Testing potential drivers for carbon isotopic signature of particulate organic carbon in the Southern Ocean
| dc.contributor.advisor | Fietz, Susanne | en_ZA |
| dc.contributor.advisor | Joubert, Warren R. | en_ZA |
| dc.contributor.author | Jordaan, Zandria | en_ZA |
| dc.contributor.other | Stellenbosch University. Faculty of Science. Dept. of Earth Sciences. | en_ZA |
| dc.date.accessioned | 2020-11-25T13:05:47Z | |
| dc.date.accessioned | 2021-01-31T19:45:14Z | |
| dc.date.available | 2020-11-25T13:05:47Z | |
| dc.date.available | 2021-01-31T19:45:14Z | |
| dc.date.issued | 2020-12 | |
| dc.description | Thesis (MSc)--Stellenbosch University, 2020. | en_ZA |
| dc.description.abstract | ENGLISH ABSTRACT: The carbon cycle in the Southern Ocean (SO) plays a very important role for all life on earth as it regulates carbon fluxes, transport nutrients to marine organisms and it is linked to the amount of available oxygen in the atmosphere. The conditions driving the carbon cycle dramatically changed over the past few decades which directly effects marine phytoplankton. Phytoplankton are key role players in the marine food web as they utilize atmospheric carbon dioxide transported into the surface ocean through different chemical exchanges. Fractionation of stable carbon isotopes occurs during the biological uptake of inorganic carbon, although all the influential forces behind the fractionation are not yet fully understood. Here we examine the potential physical- and chemical driving factors for carbon isotopic signature of particulate organic carbon (δ13CPOC) in the surface water of the SO. Winter and summer results are compared along the Bonus Good Hope line as well as a section in the Indian Ocean. The aim is to determine potential influences of the physical- and chemical driving factors on phytoplankton δ13CPOC, because it is possible to measure δ13CPOC directly from underlying sediments. Understanding the driving factors of δ13CPOC, will help the interpretation of sedimentary δ13CPOC in paleo-reconstruction studies, such as reconstructing past atmospheric partial pressure of carbon dioxide (pCO2 concentrations). Our results indicate that silicic acid and nitrate concentrations (μM), cyanobacteria and diatoms contributions to total chl-a (%) and temperature (ºC) could potentially be primary driving factors of δ13CPOC during the summer along the Bonus Good Hope line, as all these factors are significantly correlated to δ13CPOC. Winter results in the Atlantic sector of the SO (Winter Cruise 2015) did not show any potential driving factor. This is in contrast with results found in the Indian sector of the SO (Winter Cruise 2017), where all four investigated macronutrients (silicic acid, nitrate, nitrite and phosphate), chl-a, seven phytoplankton groups’ contributions to total chl-a (%), temperature and salinity could potentially drive the carbon isotopic signature. In addition, available pCO2 data was used to determine whether pCO2 is related to δ13CPOC in the upper layer of the Southern Ocean. The pCO2 results obtained during the Winter Cruise 2017, in the Indian sector of the Southern Ocean, were the only cruise where pCO2 had a significant (negative) correlation with δ13CPOC, indicating increased fractionation related to increasing pCO2 concentrations. In conclusion, for both the Atlantic and Indian sector of the SO, possible drivers of δ13CPOC were identified. It is important to take note of the different biological- and environmental factors co-influencing those potential driving factors. Correlations may have been identified where similar distributions of two studied parameters have been driven by a third, common factor. Hence, further studies should be made to confirm which parameter or parameters definitely drives δ13CPOC. | en_ZA |
