PhD projects within the research area Aquaculture.
Wanhe Qi
Title of PhD project
Water disinfection and biofilm activity in recirculating aquaculture systems (RAS)
Supervisors
Lars-Flemming Pedersen, Peter Vilhelm Skov & Kim Joao de Jesus Gregersen
Background of project
Recirculating aquaculture systems (RAS) have a high degree of water reuse, reduce environmental impacts and provide controlled rearing conditions for fish production. All RAS rely on a central biological treatment process – biofiltration. This microbial process involves nitrifying bacteria that converts toxic ammonium (excreted from the fish) to harmless nitrate. It is crucial to get more information about how water disinfection strategies affect biofilter performance. Currently, such assessment is difficult to perform, and there is limited knowledge and tools available to understand and quantify the mechanisms, activity and importance of surface attached bacteria known as biofilm.
About the project
The PhD project is supported by a joint Danish-Norwegian research project “RASHealth” (nofima.no/en/project/rashealth), where assessment of disinfection strategies on water quality and biofilm activity is central. The aim of my PhD project is to develop simple, fast and practical assays to quantify biofilm activity that can be used as a tool to assess biofilter performance, disinfection efficacy and predict disinfection demand in RAS.
Perspective
The outcome from my research will provide tools to test biofilm activity under controlled lab-scale experimental conditions and pilot-scale practical situations. This will provide guidelines for improved disinfection strategies in RAS and generate theoretical and applied knowledge on biofilm formation and tolerance during disinfection practice. Ultimately, these efforts will support ongoing research and development of biofilter designs and RAS operation.
Alexandre Nguyen-tiêt
Title of PhD project
Characterization of H2S producers in Recirculating Aquaculture Systems (RAS)
Supervisors
Sanni-Leea Hellevi Aalto, Lars-Flemming Pedersen & Stefan Bertilsson
Background of project
Hydrogen sulfide (H2S) is an extremely toxic compound for organisms, preventing aerobic respiration. In marine land-based recirculating aquaculture systems (RAS), H2S production is a major challenge, leading to fish mortality and thus important economic consequences. Because of the high sulfate (SO42-) and organic matter concentration present in marine RAS, H2S production has been associated with the sulfate-reducing bacteria (SRB). However, there are also other pathways for producing H2S that could play a significant role but are currently neglected, e.g. some bacteria have the capacity to degrade the cysteine to produce pyruvate, ammonia and H2S. In both marine and freshwater RAS, cysteine is present, originating from the uneaten feed and feces of fish, suggesting that cysteine degradation could be an important H2S source in aquaculture environment.
About the project
The main goal of this PhD project is to gain knowledge on the bacterial communities responsible of H2S production in RAS and especially the cysteine degrading bacteria. To do so, I will first enrich and cultivate H2S producing bacteria from samples collected at several locations in RAS. After that, I will use metagenomic/metatranscriptomic analysis to identify the bacteria as well as the metabolic pathways responsible of H2S production and develop primers to examine H2S production dynamics and microbiology in aquaculture biofilms.
Perspective
The results obtained through this project will give a better understanding of the microbial community responsible of H2S production in land-based aquaculture. With this new knowledge, I can develop ways to quantify and monitor both the traditional (SRB) and cysteine-degradation H2S producers in RAS to avoid production losses related to H2S exposure and to promote safe and stable fish production in the future.
Previous PhD students (since 2020)
Xiaoyu Huang
Effects of feed on water quality in recirculating aquaculture systems
(link awaits publication of thesis)
Julie Hansen Bergstedt
Hydrogen sulfide in marine recirculating aquaculture systems and the effects of hydrogen sulfide exposure on the metabolism, welfare, and production performance of Atlantic salmon (Salmo salar)
(link awaits publication of thesis)
Kylian Manon Eggink
Modification of the nutritional composition of black soldier fly (Hermetia illucens) for fish feed applications
Go to DTU Orbit to download thesis
Freja Manø Busk Karlsen
Evaluation of chemical and biological refinement strategies for transforming brewer’s spent grain into a high-quality protein source for fish feed
Go to DTU Orbit to download thesis
Tilo Pfalzgraff
Effects of cortisol on the nutrient utilisation and bioenergetics of rainbow trout
Go to DTU Orbit to download thesis
Renata Goncalves
Ontogenetic development and nutritional requirements in early life stages of the European lobster (Homarus gammarus, L.)
Go to DTU Orbit to download thesis
Kim João de Jesus Gregersen
Beyond water quality: Micro particles in Recirculation Aquaculture Systems
Go to DTU Orbit to download thesis