Phytoplankton are primary producers in freshwater ecosystems, forming the base of trophic networks. Some groups, such as cyanobacteria, have toxic potential, and their proliferation may be intensified by climate change, particularly warming, with significant impacts on aquatic food webs. Here, we examined how long-term adaptation to elevated temperatures influences competition among three taxa representing different phytoplank...

Jellyfish have become a crucial functional group in marine and freshwater pelagic ecosystems in recent decades. The freshwater jellyfish Craspedacusta sowerbii has also been observed more frequently globally. Mechanisms affecting its positioning in the water column, and therefore, its observation and impact on the overall pelagic community, have not systematically been studied. Factors potentially affecting the vertical moveme...

In the context of global change, marine organisms are subjected not only to gradual changes in abiotic parameters, but also to an increasing number of extreme events, such as heatwaves. However, we still know little about the influence of heatwaves on the structure of marine communities, and experimental studies are needed to test the impact of heatwaves alone and in combination with other environmental drivers. Here, we condu...

This multi‐year study highlights the ecological role of diversity and fatty acid availability in phytoplankton communities and their complex interactions with zooplankton. These findings, achieved through large‐scale mesocosm experiments, provide novel evidence of the critical role of biochemical components in shaping zooplankton community composition in natural environments, which short‐term and less complex laboratory studie...

In many ecosystems, consumers respond to warming differently than their resources, sometimes leading to temporal mismatches between seasonal maxima in consumer demand and resource availability. A potentially equally pervasive, but less acknowledged threat to the temporal coherence of consumer‐resource interactions is mismatch in food quality. Many plant and algal communities respond to warming with shifts toward more carbon‐ri...

In recent decades, the increase in terrestrial inputs to freshwater and coastal ecosystems, especially occurring at northern latitudes, has led to a process of water color darkening known as “brownification.” To assess how brownification affects plankton community composition and functioning in northern coastal areas, an in situ mesocosm experiment using a highly colored humic substance to simulate a brownification event was p...

Growing evidence suggests that global climate change promotes the dominance of mixotrophic algae especially in oligotrophic aquatic ecosystems. While theory predicts that mixotrophy increases trophic transfer efficiency in aquatic food webs, deleterious effects of some mixotrophs on consumers have also been reported. Here, using a widespread mixotrophic algal genus Dinobryon , we aimed to quantify how colonial taxa contribute...

A shift has been predicted in future nitrogen emission scenarios from nitrous oxide to higher proportions of ammonium compounds. To investigate the interaction between increasing nitrogen load and varying nitrate:ammonium ratios (NO 3 − :NH 4 + ), we performed a mesocosm experiment in an oligotrophic lake in southern Germany. We fertilized mesocosms with both roughly natural and four times the natural nitrogen wet deposition a...

Diversity–productivity relationships at the primary producer level have been extensively studied, especially for terrestrial systems. Here, we explore whether the diversity of aquatic primary producers (phytoplankton) has effects on higher trophic levels (zooplankton). We investigated the effect of phytoplankton diversity on an artificial zooplankton community in a laboratory experiment where phytoplankton biomass and elementa...

We conducted laboratory experiments with 85 assembled phytoplankton communities composed of species from four predefined functional groups (chlorophytes, diatoms, cyanobacteria, chrysophytes) to distinguish the relative importance of species diversity from functional group diversity on carbon uptake. We separated the observed diversity effects on carbon uptake into those caused by species with particularly important traits (se...

In deep temperate lakes, the beginning of the growing season is triggered by thermal stratification, which alleviates light limitation of planktonic producers in the surface layer and prevents heat loss to deeper strata. The sequence of subsequent phenological events (phytoplankton spring bloom, grazer peak, clearwater phase) results in part from coupled phytoplankton–grazer interactions. Disentangling the separate, direct eff...

In many lakes, zooplankton show a distinct diel vertical migration (DVM) behavior, especially during periods of stratification. Excretion products of these zooplankton could potentially cause an upward nutrient transport and consequent nutrient enrichment for phytoplankton in the epilimnion. We quantified the upward transport of phosphorus by the cladoceran Daphnia DVM experimentally by adding a radioactive tracer ( 33 P) to t...

Actively motile, flagellated phytoplankton taxa often exploit vertical gradients in the availability of light and nutrients. The ability to move actively usually goes along with low investment in structural carbon components and should entail costs in terms of increased energy expenditure. This should be reflected in higher metabolic rates and higher light requirements for growth and, consequently, in lower light‐dependent spe...

There is widespread concern that loss of biodiversity can influence important ecosystem services. A positive relationship between diversity and productivity has been observed in investigations of terrestrial and aquatic plant communities. However, an increase in primary production (carbon assimilation) does not necessarily result in higher nutrient uptake by primary producers. There is a loose coupling between carbon assimilat...

Phytoplankton–grazer dynamics are often characterized by long transients relative to the length of the growing season. Using a phytoplankton–grazer model parameterized for Daphnia pulex with either flexible or fixed algal carbon : nutrient stoichiometry, we explored how nutrient and light supply (the latter by varying depth of the mixed water column) affect the transient dynamics of the system starting from low densities. The...

Both low and high rates of light supply can restrict herbivore growth rates by limiting either the quantity (photosynthetically fixed carbon) or the nutritional quality (nutrient content per fixed carbon) of the herbivores– food. The “light‐nutrient hypothesis,” therefore, predicts that, if phosphorus (P) supply is sufficiently low, production of herbivorous zooplankton should be unimodally related to light intensity. We manip...