Search results for " Ecosystem"
showing 10 items of 633 documents
Combined effects of heatwaves and micropollutants on freshwater ecosystems: Towards an integrated assessment of extreme events in multiple stressors …
2022
Freshwater ecosystems are strongly influenced by weather extremes such as heatwaves, which are predicted to increase in frequency and magnitude in the future. In addition to these climate extremes, the freshwater realm is impacted by the exposure to various classes of chemicals emitted by anthropogenic activities. Currently, there is limited knowledge on how the combined exposure to heatwaves and chemicals affects the structure and functioning of freshwater ecosystems. Here, we review the available literature describing the single and combined effects of heatwaves and chemicals on different levels of biological organization, to obtain a holistic view of their potential interactive effects. …
Science Advances
2019
River ecosystems receive and process vast quantities of terrestrial organic carbon, the fate of which depends strongly on microbial activity. Variation in and controls of processing rates, however, are poorly characterized at the global scale. In response, we used a peer-sourced research network and a highly standardized carbon processing assay to conduct a global-scale field experiment in greater than 1000 river and riparian sites. We found that Earth’s biomes have distinct carbon processing signatures. Slow processing is evident across latitudes, whereas rapid rates are restricted to lower latitudes. Both the mean rate and variability decline with latitude, suggesting temperature constrai…
Assessing the influence of confounding biological factors when estimating bioaccumulation of PCBs with passive samplers in aquatic ecosystems
2017
Passive samplers are promising surrogates for organisms, mimicking bioaccumulation. However, several biological characteristics disturb the passive partitioning process in organisms by accelerating or restraining bioaccumulation, resulting in species-specific body residues of hydrophobic organic contaminants (HOCs). In addition to site-specific characteristics and HOC concentrations, age, sex, diet, biotransformation capability and habitat-specific characteristics may affect body residues. Two passive sampler types, polyethylene (PE) and polydimethylsiloxane (PDMS) were deployed in a PCB-contaminated freshwater lake water and sediment, respectively, to assess their bioaccumulation predictio…
Critical review: Grand challenges in assessing the adverse effects of contaminants of emerging concern on aquatic food webs
2019
Much progress has been made in the past few decades in understanding the sources, transport, fate, and biological effects of contaminants of emerging concern (CECs) in aquatic ecosystems. Despite these advancements, significant obstacles still prevent comprehensive assessments of the environmental risks associated with the presence of CECs. Many of these obstacles center around the extrapolation of effects of single chemicals observed in the laboratory or effects found in individual organisms or species in the field to impacts of multiple stressors on aquatic food webs. In the present review, we identify 5 challenges that must be addressed to promote studies of CECs from singular exposure e…
Simplification, not “tropicalization”, of temperate marine ecosystems under ocean warming and acidification
2021
Ocean warming is altering the biogeographical distribution of marine organisms. In the tropics, rising sea surface temperatures are restructuring coral reef communities with sensitive species being lost. At the biogeographical divide between temperate and tropical communities, warming is causing macroalgal forest loss and the spread of tropical corals, fishes and other species, termed “tropicalization”. A lack of field research into the combined effects of warming and ocean acidification means there is a gap in our ability to understand and plan for changes in coastal ecosystems. Here, we focus on the tropicalization trajectory of temperate marine ecosystems becoming coral-dominated systems…
Analysis of the vertical distribution in a model of phytoplankton dynamics
2010
Phytoplankton often faces the dilemma of living in contrasting gradients of two essential resources: the light that comes from above and nutrients that are often supplied from below. In poorly mixed water columns, algae can be heterogeneously distributed, with thin layers of biomass found on the surface, in depth, or on the sediment surface. Here, we show that these patterns can result from intraspecific competition between light and nutrients. First, we present numerical solutions of a reaction-diffusion-taxis model for phytoplankton, nutrients and light. We argue that motile phytoplankton can form a thin layer under poorly mixed conditions. The numerical solution of this model indicates t…
Tree-ring indicators of German summer drought over the last millennium
2010
Past natural and future anthropogenic drought variability has and will impact terrestrial ecosystems, agricultural productivity, socio-economic conditions, and public health on various time-scales. In comparison to reconstructed and projected temperature change, much less is known about variations in the hydrological cycle. Here we present 953 living and historical oak (Quercus sp) ring width samples from Central Germany (51–52
Climate controls on the Holocene development of a subarctic lake in northern Fennoscandia
2015
International audience; Climate exerts strong control over the functioning of northern freshwater ecosystems, yet their resilience and responses to climate forcing may vary. We examined postglacial development patterns in subarctic Lake Varddoaijavri to discern the impact of direct climate controls, catchment influence, and ontogenic processes on the ecological functioning of the lake over the Holocene. Subfossil diatom assemblages together with the elemental and stable isotopic (delta C-13, delta N-15) composition of sediment organic matter were used to examine climate-induced changes in the structure of the phototrophic community and transport of terrestrial organic matter from the catchm…
The lacustrine sediment record of Oberwinkler Maar (Eifel, Germany): Chironomid and macro-remain-based inferences of environmental changes during Oxy…
2008
The lacustrine record of Oberwinkler Maar (Eifel, Germany) is the northernmost continuous record documenting the Weichselian Pleniglacial in central Europe - a period characterized by multiple abrupt climate oscillations known as the Dansgaard/Oeschger cycles. Here, the results of a high-resolution study of chironomid remains are presented, with a focus on the earlier part of Oxygen Isotope Stage (OIS) 3 (60-50 kyr BP) covering four stadial/interstadial cycles. During the stadials, the chironomid fauna of the former lake was dominated by many coldstenothermic chironomid taxa, indicating a cold, oligotrophic lake. The concentrations of chironomid remains were lower during the interstadials, …
Stepping on invisible land: on the importance of communicating the value of soils.
2022
Soils play fundamental roles in the functioning of the Earth's ecosystems. Despite numerous initiatives to protect soils, it continues to be generally perceived as dirt or, at best, the surface we walk on. To better understand soil perception by the public, we conducted a survey with 99 participants from Poland and Brazil. We applied opportunity sampling and conducted semi-structured interviews with 40 respondents from Poland and 30 from Brazil, and 29 unstructured interviews in Brazil. Most of the respondents (53%) of the semi-structured interviews associated soil with the surface where plants grow, while 27% said that it is the ground we step on. When asked about pro-environmental campaig…