PhD students within the research area Marine Populations and Ecosystem Dynamics
Amalia Papapostolou
Title of PhD project
Trophic efficiency of the pelagic food chain
Supervisors
Ken Haste Andersen, André Visser & Camila Serra-Pompei
Background of project
The structure of the marine food web plays a crucial role for fisheries and ocean biogeochemistry. Food webs consist of interconnected food chains and in the ocean a food chain typically follows the sequence: phytoplankton, herbivorous zooplankton, carnivorous zooplankton, upper trophic levels (i.e. forage fish). It can take a varying number of steps within a food chain for energy to transfer from phytoplankton to fish across different oceanic regions, depending on the planktonic community composition. The length of the food chain is tightly linked to the concept of “trophic efficiency”, namely the efficiency with which energy flows from one trophic level to the next through predation.
About the project
The aim of my PhD is to make global estimates of the ‘microbial’ trophic efficiency from phytoplankton to small pelagic fish; basically how does energy flow across the food chain. This is crucial to improve our estimates and predictions for fisheries yields and carbon export. To do so, I will explore the mechanisms that govern marine food web dynamics through trait-based modeling, by implementing and further developing the “NUM” model framework, created at the Center for Ocean Life. NUM is a mechanistic size- and trait-based model along the Nutrient-Unicellular-Multicellular axis, based on individual-level processes. In NUM, the multicellular component encompasses ontogeny and describes the population dynamics of key copepod groups, characterized by their adult size and feeding mode. The composition of the plankton community is an emergent property of the model, resulting from predation and competition.
Perspective
With this PhD, we expect to identify the main mechanisms linking higher trophic levels, such as fish, to primary producers, and see how trophic efficiency correlates to fisheries yields and carbon export.
Marcel Montanyès Solé
Title of PhD project
Marine fish diversity patterns, drivers and underlying processes: present status and predictions under climate change
Supervisors
Martin Lindegren & Ken Haste Andersen
Background pf PhD project
Marine ecosystems and the services they provide are nowadays threatened by several pressures such as climate change, overexploitation of species, habitat destruction, and invasion of alien species. These pressures are likely to negatively affect taxonomic and functional diversity of marine habitats. Failing to identify future biodiversity trends and thus, to tackle the necessary management and conservation actions, will most likely lead to important biodiversity losses.
About the project
This project aims to study the effects of climate change and other human activities (e.g., fishing) on the past, present and future distribution, composition, and diversity of marine fish communities throughout the North Atlantic and North-east Pacific oceans. To achieve this overall aim, we also need to better understand the underlying responses of species to drivers and to key the assembly processes that shape the taxonomic and functional structure and composition of communities at different spatio-temporal scales. We will use available data on marine fish species occurrences and traits and environmental variables to build models that will allow us to study the above-mentioned subjects.
Perspective
This project will improve our understanding on the relative importance of the assembly processes and human activities in defining the fish community. Moreover, the study of biodiversity patterns and drivers will allow us to better understand how they will be affected by climate change, so knowledge can be translated into effective management and conservation measures that seek to preserve biodiversity and hence, human well-being.
Toni Vivó Pons
Title of PhD project
Trends and projections in invasive ecology: how susceptible to invasion are our marine ecosystems
Supervisors
Martin Lindegren, Patrizio Mariani & Cornelia Jaspers
Background of PhD project
The spread of non-indigenous marine species has been increasing over the last decades, having severe effects on the functioning of recipient ecosystems as well as a socio-economic impact. Studying biological invasions from a trait-based approach is really interesting to start addressing interactions between introduced and native species from recipient communities, as the functional similarity between non-indigenous and native species coupled with the community assembly rules (environmentally or biologically filtered) play a major role on the invasion success. As a quick example, within an invasion scenario, a greater trait similarity could imply stronger competitive interactions between natives and invaders that could either difficult the invader establishment or be detrimental for native species.
About the project
As a starting point the functional similarity between native and non-native organisms will be assessed, observing if the patterns of similarity are conditioned by the spatial scale, environmental or biotic conditions. This will be done by applying novel techniques for species modeling, which could allow to observe how species are associated by their traits or given certain environmental conditions. Then, the potential consequences derived from the differences in functionality between natives and non-natives will be addressed for recipient communities, e.g. the displacement or enhancing of certain native species, changes in ecosystem functionality or naturalization of the non-indigenous species.
Perspective
The main goal of this project is to propose a trait-based framework to study and better understand how native and non-indigenous species interact and which consequences these interactions could have on recipient communities. The results obtained could be really useful to expand knowledge about biological invasions in marine environments, and then transferred to policy makers to enhance the conservation efforts towards ecosystems under a biological invasion or more susceptible to be invaded in the future.
Paco Rodriguez-Tress
Title of PhD project
Optimizing important small pelagic fish resources by using data from scientific & commercial vessels
Supervisors
Stefan Neuenfeldt, Claus Reedtz Sparrevohn & Lise Laustsen
Background of PhD project
Schooling and swarming are dominant features in marine ecosystems and are observed in over 25% of bony fish species throughout their life. Despite being present through most of the commercial fish species, the fundamentals of schooling mechanisms, as for example triggers, are still not well understood to date. Thus, the distribution and the spatial structure of pelagic schools remains elusive, potentially controlled by a range of factors, that still remains to be elucidated. These small- and large-scale aggregation dynamics can lead to a mismatch between traditional surveys and fish distribution, and to predictable variability in occurrence and density of schools, which are important elements of the commercial cruise planning, fuel optimization and target decision.
