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The distribution of dissolved molybdenum along the 30˚ E meridian (GEOTRACES Process Study (GIpr07)): First assessment of the factors affecting its behaviour in the African sector of the Southern Ocean
Thesis (MSc)--Stellenbosch University, 2021.
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Stellenbosch : Stellenbosch University
2021
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| _version_ | 1867613991596982272 |
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| access_status_str | Open Access |
| author | Mkandla, Andile |
| author2 | Roychoudhury, Alakendra N. |
| author_browse | Mkandla, Andile Roychoudhury, Alakendra N. |
| author_facet | Roychoudhury, Alakendra N. Mkandla, Andile |
| author_sort | Mkandla, Andile |
| collection | Thesis |
| dc_rights_str_mv | Stellenbosch University |
| description | Thesis (MSc)--Stellenbosch University, 2021. |
| format | Thesis |
| id | oai:scholar.sun.ac.za:10019.1/123826 |
| institution | Stellenbosch University (South Africa) |
| language | en_ZA |
| last_indexed | 2026-06-10T12:44:55.985Z |
| license_str | Other — see source repository |
| provenance_str_mv | Harvested via OAI-PMH from SUNScholar — Stellenbosch University Repository |
| publishDate | 2021 |
| publishDateRange | 2021 |
| publishDateSort | 2021 |
| publisher | Stellenbosch : Stellenbosch University |
| publisherStr | Stellenbosch : Stellenbosch University |
| record_format | dspace |
| source_str | SUNScholar — Stellenbosch University Repository |
| spelling | oai:scholar.sun.ac.za:10019.1/123826 The distribution of dissolved molybdenum along the 30˚ E meridian (GEOTRACES Process Study (GIpr07)): First assessment of the factors affecting its behaviour in the African sector of the Southern Ocean Mkandla, Andile Roychoudhury, Alakendra N. Stellenbosch University. Faculty of Science. Dept. of Earth Sciences. Dissolved molybdenum -- Africa -- Southern Ocean Phytoplankton -- Adaptation -- Southern Ocean Molybdenum enzymes -- Analysis Atmospheric deposition -- Africa -- Southern Ocean GEOTRACES UCTD Thesis (MSc)--Stellenbosch University, 2021. ENGLISH ABSTRACT: Molybdenum (Mo) is considered an essential micronutrient owing to its vital role as a cofactor of enzymes facilitating the nitrogen metabolism in phytoplankton. Owing to its unreactive nature in seawater, Mo remains understudied in the oceans. This study presents the first characterisation of dissolved Mo obtained from the seven stations between 41° S and 58° S along the 30° E meridian in the African sector of the Southern Ocean. A sum of 125 samples were collected and analysed for dMo using an ICP-MS. Similar to previous reports, dMo data from this study showed a largely conservative behaviour with an average concentration of 114.16 ± 3.59 nM (n = 125). The minor variations of dMo were mostly eliminated by normalising dMo concentrations to in-situ salinity. Further, a constant molybdenum to salinity ratio (0.30 ± 0.01), similar to that of north Atlantic Ocean reinforced oceanic mixing as the dominant factor controlling the behaviour of Mo in the Southern Ocean. Interestingly, an anomalous case was observed in TM8 (43⁰ S), where dMo enrichment of about 6% higher than mean concentrations occurred on the surface, implying an external dMo input. Hysplit models supported by latest literature, suggested inputs by atmospheric depositions – natural and/or anthropogenic – from continental margins. Similar dMo enrichments observed in deeper waters (AABW and LCDW) are thought to be as a result of accumulation with time. Also, deep water mixing enables the