Impact of peri-urban landscape on the organic and mineral contamination of pond waters and related risk assessment.

Ponds are important for their ecological value and for the ecosystem services they provide to human societies, but they are strongly affected by human activities. Peri-urban development, currently one of the most pervasive processes of land use change in Europe, exposes ponds to both urban and agricultural contaminants, causing a potential combination of adverse effects. This study, focused on 12 ponds located in a peri-urban area, has two main objectives: (1) to link the physico-chemical characteristics of the waters and the nature of their contaminants, either organic or mineral, with the human activities around ponds, and (2) to estimate the environmental risk caused by these contaminants.

Manipulating the strength of organism-environment feedback increases nonlinearity and apparent hysteresis of ecosystem response to environmental change.

Theory predicts that organism-environment feedbacks play a central role in how ecological communities respond to environmental change. Strong feedback causes greater nonlinearity between environmental change and ecosystem state, increases the likelihood of hysteresis in response to environmental change, and augments the possibility of alternative stable regimes. To illustrate these predictions and their dependence on a temporal scale, we simulated a minimal ecosystem model.

[Biotin analytical interference on Siemens immunoanalysis on Dimension EXL®: impact on cardiac troponin I and total vitamin D (D+D) assays].

Several hyperthyroidism misdiagnoses cases have been recently described due to biotin intake. Biotin used in immuno-analysis assays which rely on biotin/streptavidin binding properties. In these assays, high plasmatic biotin levels can lead to major analytical interferences resulting in falsely higher (competition tests) or falsely reduced determinations (for sandwiches assays).

Linking phytoplankton pigment composition and optical properties: A framework for developing remote-sensing metrics for monitoring cyanobacteria.

This study has been performed in the framework of a research program aiming to develop a low-cost aerial sensor for the monitoring of cyanobacteria in freshwater ecosystems that could be used for early detection. Several empirical and mechanistic remote-sensing tools have been already developed and tested at large scales and have proven useful in monitoring cyanobacterial blooms. However, the effectiveness of these tools for early detection is hard to assess because such work requires the detection of low concentrations of characteristic pigments amid complex ecosystems exhibiting several confounding factors (turbidity, blooms of other species, etc.

Modeling the direct and indirect effects of copper on phytoplankton-zooplankton interactions.

Predicting the effects of pollution at the community level is difficult because of the complex impacts of ecosystem dynamics and properties. To predict the effects of copper on a plant-herbivore interaction in a freshwater ecosystem, we built a model that focuses on the interaction between an alga, Scenedesmus sp., and a herbivore, Daphnia sp.

Ingredients for protist coexistence: competition, endosymbiosis and a pinch of biochemical interactions.

1. The interaction between mutualism, facilitation or interference and exploitation competition is of major interest as it may govern species coexistence. However, the interplay of these mechanisms has received little attention.

Density-dependent dispersal and relative dispersal affect the stability of predator-prey metacommunities.

Although density-dependent dispersal and relative dispersal (the difference in dispersal rates between species) have been documented in natural systems, their effects on the stability of metacommunities are poorly understood. Here we investigate the effects of intra- and interspecific density-dependent dispersal on the regional stability in a predator-prey metacommunity model. We show that, when the dynamics of the populations reach equilibrium, the stability of the metacommunity is not affected by density-dependent dispersal.

Intra- and interspecific density-dependent dispersal in an aquatic prey-predator system.

1. Dispersal intensity is a key process for the persistence of prey-predator metacommunities. Consequently, knowledge of the ecological mechanisms of dispersal is fundamental to understanding the dynamics of these communities.

Nutrient-limited food webs with up to three trophic levels: feasibility, stability, assembly rules, and effects of nutrient enrichment.

Community structure is controlled, among multiple factors, by competition and predation. Using the R* rule and graphical analysis, we analyse here the feasibility, stability and assembly rules of resource-based food webs with up to three trophic levels. In particular, we show that (1) the stability of a food web with two plants and two generalist herbivores does not require that plants' resource exploitation abilities trade-off with resistance to the two herbivores, and (2) food webs with two plants and either one generalist herbivore and a carnivore or two generalist herbivores and two generalist carnivores are not feasible because of cascade competition between top consumers.