Understanding aquatic Herbivore performance under changing regimes of thermal and nutritional Variance (HerbiVar)
Final Report Abstract
Altered thermal regimes and changes in nutrient supply are among the most prominent drivers of global change. Recent studies predict important changes to the frequency, intensity and duration of climate extremes, which will manifest in the higher statistical moments (e.g. variance and skewenness) of temperature spatial and temporal frequency distributions. The mean properties and likely the spatio-temporal variance of the food resources (in terms of energy, biochemical and mineral composition) available to the ectotherms are also affected. Temperature dictates the energy acquisition and expenditure in ectotherms but also their structural requirements for specific nutrients. Hence, the concomitant changes of temperature and resource quality have to be considered simultaneously in any attempt to understand of ongoing and future changes of ectotherm populations. The ambition of this project was to improve our understanding of how food quality-temperature interactions manifest in a dynamic environment in which one or both factors fluctuate within the lifetimes of individuals. The project generated experimentally response surfaces of the main fitness components (development, reproduction, survival) of the model organism Daphnia magna to temperature and algal resource quality (in terms of essential fatty-acids, cholesterol and phosphorous supply). We further demonstrated the importance of cholesterol and phosphorus supply into modulating thermal tolerance in Daphnia magna and therefore its capacity to withstand extreme heat episodes. We allocated an important effort into the development of a theoretical framework that can be used to predict the performance of ectotherms in a dynamic environment with multiple fluctuating co-limiting factors (here, resource quality and temperature) from “static” response surfaces. Using Dynamic Energy Budget models, we further explored how the capacity to acclimate to resource quality and to store limiting nutrients when abundant can influence consumer performance in dynamic environments. Finally, the theory developed in the project was used to predict and explain how thermal variability (here, diurnal fluctuations) affected the maximum intrinsic growth rate rmax of a phytoplankton communities in different nutritional contexts (Phosphorus and Nitrogen supply rate and ratio).
Publications
- (2017). Understanding and predicting individual performance in fluctuating and multifactorial environments (Concepts & Synthesis). Ecological Monographs 87(2): 178-197
Koussoroplis AM, Pincebourde S, Wacker A
(See online at https://doi.org/10.1002/ecm.1247) - (2019) Feeding in the frequency domain: coarser-grained environments increase consumer sensitivity to resource variability, covariance and phase. Ecology letters 22(7):1104-1114
Koussoroplis AM, Schälicke S, Raatz M, Bach M, Wacker A
(See online at https://doi.org/10.1111/ele.13267) - (2019) Phytoplankton community responses to temperature fluctuations under different nutrient concentrations and stoichiometry. Ecology 100 (11): e02834
Gerhard M, Koussoroplis AM, Hillebrand H, Striebel M
(See online at https://doi.org/10.1002/ecy.2834)