advection of dMo from AABW and LCDW towards the NADW. I further observed dMo depletions from station adjacent to the mid-Indian ocean ridge likely due to scavenging by pFe and pMn. Finally, despite the fact that Mo is known to be required by marine organism, dMo profiles from our data did not show any changes analogous to biological processes on the surface waters, further reinforcing the notions supporting its conservative behaviour. KEY WORDS: Dissolved molybdenum, conservative, African sector, Southern Ocean, GEOTRACES. ISISHWANKATHELO SESI XHOSA: I-Molybdenum (Mo) ithathwa njenge-micronutrient ebalulekileyo ngenxa yendima yayo ebalulekileyo njenge-cofactor ye-enzymes eququzelela i-nitrogen metabolism kwi- phytoplankton. Ngenxa yobume bayo obungasasebenziyo kumanzi olwandle, u-Mo uhlala ephantsi kolwandle. Olu phononongo lubonisa uphawu lokuqala lukaMo onyibilikileyo olufunyenwe kwizikhululo ezisixhenxe phakathi kwe-41 ° S kunye ne-58 ° S ecaleni kwe-30 ° E yecandelo le-Afrika loLwandlekazi lwaseMazantsi. Inani leesampulu eziyi-125 zaqokelelwa zaze zahlalutywa ze-dMo zisebenzisa i-ICP-MS. Ngokufana neengxelo zangaphambili, idatha ye-dMo kolu phononongo ibonise indlela yokuziphatha egcinakalayo ene-avareji ye-114.16 ± 3.59 nM (n = 125). Umahluko omncinci we-dMo ubukhulu becala ususwe ngokulungisa ukugxila kwe-dMo kwi-in-situ ityiwa. Ngaphaya koko, i-molybdenum engagungqiyo kwi-sality ratio (0.30 ± 0.01), efanayo naleyo yomantla oLwandlekazi lweAtlantic iqinise ukuxubana kolwandle njengeyona nto iphambili kulawulo lokuziphatha kukaMo kuLwandlekazi lwaseMazantsi. Into enomdla kukuba, imeko engathandekiyo yaqwalaselwa kwi-TM8 (43⁰ S), apho i-dMo ityebisa malunga ne-6% ephezulu kunokubonisa ubungakanani bokwenzeka komhlaba, okuthetha ukuba negalelo langaphandle le-dMo. Iimodeli zeHysplit ezixhaswe luncwadi lwamva nje, amagalelo aphakanyisiweyo ngofakelo lomoya-wendalo kunye / okanye i-anthropogenic - ukusuka kwimida yelizwekazi. Ukwandiswa okufanayo kwe-dMo kuqatshelwe emanzini anzulu (i-AABW kunye neLCDW) kucingelwa ukuba kungumphumo wokuqokelela ixesha. Kwakhona, ukuxubana kwamanzi anzulu kwenza ukubhengezwa kwe-dMo ukusuka kwi-AABW kunye neLCDW ukuya kwi-NADW. Siphinde sajonga ukuphulukana kwe-dMo ukusuka kwisikhululo esikufutshane kumbindi wolwandlekazi lwaseIndiya ngokunokwenzeka ngenxa yokuhluthwa yi- pFe kunye ne-pMn. Okokugqibela, ngaphandle kwento yokuba uMo uyaziwa ukuba uyafuneka kwizinto eziphilayo zaselwandle, iiprofayili ze-dMo ezivela kwidatha yethu azibonisanga lutshintsho luyeleleneyo kwiinkqubo zebhayiloji kumanzi angaphezulu, ukuqinisa ngakumbi umbono oxhasa isimilo sayo. AMAZWI ANGUNDOQO: molybdenum inyibilikisweyo, ulondolozo, Icandelo leAfrika, UMazantsi oLwandle, GEOTRACES AFRIKAANSE OPSOMMING: Molibdeen (Mo) word beskou as 'n noodsaaklike mikrovoedingstof vanweë sy belangrike rol as 'n kofaktor van ensieme wat die stikstofmetabolisme in fitoplankton vergemaklik. Vanweë die onreaktiewe aard daarvan in seewater, bly Mo steeds onderstudie in die oseane. Hierdie studie bied die eerste karakterisering van opgeloste Mo verkry uit die sewe stasies tussen 41 ° S en 58 ° S langs die 30 ° E meridiaan in die Afrika -sektor van die Suidelike Oseaan. 