How does pollution change the tolerance of warming conditions in Daphnia galeata?

Details

Supervisors

Dennis, Alice ; Willot, Quentin

Faculty

Faculté des sciences

Degree label

Master [120] en biologie des organismes et écologie, à finalité approfondie

Abstract

enClimate warming and eutrophication are major stressors for freshwater habitats. To understand how these two factors influence the primary consumer, five Daphnia galeata lineages were retrieved from the sediments of Swiss Lake Greifensee using resurrection ecology. Those five lineages were raised in low and high phosphorus conditions and exposed to six static temperatures to assess how the phosphorus condition impacted their temperature tolerance. The lineages were also compared with each other to see if their tolerance was impacted by historical conditions. Temperature tolerance was assessed using the Thermal-Death-Time (TDT) modelling, which allows for modeling the temperature-exposure duration relationship and avoids the limitations of Critical Thermal maximum (CTmax). In addition, several parameters can be obtained from the TDT, such as the thermal sensitivity (z), dynamic Critical Thermal maximums, and predicted critical temperature for a given long-exposure duration (Tc). We observed a strong impact of temperature on knockdown time, while phosphorus treatments had no significant effect on the heat tolerance of the five lineages. Lineages from the cooler historical period showed a lower heat tolerance, which was confirmed by the calculated dCTmax and Tc. Our results highlight how D. galeata may adapt to slow changes in temperature but may be at risk with longer extreme thermal events, such as heatwaves.