Intraspecific differences in metabolic rates shape carbon stable isotope trophic discrimination factors of muscle tissue in the common teleost Eurasian perch ().

Stable isotopes represent a unique approach to provide insights into the ecology of organisms. δC and δN have specifically been used to obtain information on the trophic ecology and food-web interactions. Trophic discrimination factors (TDF, ΔC and ΔN) describe the isotopic fractionation occurring from diet to consumer tissue, and these factors are critical for obtaining precise estimates within any application of δC and δN values.

Fatty acid accumulation in feeding types of a natural freshwater fish population.

Fatty acids are widely used to study trophic interactions in food web assemblages. Generally, it is assumed that there is a very small modification of fatty acids from one trophic step to another, making them suitable as trophic biomarkers. However, recent literature provides evidence that many fishes possess genes encoding enzymes with a role in bioconversion, thus the capability for bioconversion might be more widespread than previously assumed.

Short-term apparent mutualism drives responses of aquatic prey to increasing productivity.

According to apparent competition theory, sharing a predator should cause indirect interactions among prey that can affect the structure and the dynamics of natural communities. Though shifts in prey dominance and predator resource use along environmental gradients are rather common, empirical evidence on the role of indirect prey-prey interactions through shared predation particularly with increasing productivity, is still scarce. In an 8-week lake mesocosm experiment, we manipulated both the addition of inorganic nutrients and the presence of generalist fish predators (crucian carp, Carassius carassius L.

The CO -equivalent balance of freshwater ecosystems is non-linearly related to productivity.

Eutrophication of fresh waters results in increased CO uptake by primary production, but at the same time increased emissions of CH to the atmosphere. Given the contrasting effects of CO uptake and CH release, the net effect of eutrophication on the CO -equivalent balance of fresh waters is not clear. We measured carbon fluxes (CO and CH diffusion, CH ebullition) and CH oxidation in 20 freshwater mesocosms with 10 different nutrient concentrations (total phosphorus range: mesotrophic 39 µg/L until hypereutrophic 939 µg/L) and planktivorous fish in half of them.

Climate warming and heat waves alter harmful cyanobacterial blooms along the benthic-pelagic interface.

In addition to a rise in mean air and water temperatures, more frequent and intense extreme climate events (such as heat waves) have been recorded around the globe during the past decades. These environmental changes are projected to intensify further in the future, and we still know little about how they will affect ecological processes driving harmful cyanobacterial bloom formation. Therefore, we conducted a long-term experiment in 400-L shallow freshwater mesocosms, where we evaluated the effects of a constant +4°C increase in mean water temperatures and compared it with a fluctuating warming scenario ranging from 0 to +8°C (i.

Life-history traits buffer against heat wave effects on predator-prey dynamics in zooplankton.

In addition to an increase in mean temperature, extreme climatic events, such as heat waves, are predicted to increase in frequency and intensity with climate change, which are likely to affect organism interactions, seasonal succession, and resting stage recruitment patterns in terrestrial as well as in aquatic ecosystems. For example, freshwater zooplankton with different life-history strategies, such as sexual or parthenogenetic reproduction, may respond differently to increased mean temperatures and rapid temperature fluctuations. Therefore, we conducted a long-term (18 months) mesocosm experiment where we evaluated the effects of increased mean temperature (4°C) and an identical energy input but delivered through temperature fluctuations, i.