volle Atlantiese Suidelike Oseaan ysterstresvlakke deur kort-termyn (24 uur) in situ yster-toevoeging-experimente bepaal. Noodsaaklike resultate stel voor dat fitoplanton in die See-Yssone van Dronning Maud Land nie in die herfs ‘n yster-tekort ervaar nie en vermoedelik toegang tot ‘n voldoende voorraad yster deur die jaar kry, moontlik as gevolg van die vlak topografie. Beide lente en winter het egter positiewe reaksies tot yster-toevoeging getoon, met sonale variasie aan die tydsberekening van die inkubasie eksperimente gekoppel, relatief tot die seisoenale-siklus van die gemengde-vlak-diepte. Dit beklemtoon die belangrikheid van konveksie omslaan as ‘n dominante seisoenale yster-voorraad-meganisme. Die navorsing wat in die tesis getoon word dra by tot ‘n verbetering in die begrip van die komplekse interaksie van verskeie beheermaatreëls van fitoplanktonfotosintese oor die seisoenale-siklus. Daar word voorgestel dat toekomstige navorsing om the seisoenale en omgewingsverskille in fitoplanktonfotofisiologie te ondersoek voortgaan, veral om op die verwantskap tussen onderskeie beheermaatreëls met verwagte klimaat-gemedieerde veranderinge in omgewingstoestande te fokus. Doctoral 2022-03-08T23:03:25Z 2022-04-29T09:24:52Z 2022-03-08T23:03:25Z 2022-04-29T09:24:52Z 2022-04 Thesis http://hdl.handle.net/10019.1/124657 en_ZA Stellenbosch University xxv, 124 pages : illustrations (some color) application/pdf Stellenbosch : Stellenbosch University |
| spellingShingle | Fluorescence Phytoplankton -- Photophysiology Marine phytoplankton -- Effect of iron on -- Southern Ocean Phytoplankton -- Ecophysiology -- Southern Ocean Iron-limited Fast Repetition Rate fluorometry Photosynthetic efficiency (Fv/Fm) Trace metals Biogeochemistry -- Antarctic Ocean -- Southern Ocean Climatic changes -- Antarctic Ocean -- Southern Ocean Marine plants --Effect of atmospheric carbon dioxide on UCTD Singh, Asmita Understanding Southern Ocean phytoplankton ecophysiological response to iron availability |
| title | Understanding Southern Ocean phytoplankton ecophysiological response to iron availability |
| title_full | Understanding Southern Ocean phytoplankton ecophysiological response to iron availability |
| title_fullStr | Understanding Southern Ocean phytoplankton ecophysiological response to iron availability |
| title_full_unstemmed | Understanding Southern Ocean phytoplankton ecophysiological response to iron availability |
| title_short | Understanding Southern Ocean phytoplankton ecophysiological response to iron availability |
| title_sort | understanding southern ocean phytoplankton ecophysiological response to iron availability |
| topic | Fluorescence Phytoplankton -- Photophysiology Marine phytoplankton -- Effect of iron on -- Southern Ocean Phytoplankton -- Ecophysiology -- Southern Ocean Iron-limited Fast Repetition Rate fluorometry Photosynthetic efficiency (Fv/Fm) Trace metals Biogeochemistry -- Antarctic Ocean -- Southern Ocean Climatic changes -- Antarctic Ocean -- Southern Ocean Marine plants --Effect of atmospheric carbon dioxide on UCTD |
| url | http://hdl.handle.net/10019.1/124657 |
| work_keys_str_mv | AT singhasmita understandingsouthernoceanphytoplanktonecophysiologicalresponsetoironavailability |