PhD Theses at SCIENCE – University of Copenhagen

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Flocs in Focus: How Imagery and Dynamics of Suspended Particles Unravel Land-Sea Links

Publication: ResearchPh.D. thesis

Thor Nygaard Markussen

Suspended particle dynamics are important drivers for land-sea interactions. This has been examined in two coastal/marine environments, influenced by recently eroded particles from land. The main study region is an Arctic fjord, Disko Fjord on West Greenland. The rates of warming due to climate change are and will be particularly pronounced in the Arctic. This will increase glacial melt and permafrost thaw and increased amounts of nutrients, particles and other substances are expected to be mobilized. The presented study shows how labile iron interacts with suspended, primarily inorganic, particles in the fjord. We demonstrate that particle aggregation, flocculation, does not only enhance deposition near the source, but may also increase horizontal fluxes of particles rich in labile iron. In another study from the tropical Atlantic, we examine the interaction between inorganic particles, organic particles, and zooplankton. The study shows that the suspended particle dynamics are highly influenced by zooplankton grazing, and at the same time are influenced by the supply of inorganic particles from land, and we highlight that the interaction can have a large impact on the vertical flux of particles and carbon. The studies have used a recently developed camera system and demonstrate how micrometer imagery gives new and important information about the particle dynamics. The general assumption of flocculation always causing increased deposition is challenged. Chemical and biological reaction dynamics are shown to be fast, having the potential for significant alterations of fluxes over a short time. The potentially increased transport of labile iron, due to flocculation, can be of large relevance in polar regions under a changing climate, as more nutrients and particles may become available to coastal and marine ecosystems. Additionally, inorganic particle interactions with biological particles are likely to increase export of carbon to the deep ocean. Thus, there is a continued need for interdisciplinary thinking and study design to comprehend the suspended particle dynamics, and their relevance for earth system interactions.
Original languageEnglish
PublisherDepartment of Geosciences and Natural Resource Management, Faculty of Science, University of Copenhagen
Number of pages159
StatePublished - 2016

ID: 164159723