'N Som van 125 monsters is versamel en geanaliseer vir dMo met behulp van 'n ICP-MS. Soortgelyk aan vorige verslae, het dMo -data uit hierdie studie 'n grootliks konserwatiewe gedrag getoon met 'n gemiddelde konsentrasie van 114,16 ± 3,59 nM (n = 125). Die geringe variasies van dMo is meestal uitgeskakel deur dMo-konsentrasies te normaliseer tot in-situ soutgehalte. Verder het 'n konstante molibdeen tot soutgehalte verhouding (0.30 ± 0.01), soortgelyk aan dié van die Noord -Atlantiese Oseaan, die oseaanse vermenging versterk as die dominante faktor wat die gedrag van Mo in die Suidelike Oseaan beheer. Interessant genoeg is 'n afwykende geval waargeneem in TM8 (43⁰ S), waar dMo -verryking van ongeveer 6% hoër as die gemiddelde konsentrasies op die oppervlak plaasgevind het, wat 'n eksterne dMo -inset impliseer. Hysplit -modelle ondersteun deur die nuutste literatuur, voorgestelde insette deur atmosferiese afsettings - natuurlik en/of antropogeen - vanaf kontinentale marges. Daar word vermoed dat soortgelyke dMo -verryking in dieper waters (AABW en LCDW) waargeneem word as gevolg van opeenhoping met tyd. Diepwatermenging maak ook dit moontlik om dMo van AABW en LCDW na die NADW te beweeg. Ons het verder dMo-uitputting waargeneem vanaf die stasie aangrensend aan die middel-Indiese oseaanrand, waarskynlik as gevolg van opruiming deur pFe en pMn. Ten slotte, ten spyte van die feit dat Mo bekend is dat dit deur die mariene organisme benodig word, het dMo -profiele uit ons data geen veranderings getoon wat analoog is aan biologiese prosesse op die oppervlakwater nie, wat die konsepte wat sy konserwatiewe gedrag ondersteun, verder versterk het. SLEUTELWOORDE: Opgeloste molibdeen, konserwatief, Afrika -sektor, Suidelike Oseaan, GEOTRACES Masters 2021-11-24T16:32:49Z 2021-12-22T14:23:39Z 2021-11-24T16:32:49Z 2021-12-22T14:23:39Z 2021-12 Thesis http://hdl.handle.net/10019.1/123826 en_ZA Stellenbosch University x, 68 pages : illustrations (some color), maps application/pdf Stellenbosch : Stellenbosch University |
| spellingShingle | Dissolved molybdenum -- Africa -- Southern Ocean Phytoplankton -- Adaptation -- Southern Ocean Molybdenum enzymes -- Analysis Atmospheric deposition -- Africa -- Southern Ocean GEOTRACES UCTD Mkandla, Andile The distribution of dissolved molybdenum along the 30˚ E meridian (GEOTRACES Process Study (GIpr07)): First assessment of the factors affecting its behaviour in the African sector of the Southern Ocean |
| title | The distribution of dissolved molybdenum along the 30˚ E meridian (GEOTRACES Process Study (GIpr07)): First assessment of the factors affecting its behaviour in the African sector of the Southern Ocean |
| title_full | The distribution of dissolved molybdenum along the 30˚ E meridian (GEOTRACES Process Study (GIpr07)): First assessment of the factors affecting its behaviour in the African sector of the Southern Ocean |
| title_fullStr | The distribution of dissolved molybdenum along the 30˚ E meridian (GEOTRACES Process Study (GIpr07)): First assessment of the factors affecting its behaviour in the African sector of the Southern Ocean |
| title_full_unstemmed | The distribution of dissolved molybdenum along the 30˚ E meridian (GEOTRACES Process Study (GIpr07)): First assessment of the factors affecting its behaviour in the African sector of the Southern Ocean |
| title_short | The distribution of dissolved molybdenum along the 30˚ E meridian (GEOTRACES Process Study (GIpr07)): First assessment of the factors affecting its behaviour in the African sector of the Southern Ocean |
| title_sort | distribution of dissolved molybdenum along the 30˚ e meridian geotraces process study gipr07 first assessment of the factors affecting its behaviour in the african sector of the southern ocean |
| topic | Dissolved molybdenum -- Africa -- Southern Ocean Phytoplankton -- Adaptation -- Southern Ocean Molybdenum enzymes -- Analysis Atmospheric deposition -- Africa -- Southern Ocean GEOTRACES UCTD |
| url | http://hdl.handle.net/10019.1/123826 |
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