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dc.contributor.advisorMarit, Reigstad
dc.contributor.authorBodur, Yasemin V.
dc.date.accessioned2024-06-11T10:18:38Z
dc.date.available2024-06-11T10:18:38Z
dc.date.embargoEndDate2025-06-28
dc.date.issued2024-06-28
dc.description.abstractThe biological carbon pump (BCP) is a major component of earth’s biogeochemical cycle. In the Arctic, increasing air temperatures, declining sea-ice cover, and increasing influence of boreal water masses and coastal runoff lead to changes in Arctic ecosystems, with consequences for the BCP. To get a holistic understanding of the BCP, it is important to integrate findings from disciplines that tackle different aspects of its functioning and possible response to climate change. In this thesis, the results from a benthic study on the Northeast Greenland shelf, a seasonal vertical flux study in the northwestern Barents Sea, and aggregation experiments in a sub-Arctic fjord are integrated to get a holistic understanding of some mechanisms of the BCP and pelagic-benthic coupling in the Arctic. The key findings of this thesis are: 1) on the Northeast Greenland shelf, benthic ecosystems depend on organic matter sinking from the pelagic, and pelagic-benthic coupling might have weakened since the 1990s; 2) in the northwestern Barents Sea; the composition of vertical flux between spring and summer differ highly from each other, with fresh, Chlorophyll-a-rich sinking particles dominated by diatoms during spring, and more regenerated particles sinking during summer, dominated by fecal pellets and flagellates. The efficiency of vertical flux is lower in summer compared to spring; 3) aggregation of dissolved organic matter (DOM) can be an important contributor to the particle pool, and this contribution changes seasonally, being higher in summer compared to spring. Integrating the findings of this thesis, some mechanisms of the BCP are summarized and pelagic-benthic coupling across different Arctic shelves are compared, concluding that the BCP will probably respond individually to climate change on the different Arctic shelves due to a range of mechanisms that control the BCP differently on regional levels.en_US
dc.description.abstractDen biologiske karbonpumpen er viktig for verdens biogeokjemiske syklus. I Arktis, økende lufttemperatur, avtagende havis og økende innflytelse av boreale vannmasser og kystavrenning skal ha konsekvenser for økosystemer og for karbonpumpen. For å få en omfattende forståelse av biologiske karbonpumpen, må vi integrere funn fra flere disipliner som behandler forskjellige aspekter av funksjonen og mulig respons av biologiske karbonpumpen til klimaendringene. I denne PhD oppgaven, resultatene fra en studie om bentiske samfunn i Nordøstgrønland, en studie om vertikalfluks i forskjellige sesonger i nordvestlige Barentshavet, og aggregasjonseksperimenter i en sub-arktisk fjord er innlemmet for å få en helhetlig forståelse av mekanismene i biologiske karbonpumpen og pelagisk-bentiske koblingen. Nøkkelfunnene er: 1) pelagisk-bentiske koblingen i Nordøstgrønland har trolig avtatt; 2) i nordvestlige Barentshavet, komposisjon av vertikalfluks er veldig forskjellig mellom vinter, vår og sommer. I våren sinker Chlorophyll-a-rike, diatomeen-dominerte partikler ut. I sommeren er partikler dominert av fekale og flagellater. Karbonpumpen er mindre effektivt i sommeren fordi det er flere partikler i vannsøylen, men vertikalfluks er ikke høyre enn i våren. 3) Aggregasjon av oppløst organiske material kan være et viktig bidrag til partikkel (pool), og dette bidraget endres sesongmessig, og er høyest i sommeren. I syntesen av denne oppgaven, forskjellige mekanismer av biologiske karbonpumpen er oppsummert og pelagisk-bentiske koblingen på tvers av ulike arktiske sokkel sammenlignes. For å konkludere, den biologiske karbonpumpen vil sannsynligvis reagere på forskjellige måter til klimaendringene på tvers av forskjellige arktiske sokkel, fordi en rekke mekanismer kontrollerer karbonpumpen på regionale nivåer.en_US
dc.description.doctoraltypeph.d.en_US
dc.description.popularabstractBillions of particles, known as marine snow, sink every day from the surface to the bottom of the ocean. This is one of the most important processes that helps the ocean remove carbon dioxide (CO2) from the atmosphere. If a large part of the carbon that we emit into the atmosphere were not removed by the ocean, the earth would be much warmer today. When CO2 dissolves in the ocean, it is consumed by tiny algae called phytoplankton. These organisms use CO2 and sunlight to grow through photosynthesis. They form the base of the oceanic food web and are consumed by a variety of marine organisms. The remnants of this food web, including dead phytoplankton and fecal pellets, aggregate into particles that sink, effectively packaging and transporting carbon to the seafloor. Upon reaching the seafloor, most of