PhD students

PhD students and projects at DTU Aqua within the research area Oceanography.

Magnus Heide Andreasen

Title of the PhD project
Global change and gelatinous zooplankton: Mechanisms and responses of jellyfish population dynamics to global change induced stressors

Supervisors
Torkel Gissel Nielsen & Mollie E. Brooks

Background of the project
Gelatinous zooplankton organisms are a diverse group of soft bodied, transparent organisms that comprise members from diverse phyla in the animal tree of life. They commonly attract large public attention partly due to their bloom and bust population dynamics, partly due to their interference with human activities especially in coastal waters. It has been suggested that their abundances are on a rise due to global change induced stressors. However, the data and experimental basis to support this hypothesis remains inconclusive.

About the project
The aim of this PhD project is to address the hypothesis that gelatinous zooplankton biomass is increasing due to global change induced stressors from a time series as well as experimental perspective. The project will combine statistical modelling with laboratory-controlled experiments.

Perspectives
The results are expected to further our understanding about gelatinous zooplankton’s long-term abundance fluctuations, their underlying population dynamics and the response of certain sub-populations to global change induced stressors.

Federica Miano

Title of the PhD project
Fluid dynamics, ecology, and evolution of flagellate foraging

Supervisors
Thomas Kiørboe, Seyed Saeed Asadzadeh and Anders Andersen

Background of the project
Flagellates represent highly relevant species among eukaryotes both from evolutionary and ecological perspectives. They are found among all the branches of the eukaryotic tree of life, with highly diverse flagellar arrangements and resource acquisition modes. Also, they play a crucial role in the biogeochemical cycles of the global ocean. Their key position in the microbial food web is governed by their feeding on bacteria and other picoplankton, by their photosynthetic activity, and by themselves being grazed by predators. Their degree of success in eating without being eaten is the key to understand the functioning of predatory flagellates. Their feeding activity dangerously ex-poses them to rheotactic predators that are sensitive to flow disturbances. Therefore, flagellates have evolutionarily developed singular behaviors in terms of feeding modes and predator avoidance, to find an equilibrium between resource acquisition and predation risk. These trade-offs are still largely unexplored among flagellates.

About the project
During my PhD, I will study representative flagellate species belonging to different branches of the eukaryotic tree of life to look at their behaviors both as predators and prey. Firstly, I will investigate escape responses from predators feeding currents to understand their propulsion mechanism that leads to very fast and long jumps, and characterize the fluid signals that elicit them. Secondly, I will quantitatively investigate the kinematics and 3-dimensional beat patterns of diverse flagellar arrangements and use them as input to CFD models to quantify foraging-predation risk trade-offs.

Perspectives
My PhD project aims at describing these trade-offs quantitatively and at understanding how they are differently optimized among flagellate species. This is crucial because the diversity of eukaryotic microbial communities is determined by such trade-offs in concert with environmental constraints and microbial diversity in turn governs the functionality and “services” of microbial communities and so their role in ocean biogeochemistry.

Caroline Gjelstrup

Title of the PhD project
Changing oceanographic conditions of East Greenland and its link to regional fisheries

Supervisors
Colin Stedmon, André Visser and Jesper Boje

Background of the project
Knowledge of oceanographic conditions and their variability is essential for assessment of environmental impacts on biological communities, ecosystem services and regional climate variability. East Greenland is a region of both climatic and ecological importance, providing a connection between the Arctic and Atlantic oceans as well as eco-system services such as carbon sequestration and fisheries production. The region is influenced by cold fresh waters from the Arctic and warm saline waters from the Atlantic divided by a continuous front extending along the shelf-break. Oceanographic fronts are often associated with elevated plankton production due to entrainment of nutrients enhancing phytoplankton growth and zooplankton grazing, which supports pelagic and demersal fish. Ongoing Arctic climate change, including diminishing sea-ice cover, increasing discharge from the Greenland ice sheet and anomalous warm water pulses of subtropical origin propagating through the region, alter the physical environment.

About the project
This PhD project aims to improve our understanding of variability in oceanographic conditions in East Greenland, and how this relates to ecosystem change and fisheries productivity. A combination of in-situ and remotely sensed observational data will be used to characterize oceanographic conditions and resolve underlying mechanisms responsible for variability herein. Eventually, a trait-based model will be applied to understand how changes in environmental conditions influence ecosystem function.

Perspectives
By gaining insights as to how the spatiotemporal distribution of water masses in the East Greenland region are changing, and what that change implies for nutrient availability and plankton dynamics we can begin to foresee how East Greenland will respond to future change.

Athanasios Kandylas

Title of the PhD project
Carbon sequestration and oxygen minimum zones

Supervisor
Andre Visser & Ken H. Andersen

Background of the project
Oceans play a crucial role in regulating and stabilizing the Earth’s climate having stored nearly 40% of the anthropogenic CO₂ emissions since the industrial revolution. However, potential tipping points might lead to abrupt changes of critical physical and biological processes affecting important marine ecosystem services, such as carbon sequestration and food production. Even though the science around the physics of climate change is robust, our understanding about the response of the marine ecosystems to these changes is still incomplete.

About the project
The aim of this PhD is to develop a framework through advanced ecological modelling which will be able to give an insight into the ecological state of the majority of the marine ecosystems around the world. We expect that at the end of this process, we will have gained a better understanding of two important and interrelated phenomena: Carbon Sequestration and Oxygen Minimum Zones (OMZ) in the ocean. To accomplish this, the Nutrient – Unicellular – Multicellular (NUM) framework and the SISSOMA, a specialized aggregation model, developed in the Centre for Ocean Life will be applied.

Perspectives
Overall, in a fast-changing world we need to be able to make accurate predictions about the function and structure of marine ecosystems on a global scale. The tools developed in this project work on this direction and they will hopefully help us to take critical management decisions on time.

PhD projects at DTU Aqua

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PhD study at DTU

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