Thesis Investigating the circadian clock

Antarctic krill (Euphausia superba) is together with the pelagic tunicate S. thompsoni one of the dominant macrozooplankton grazer in the Southern Ocean (SO). Both species can form dense swarms and efficiently graze on phytoplankton in the upper water layer. Phytoplankton is packed into fast sinking fecal pellets, thereby both krill and salps contribute significantly to the carbon sequestration in the SO via the biological carbon pump (BCP). A significant behavioral trait of krill and salps is diel vertical migration (DVM), known as a rising from the depth at dusk for feeding and returning to deeper and darker layers at dawn to avoid visually hunting predators. Recent studies suggest that DVM of zooplankton species strongly increases the efficiency of carbon transport to the deep. While the underlying reason for DVM seems obvious, little is known about the direct driver of this behavior. Studies on the krill biological clock suggest that krill DVM is underpinned by an endogenous rhythm that allows to anticipate the daily rhythm of day and night, thus optimally balancing the trait off between feeding and predator avoidance. Further work on krill has shown that the biological clock is also involved in the temporal orchestration of several daily and seasonal metabolic functions of krill. However, currently, nothing is known about the biological clock and the architecture of its molecular mechanism in S. thompsoni.

In face of climate change, the Western Antarctic Peninsula (WAP) is one of the most rapidly warming regions worldwide. Here, the climatic changes have led to a southward shift of krill and an increase in salp abundance around the WAP. A new study by Pauli et al. (2021) suggests that the interaction between krill and salps at the WAP may have strong effects on the carbon export efficiency. However, further studies on the behavioral characteristics in both species (e.g. DVM) is needed to better understand these interactions. This study investigates for the first time the potential presence of an endogenous clock in S. thompsoni. These results will be compared with the molecular clock machinery in E. superba to increase our understanding of the underlying mechanisms of krill and salp daily rhythms, potential effects on their interaction and ecosystem functioning.

Tasks

During a cruise with the research icebreaker Polarstern in 2018 (PS112), 24- hour samplingsof krill and salps were performed around Elephant Island in the Southern Ocean. As part of this project, relative mRNA expression levels of the core clock genes of krill and salps will beinvestigated using quantitative real-time PCR (qPCR). The expression of the clock genes will be investigated for their pattern and rhythms of expression in relation to diel cycles in e.g. light intensity.

Requirements

• Master student with background in biology, ecology, molecular biology, environmental science
• Molecular biological skills (quantitative real-time PCR)
• General interest in Southern Ocean and marine ecology

Further Information

• Start of the project: September 2022
• The work will take place in the working group “Ecophysiology of pelagic key species” of Prof. Bettina Meyer at the Alfred-Wegener Institute (AWI)
• Working place will be mainly the AWI in Bremerhaven

You are interested?

Please send your application (including a brief statement of your research interests and relevant skills) via email to
and
Literature: Pauli, N. C., C. M. Flintrop, C. Konrad, E. A. Pakhomov, S. Swoboda, F. Koch, X. L. Wang, J. C. Zhang, A. S. Brierley, M. Bernasconi, B. Meyer and M. H. Iversen (2021). "Krill and salp faecal pellets contribute equally to the carbon flux at the Antarctic Peninsula." Nat Commun 12(1): 7168

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