these particles are consumed by benthic animals. The abundance of seafloor animals can serve as an indicator of how much carbon reaches the depths, as more food supports larger populations. High-latitude regions, such as the Arctic, are especially efficient at transporting and removing carbon in the form of particles. However, climate change might be altering this efficiency. The Arctic is experiencing rapid temperature increases, sea ice loss, and stronger inflows of warmer water from the Atlantic and Pacific Oceans. With less sea ice, more light penetrates the ocean, potentially boosting phytoplankton growth. Yet, it's unclear if this will lead to increased carbon removal due to the complex mechanisms involved that regulate the quantity and quality of sinking particles. In my thesis, I studied benthic animals on the Northeast Greenland shelf and found a potential decline in the quantity or quality of sinking particles since the 1990s. To understand why, I examined sinking particles in the northern Barents Sea across different seasons in more detail. During spring, when sea ice is present, the particles are fresh. In summer, when sea ice has mostly retreated, there was more light and more particles overall, but fewer were sinking compared to spring. Moreover, the particles were smaller and less fresh, because other organisms feed on the particles, breaking them down and leaving less to sink. Additionally, by summer, most nutrients needed for phytoplankton growth are depleted. If summer-like conditions extend due to climate change, will this mean fewer particles sink, providing less food for seafloor animals? The answer is not straightforward. The Barents Sea and the Northeast Greenland shelf differ significantly; the Barents Sea receives nutrient-rich Atlantic waters, while the Northeast Greenland shelf is less nutrient-rich. In the Barents Sea, summer storms can mix particles deeper into the ocean, beyond the reach of many consumers. In contrast, the Northeast Greenland shelf has a stable layer of cold freshwater that may prevent such mixing, leading to more particle consumption in the upper layers. Other factors can influence particle sinking during summer. For example, fecal pellets from animals that feed on phytoplankton can sink rapidly. Dissolved carbon can aggregate, adding to the particle pool and increasing sinking chances. More dissolved carbon is present in the Arctic during summer, suggesting this process may dominate at that time. Additionally, materials like sand or clay, delivered by rivers, melting glaciers, or thawing permafrost, can add weight to particles, aiding their descent. The sinking of particles, and consequently the removal and storage of carbon, depends on a multitude of factors, which are likely to vary across different regions of the Arctic.en_US
dc.description.sponsorshipUiT Arven etter Nansen (RCN #276730)en_US
dc.identifier.isbn978-82-8266-263-5
dc.identifier.urihttps://hdl.handle.net/10037/33778
dc.language.isoengen_US
dc.publisherUiT The Arctic University of Norwayen_US
dc.publisherUiT Norges arktiske universiteten_US
dc.relation.haspart<p>Paper I: Bodur, Y.V., Renaud, P.E., Lins, L., Da Costa Monteiro, L., Ambrose Jr, W.G., Felden, J., Krumpen, T., Wenzhöfer, F., Włodarska-Kowalczuk, M. & Braeckman, U. (2024). Weakened pelagic-benthic coupling on an Arctic outflow shelf (Northeast Greenland) suggested by benthic ecosystem changes. <i>Elementa: Science of the Anthropocene ,12</i>(1), 00005. Also available in Munin at <a href=https://hdl.handle.net/10037/33764>https://hdl.handle.net/10037/33764</a>. <p>Paper II: Bodur, Y.V., Renaud, P.E., Goraguer, L., Amargant-Arumí, M., Assmy, P., Dąbrowska, A.M., Marquardt, M., Renner, A.H.H., Tatarek, A. & Reigstad, M. (2023). Seasonal patterns of vertical flux in the northwestern Barents Sea under Atlantic Water influence and sea-ice decline. <i>Progress in Oceanography, 219</i>, 103132. Also available in Munin at <a href=https://hdl.handle.net/10037/31551>https://hdl.handle.net/10037/31551</a>. <p>Paper III: Digernes, M.G., Bodur, Y.V., Amargant-Arumí, M., Hawkes, J.A., Kohler, S.G., Müller, O., Dietrich, U., Reigstad, M. & Paulsen, M.L. Contrasting seasonal patterns in particle aggregation and DOM transformation in a sub-Arctic fjord. (Manuscript).en_US
dc.rights.accessRightsembargoedAccessen_US
dc.rights.holderCopyright 2024 The Author(s)
dc.subject.courseIDDOKTOR-002
dc.subjectArctic shelvesen_US
dc.subjectArctic Oceanen_US
dc.subjectbenthosen_US
dc.subjectBarents Seaen_US
dc.subjectNortheast Greenlanden_US
dc.subjectfjorden_US
dc.subjectcarbon cycleen_US
dc.subjectcarbon exporten_US
dc.subjectparticulate organic matteren_US
dc.titleAspects of the biological carbon pump in the Atlantic sector of the Arctic: Aggregation, vertical flux and pelagic-benthic couplingen_US
dc.typeDoctoral thesisen_US
dc.typeDoktorgradsavhandlingen_US


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