| dc.description.abstract | AFRIKAANSE OPSOMMING: Die koolstofsiklus in die Suidelike Oseaan (SO) speel 'n baie belangrike rol vir alle lewe op aarde, aangesien dit koolstof-uitruiling reguleer, voedingstowwe na mariene organismes vervoer en dit is ook gekoppel aan die hoeveelheid beskikbare suurstof in die atmosfeer. Die toestande wat die koolstof siklus dryf, het dramaties verander oor die afgelope paar dekades wat ‘n direkte invloed op mariene fitoplankton het. Fitoplankton is sleutel rolspelers in die mariene voedselweb, aangesien hulle atmosferiese koolstofdioksied opneem wat deur verskillende chemiese uitruilingsprosesse in die boonste laag van die oseaan geplaas word. Fraksionering van stabiele koolstof isotope vind plaas tydens die biologiese opname van anorganiese koolstof, alhoewel al die invloedryke magte agter die fraksionering nie ten volle verstaan word nie. Hier ondersoek ons die potensiële fisiese - en chemiese dryffaktore vir koolstof isotopiese handtekening van spesifieke organiese koolstof (δ13CPOC) in die oppervlakwater van die SO. Winter en somer resultate word vergelyk langs die Goeie Hoop moniteringslyn sowel as 'n afdeling in die Indiese oseaan. Die doel is om potensiële invloede van die fisiese - en chemiese dryffaktore op fitoplankton δ13CPOC te bepaal, omdat dit moontlik is om δ13CPOC direk van onderliggende sedimente te meet. Daarom is dit belangrik om 'n dryffaktor te identifiseer waarin die verhouding gebruik kan word vir toekomstige paleo-rekonstruksiestudies, soos die rekonstruksie van voirige atmosferiese gedeeltelike druk van koolstofdioksied (pCO2) konsentrasies. Ons resultate dui daarop dat silikasuur en nitraatkonsentrasies (μM), sianbakterie en diatome se bydraes tot totale chl-a (%) en temperatuur (ºC) moontlik primêre dryffaktore van δ13CPOC gedurende die somer langs die Goeie Hoop moniteringslyn kan wees, aangesien al hierdie faktore beduidende korrelasie teenoor δ13CPOC toon. Winterresultate in die Atlantiese sektor van die SO (Wintervaart 2015) het nie enige potensiële dryffaktore getoon nie. Dit is in teenstelling met die resultate wat gevind is in die Indiese sektor (Wintervaart 2017), waar al vier makrovoedingstowwe (silikasuur, nitraat, nitriet en fosfaat), chl-a, sewe fitoplankton groepe se bydraes tot totale chl-a (%), temperatuur en soutgehalte moontlik die koolstof isotopiese handtekening kan dryf. Daarbenewens is beskikbare pCO2 data gebruik om te bepaal of pCO2 in die boonste laag van die SO verband hou met δ13CPOC. Die pCO2 resultate wat verkry is tydens die Wintervaart 2017, in die Indiese sektor van die SO, was die enigste vaart waar pCO2 'n beduidende (negatiewe) korrelasie met δ13CPOC toon, wat dui op verhoogde fraksionering wat verband hou met die verhoging van pCO2 konsentrasies. Ten slotte, vir beide die Atlantiese en Indiese sektor van die SO, is moontlike dryffaktore van δ13CPOC geïdentifiseer. Dit is belangrik om kennis te neem van die verskillende biologiese-en omgewingfaktore wat die potensiële dryffaktrore kan beïnvloed. Korrelasies kan geïdentifiseer word waar soortgelyke uitreikings van twee parameters wat hier bestudeer is, deur 'n derde, algemene faktor gedryf word. Juis om hierdie rede moet verdere studies gedoen word om te bevestig watter parameter of parameters defnitief die δ13CPOC dryf. | af_ZA |
| dc.format.extent | xvii, 114 pages : illustrations (some color) | en_ZA |
| dc.identifier.uri | http://hdl.handle.net/10019.1/109335 | |
| dc.language.iso | en_ZA | en_ZA |
| dc.language.iso | en_ZA | en_ZA |
| dc.publisher | Stellenbosch : Stellenbosch University | en_ZA |
| dc.rights.holder | Stellenbosch University | en_ZA |
| dc.subject | Aquaculture -- Effect of climatic changes on | en_ZA |
| dc.subject | Phytoplankton -- Indian Ocean | en_ZA |
| dc.subject | Atmospheric carbon dioxide -- Environmental aspects | en_ZA |
| dc.subject | Marine plants --Effect of atmospheric carbon dioxide on | en_ZA |
| dc.subject | Carbon -- Isotopes - Testing | en_ZA |
| dc.subject | UCTD | en_ZA |
| dc.title | Testing potential drivers for carbon isotopic signature of particulate organic carbon in the Southern Ocean | en_ZA |
| dc.type | Thesis | en_ZA |