Phd students

Satish Pawar

Habitat suitability and potential recovery of eelgrass.

Karen Timmermann and Jens Kjerulf Petersen, DTU Aqua

Eelgrass is one of the common aquatic vegetation in the northern temperate coastal regions. It provides valuable ecosystem services like nursery grounds to juvenile fish, improve water quality and sequester carbon as green biomass. The eelgrass meadows in Danish coastal waters were damaged due to stone fishing and frequent eutrophication episodes. These activities have been discontinued and water quality has improved over the last decade. However, the eelgrass has not recolonized the previously occupied habitat sites. Understanding the factors affecting eelgrass recovery is primary task in eelgrass habitat restoration and future management.

The eelgrass growth could be affected from local disturbances along with global phenomena of climate change. This project aims to understand the combined effect of these factors affecting eelgrass recovery. This will be achieved by combining the monitoring data of eelgrass environment and habitat suitability modelling techniques. Continuous satellite data will provide spatial habitat variables like light availability, turbidity and Sea Surface Temperature (SST) of shallow waters. The habitat suitability analysis will be performed by implementing the eelgrass growth model with spatial habitat data along with correlation-based niche models to spatially map potential habitats. The growth models can simulate climate change scenarios to evaluate effect of eutrophication and increased water temperature.

Combining satellite data and modeling will provide new knowledge on shallow water environment in Danish coastal waters. The project will contribute significant insight into the combined effect of eutrophication and climate change on eelgrass health. From the spatial outputs of habitat suitability, eelgrass zones for potential recovery can be identified for their management. The information obtained from spatial simulations can aid in planning restoration activities and forming policies for eelgrass conservation.

Isabelle Johansson

Stability of subtidal blue mussel bed in coastal areas

Pernille Nielsen, Camille Saurel and Daniel Taylor, DTU Aqua

Blue mussels are an ecosystem engineering bivalve that enhances biodiversity by creating habitats for other species, contributes to a local particle reduction by controlling phytoplankton biomass and water clarification. Stability of blue mussel beds and factors influencing variation in populations between years is not always understood, especially in eutrophied subtidal areas. Limfjorden is the main area for both blue mussel fishery and aquaculture in Denmark and the mussel stocks are surveyed annually. However, the current large-scale mapping is resource intensive. 

This project aims to understand factors influencing development and stability of mussel bed in subtidal areas. This will be achieved by performing survival analysis on temporal mussel beds using a time series of stock assessment data, black box data from fishing vessels and environmental data. Furthermore, production efficiency for wild mussel seeds in on-bottom culture in Limfjorden will be explored, to find the optimized density of mussels to relay in culture plots. Finally side scan sonar imagery collected for various mussel beds (wild, culture plots and restored beds) will be investigate regarding the possibilities to develop automated data processing methods to optimize the mapping of areal distribution, coverage, and biomass of mussel beds. 

This project is expected to assess the stability and document factors affecting the stability of mussel beds in eutrophic subtidal areas. The outputs will contribute to the sustainable development of mussel production and can improve management of biogenic habitats as well as fisheries/aquaculture management. During this project existing non-invasive techniques will be optimized and developed to map areal distribution, densities, and biomass of blue mussel beds. The methodology could be applied for multiple purposes benefitting fishery management by improve methods for stock assessments, optimizing the cultivation practices of on-bottom mussel aquaculture or establishment and monitoring of restored mussel beds. 

Thiviya Nair

Disease-free production of European flat oysters

Camille Saurel and Lone Madsen, DTU Aqua

The Danish Limfjorden was once rich with European Flat Oysters (Ostrea edulis), treasured as a reef engineer and a nutritious source of protein by local and foreign markets. Unfortunately, the spread of the invasive micro-parasite, Bonamia ostreae, and overfishing for the flat oysters in Europe eventually caught up with the region, decimating their populations. In 2020, the Limfjorden lost its disease-free status and relies on the production of Bonamia-free spat to seed shellfish aquaculture and reef restoration efforts. Bonamia-free spat production relies on accurate and early detection of the parasite, as its life cycle outside of its host is unclear, and infections are often diagnosed when it is too late.

My projects will aim to investigate the biotic and abiotic factors that contribute to the activation of bonamiosis in flat oysters and potential treatments that can be applied to limit B. ostreae’s infectivity. The project will also include testing early and non-destructive sampling methods for parasite detection and provide a basis for biosecurity protocols required for successful Bonamia-free oyster spat production in the Danish Shellfish Centre hatchery at Nykøbing Mors.

The discoveries that will be made in this project will fill up the knowledge gaps on the life cycle and behaviour of B. ostreae. The disease testing methods refined in this project will also serve as a potential early alarm system for hatcheries and Bonamia-free sites. Developments from this project will enable shellfish farm managers to formulate the best mitigation strategies and avoid financial losses. The Bonamia-free spat produced through the efforts of this project can go on to seed future reefs and fisheries, thereby reviving the flat oyster populations in the Limfjorden.

Ana Lilia Tovar Aguirre

Title of PhD project
Microalgae production for shellfish hatchery

Supervisors
Camille Saurel, DTU Aqua and Marie Renaudie, Nantes University

Background of the project
Aquaculture, a rapidly growing sector of food production, is crucial for meeting the global demand for seafood. The European flat oyster (Ostrea edulis) is of significant ecological and economic importance. A critical factor in the success of oyster hatcheries is the quality of microalgal feed, which must meet the nutritional needs of oysters at various life stages. While monocultures of microalgae have been the traditional choice, studies highlight the advantages of using mixed microalgae cultures. Native, local, undefined poly microalgae cultures may offer cost-effectiveness, and high-quality nutritional profiles, making them a promising alternative for sustainable oyster farming.

About the project
This PhD project focuses on using local, undefined poly microalgal cultures as a sustainable and effective feed source for Ostrea edulis in hatcheries. The research will explore the potential of these natural microalgal communities by adapting them to controlled hatchery environments. By examining different factors, the project aims to optimize the cultivation of these polycultures to enhance their suitability as oyster feed. Additionally, the study will investigate the scalability of these cultures from lab-scale to larger production systems, assessing their impact on oyster growth, tissue composition, and overall health.

Perspectives
The findings from this project will advance sustainable aquaculture practices by demonstrating the viability of local, native, microalgal polycultures as a high-quality feed option for oyster hatcheries. This approach could lead to reduced feed costs and improved oyster productivity, contributing to the long-term sustainability of the aquaculture industry. Beyond aquaculture, the insights gained could have broader applications in different areas where polycultures could be suitable.

Previous PhD students within the research area Coastal Ecology

Development of drone-based tools for the monitoring of submerged aquatic vegetation

Restoration and non-invasive monitoring of geogenic reefs in temperate waters

Investigating hatchery and cultivation methods for improved cultivation of Palmaria palmata 

Mitigation culture of mussels: Production and ecological impacts

Helle Torp Christensen
Area-intensive bottom culture production of blue mussels, Mytilus edulis (L.)