Deglaciation in mountain catchments changes water source contributions and associated habitat conditions in usually cold and dynamic mountain rivers. Although recent research has listed consequences of glacier retreat for aquatic biodiversity, specific invertebrate and algal groups, quantitative effects on the aquatic food web structure remain poorly understood. In this study we assessed abiotic habitat conditions together with the composition and the biomass of periphyton in 5 catchments in the Central European Alps over the snow-free period and reveal significant links to declining glacier cover. We found that reduced glaciation leads to decreasing sediment concentrations and also to lower runoff, which in combination affects the stability of benthic habitats. The reduced sediment load of the rivers dominates the consequences of glacial retreat in subsequent river habitats more than the decreasing nutrient supply. Periphyton biomass in glacier-fed rivers is expected to increase with ongoing deglaciation and warming, which subsequently favors particularly diatoms and cyanobacteria. This work thus illustrates clear links between decreasing glacier cover and the identity and relevance of aquatic producers in alpine river catchments, and provides evidence for shifting resource base in terms of biomass with potential consequences for its nutritional quality.

As lakes receive and transform significant amounts of terrestrial carbon, they often act as source of atmospheric CO2. Yet, long-term measurements of lake-atmosphere CO2 exchange with high temporal resolution are sparse. In this study, we measured the CO2 exchange of a small lake situated in complex mountainous topography in the Austrian Alps continuously for one year. We used the eddy covariance (EC) and the boundary layer model (BLM) approaches to estimate the lake’s CO2 source or sink strength and to analyze differences between these methods. Overall, CO2 fluxes were small and EC measurements indicated influence of low-frequency contributions. Results from both the EC and the BLM methods indicated the lake to be a small source of atmospheric CO2 with highest emissions in fall. During night-time, the CO2 concentration gradient at the air-water interface decreased due to an increase in atmospheric CO2 above the lake, likely caused by cold and CO2-rich air draining from the surrounding land. Consequently, BLM fluxes were lower during night-time than during daytime. This diel pattern was lacking in the EC flux measurements because the EC instruments deployed at the shore of the lake did not capture low nocturnal lake CO2 fluxes due to the local wind regime. Overall, this study exemplifies the relevance of the surrounding landscape for lake-atmosphere flux measurements. We conclude that estimating CO2 evasion from lakes situated in complex topography needs to explicitly account for biases in EC flux measurements caused by low-frequency contributions and local wind systems.

The nutritional diversity of resources can affect the adaptive evolution of consumer metabolism and consumer diversification. Omega-3 long-chain polyunsaturated fatty acids (n-3 LC-PUFA) have a high potential to affect consumer fitness, through their widespread effects on reproduction, growth, and survival. However, few studies consider the evolution of fatty acid metabolism within an ecological context. In this review, we first document the extensive diversity in both primary producer and consumer n-3 LC-PUFA distributions among major ecosystems, between habitats, and among species within habitats. We highlight some of the key nutritional contrasts that can shape behavioral and/or metabolic adaptation in consumers, discussing how consumers can evolve in response to the spatial, seasonal, and community-level variation of resource quality. We propose a hierarchical trait-based approach for studying the evolution of consumers’ metabolic networks, and review the evolutionary genetic mechanisms underpinning consumer adaptation to n-3 LC-PUFA distributions. In doing so, we consider how the metabolic traits of consumers are hierarchically structured, from cell membrane function to maternal investment, and have strongly environment-dependent expression. Finally, we conclude with an outlook on how studying the metabolic adaptation of consumers within the context of nutritional landscapes can open up new opportunities for understanding evolutionary diversification.