About the project
Using direct commercial fishing data and underwater acoustic observations, this industrial PhD project will provide insight into the spatial distribution and schooling mechanisms of pelagic fishes. Going further in-depth with understanding causes of uncertainty in biomass estimates, it investigates the behavioural mechanisms of schooling fish during school-formation and -deformation at dusk and dawn. This way, spatial structure is understood as an emerging and predictable property of individual behavior and can be separated from measurement uncertainty.
Perspective
Small pelagic schooling fish are a sustainable and healthy protein source, which plays a key role in food security. They also have a significant potential for the green transition, as they are a CO2-friendly protein source. Conversely, the challenge when mobilizing fish in the green transition is to ensure sustainability and to maintain a low CO2 emission in the catching process. Thus, this project will provide mechanistic knowledge about spatial distribution of fish, so that stock assessments can be improved, and fishing optimized.
Costanza Cappelli
Title of PhD project
Physical processes affecting stock dynamics of blue whiting in the northeast Atlantic Ocean
Supervisors
Brian MacKenzie, Andre W. Visser & Hjálmar Hátún
Background of PhD project
Blue whiting (Micromesistius poutassou) is a mesopelagic gadoid species widely distributed in the northeast Atlantic Ocean, and it is commercially exploited throughout much of the region. It is both an important prey for many higher trophic level species and a zooplanktivore exerting significant top-down pressures. In the last 15 years, blue whiting has experienced considerable swings in abundance and recruitment. Despite its commercial and ecological importance, little is known about blue whiting stock dynamics in relation to atmosphere-ocean variability, constituting a major source of uncertainty for the management of this species.
About the project
In this PhD project, I will examine how large-scale changes in the ocean-climate conditions affect blue whiting recruitment and distribution in the North Atlantic Ridge area. Using statistical tools and agent-based particle tracking modelling approaches, I will provide a quantitative analysis of the relationship between large-scale oceanographic features in the North East Atlantic (e.g., subpolar gyre dynamics, wind stress curl) and the early life history of blue whiting (larval drift patterns, growth, and survival rates).
Perspective of project
This project will assess factors shaping temporal and spatial dynamics of blue whiting populations in relation to variable marine climate conditions in the North East Atlantic Ocean. The purpose is to develop models to understand the reproductive variability of blue whiting, as well as to improve stock assessments and fishery-related forecasts for this species. This knowledge will contribute to new ecosystem-based approaches to the management of blue whiting, UN Sustainability Development Goals related to Life Below Water, and an increased understanding of how climate change might impact productivity and biomass of this species.
Thøger Engelund Knudsen
Title of PhD project
Fish migration and ecosystem processes
Supervisors
Brian MacKenzie, Patrizio Mariani & Uffe H. Thygesen
Background of PhD project
Seasonal migration can serve as a strong advantage for many species across large scales of the animal kingdom. The Atlantic bluefin tuna is one such species, and travels vast distances, presumably in search for abundant prey resources. This tuna is of special interest in Denmark, as parts of its population have recently started consistently making the journey from the Mediterranean all the way to Skagerrak and Øresund.
About the project
The general objective of this PhD project is to create one or more models that are able to mathematically describe the existence and evolution of migratory routes in pelagic fish populations. It is possible to mathematically show how migration and its benefits can manifest in the evolution of a species due to natural selection. An individual will to an extent remember successful journeys it has undergone during its lifetime. However, it is poorly understood how this knowledge accumulates and persist, transcending through generations, especially for species without means of explicitly communicating this information. I seek to develop a novel framework that explains the existence and creation of migratory routes in social memory so that we can understand the spatio-temporal dynamics of populations of fish like the Atlantic bluefin tuna.
Perspective of the project
This project will help determine the key aspects for local populations of Atlantic bluefin tuna, hopefully ensuring that they have come to stay. Furthermore, the existence of a framework that describes the creation of migratory routes through collective behaviour will advance our ability to understand and predict changes in migrational patterns in a changing world.
Previous PhD students (since 2000)
Louise C. Flensborg
Resilience and vulnerability of marine fish communities to change
Go to DTU Orbit to download thesis
Regitze Benedicte Carlstedt Lundgreen
Spatial and temporal dynamics of movements in eastern Atlantic cod
Go to DTU Orbit to download thesis
Christian Kiær
Fish stock recruitment and marine ecological prediction
Go to DTU Orbit to download thesis
Kjetil Gjeitsund Thorvaldsen
Population ecology of mesopelagic fishesGo to DTU Orbit to download thesis
Rémy Denéchère
Metabolism, pace of life, and the dynamics of size-structured populations and communities. The case of fast-living squid
Go to DTU Orbit to download thesis
Peter Fink-Jensen
Stock structure and connectivity of capelin (Mallotus villosus) in Greenland: Otolith microchemistry used to track past whereabouts of a small, pelagic fish
Go to DTU Orbit to download thesis
Camila Serra Pompei
Trait-based models of plankton communities: from individuals to ecosystem functions
Go to DTU Orbit to download thesis
Neil Maginnis
The biogeography of Scleractinian reef corals: evidence from beta diversity
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Aurore Maureaud
Biodiversity-ecosystem functioning relationships in marine communities, Evidence from large-scale observations and modeling
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Trondúr Jónsson Kragesteen
Lice Management in Salmon Aquaculture, Using the Faroe Islands as a case site
Go to DTU Orbit to download thesis