Statement regarding the COVID-19 situation: The implementation of the project TPOINT has been affected by the ongoing COVID-19 pandemic at various levels (research, training of the researcher, dissemination and communication of project results). Nevertheless, major milestones and objectives of the project could be achieved with some deviations. Open objectives will be finalized in the near future (see project website below for future updates).
Overview of work performed in the project:
Objective 1: Analyse and quantify the direct impacts of trematodes and temperature on blue mussels.
In Objective 1, we performed a large-scale mesocosm study analysing the direct effects of trematode infections and temperature on blue mussels Mytilus edulis. In the experiment, experimental mussel beds were exposed to the trematode species Himasthla elongata individually, a combination of the trematode species Himasthla elongata and Renicola roscovita, or no parasites in control groups. To assess the impacts of climate change-induced temperature increases, each set of mesocosms was tested under three temperature scenarios, 17, 20 and 23°C.
The mesocosm experiment was conducted as planned. However, sample processing and analysis were delayed due to COVID-19 lockdown restrictions and limited laboratory access for prolonged periods. At the time of reporting, data analysis and preparation of the manuscript are ongoing. Preliminary data suggest a strong impact of temperature on the parasite infection intensity in blue mussels, which supports our initial hypothesis.
Objective 2: Assess the indirect effects of parasitism and temperature on mussel predation, mussel bed structure and the role of mussel beds as secondary habitat for other organisms (facilitation).
In Objective 2, we conducted a field experiment testing the effects of parasitism and temperature on M. edulis predation, mussel bed structure and the mussels’ role as secondary habitat. The experiment consisted of four treatments: parasitized mussels/open cage, parasitized mussels/closed cage, unparasitized mussels/open cage, and unparasitized mussels/closed cage. While open cages allowed exposure of mussels to predators, closed cages prevented predation but allowed recruitment and colonisation of other organisms to the mussel beds. All cages were deployed at Kalø Vig (56°16'52.5"N 10°29'07.0"E) for 8 months (October 2020 –June 2021) to allow predation and mussel bed recruitment to occur during the spring and early summer months. After the experiment, cages and epifauna were recovered and the mussel bed structure and associated plant and animal communities assessed.
The experiment could be conducted as planned but preparation and deployment of the cages were delayed due to COVID-19 lockdown restrictions. All samples have been retrieved from the field site and sample processing is ongoing at the time of reporting.
Objective 3: Develop a prediction model of the dynamics of blue mussel populations under the pressures of parasites and climate change
In Objective 3, we are currently developing an individual-based model (IBM) that tracks mussel dynamics (i.e. abundance and population structure) under varying scenarios of climate change and parasite pressure. The blue mussel IBM tracks M. edulis individuals in a population, as they grow, develop, obtain parasites, and die (including predation). Interactions between biology and the environment (temperature and parasites) are parameterized via the results of objectives 1 and 2, existing literature data, along with physical (e.g. temperature) predictions for the future northeast Atlantic. Model output will predict future blue mussel dynamics (abundance, population structure) as well as the underlying physiological rates under different climate change and parasite infection scenarios. The IBM allows us to simulate if and under which conditions blue mussel populations could reach a critical tipping point.
Design and implementation of the IBM have been delayed due to interruptions in previous objectives that provide the basis for the model. Completion of the model is expected once data from objectives 1 and 2 are available.
Although not all work packages and objectives could be completed at the time of reporting, available results and data indicates that TPOINT provides excellent results to significantly advance our understanding of how environmental changes have intricate and cascading effects on complex host-parasite systems in marine environments. Please visit the TPOINT website for future updates on the project and publications:
https://selbach.weebly.com/tpoint-project.html(s’ouvre dans une nouvelle fenêtre)
