Phenotypic and transcriptional plasticity in alpine copepods

As part of the zooplankton community, copepods are a key component of aquatic food webs. In their natural habitat, these organisms are exposed to diverse stressors that vary among lakes and often show strong seasonal fluctuations. While many alpine lakes are clear, they turn turbid when fed by glacial meltwater carrying mineral particles, thus reducing damaging UV radiation, but also modifying the food basis for zooplankton. Copepods adjust to changing environmental conditions via long-term acclimatization (e.g., accumulation of photoprotective compounds), but also show short-term stress responses at the molecular level. However, the exact relationships between specific stressors and different defense strategies are still unknown. Changes in the expression of genes reflect the physiological condition of an organism, which can be quantified by molecular methods. Next- generation sequencing (RNA-seq) allows for quantitative assessment of gene expression, thus providing a snapshot of cellular processes. In this project, these novel approaches will be combined with modern physiological techniques to elucidate how glacier-derived turbidity affects copepods at the cellular level and whether stress responses and acclimatization strategies differ on spatial and temporal scales. For this purpose, we will sample a set of alpine lakes along a turbidity gradient, two of which (one clear and one turbid) will be visited regularly during the course of a year. In addition, experimental work will be done to separate the differential effects of turbidity and UV radiation on copepods. The project will contribute significantly to our understanding of the challenges faced by planktonic organisms in alpine lakes and the survival strategies they employ.