Search results for "Microcosm"

Multiple stressors in Mediterranean coastal wetland ecosystems : Influence of salinity and an insecticide on zooplankton communities under different …

2021

Temperature increase, salinity intrusion and pesticide pollution have been suggested to be among the main stressors affecting the biodiversity of coastal wetland ecosystems. Here we assessed the single and combined effects of these stressors on zooplankton communities collected from a Mediterranean coastal lagoon. An indoor microcosm experiment was designed with temperature variation (20 °C and 30 °C), salinity (no addition, 2.5 g/L NaCl) and the insecticide chlorpyrifos (no addition, 1 μg/L) as treatments. The impact of these stressors was evaluated on water quality variables and on the zooplankton comunity (structure, diversity, abundance and taxa responses) for 28 days. This study shows …

Antibiotrophy: Key Function for Antibiotic-Resistant Bacteria to Colonize Soils—Case of Sulfamethazine-Degrading Microbacterium sp. C448

2021

Chronic and repeated exposure of environmental bacterial communities to anthropogenic antibiotics have recently driven some antibiotic-resistant bacteria to acquire catabolic functions, enabling them to use antibiotics as nutritive sources (antibiotrophy). Antibiotrophy might confer a selective advantage facilitating the implantation and dispersion of antibiotrophs in contaminated environments. A microcosm experiment was conducted to test this hypothesis in an agroecosystem context. The sulfonamide-degrading and resistant bacterium Microbacterium sp. C448 was inoculated in four different soil types with and without added sulfamethazine and/or swine manure. After 1 month of incubation, Micro…

Effects of temperature and moisture fluctuations on an experimental soil microarthropod community

2001

Summary We established an experiment in microcosms with coniferous forest humus and birch leaf litter for testing the effects of constant vs. diurnally fluctuating temperature and uniform vs. varying moisture, on the population densities and species richness of Collembola and Mestostigmata. These parameters and the vertical distribution of populations were analysed by layers (top, centre, bottom) at two samplings (weeks 10 and 27). The hypotheses were that populations of at least some species benefit from fluctuating microclimate, and that varying conditions permit more species to coexist than uniform conditions. At fluctuating temperature regime, four species and total Collembola were more…

Temporal and spatial fluctuations in moisture affect humus microfungal community structure in microcosms

2000

The effects of temporal and spatial fluctuations in moisture on the microfungal community were studied in birch litter plus pine humus microcosms over 6 months. Two treatments were used: a uniform treatment in which moisture was maintained at the original moisture content throughout the profile over the course of the experiment; and a fluctuating moisture treatment in which the moisture content of the whole microcosm fluctuated weekly around the original moisture content. At 6 months, fungal species richness was higher and diversity was lower under moisture fluctuations than under uniform moisture. The number of fungal isolates and proportional diversity was significantly higher in the bott…

Decomposer communities in contaminated soil: Is altered community regulation a proper tool in ecological risk assessment of toxicants?

1997

Abstract Effects of patchy soil contamination on decomposer organisms, their community regulation and nutrient mineralization were studied in a microcosm experiment. Coniferous forest soil was patchily contaminated with three concentrations of sodiumpentachlorophenate PCP (0, 50 and 500 mg PCP kg−1 of dry soil). Abundance of microbes, enchytraeids, nematodes, small oribatids and predatory mites were reduced by the PCP. Direct toxicity of PCP and lowered microbial biomass seemed to affect animal community composition in the most contaminated patches. Some large oribatids which seemed to be tolerant to PCP increased their numbers in the most contaminated patches. Although predatory mites suff…

Soil animals and ecosystem processes: How much does nutrient cycling explain?

2008

Summary Trophic-dynamic hypotheses have been extensively tested by manipulating the presence of soil animals in experimental laboratory microcosms. Soil animals typically have pronounced effects on microbial populations, nutrient cycling and plant growth. However, because often only the total effect has been reported, the relative importance of feeding interactions versus non-trophic effects remains obscure. Using simple calculations based on mass conservation I argue that the observed faunal effect on microbes and system functioning is often larger than can be explained by trophic dynamics and nutrient cycling. Non-trophic effects may help to explain why microcosm experiments have failed t…

Abundant and diverse arsenic‐metabolizing microorganisms in peatlands treating arsenic‐contaminated mining wastewaters

2020

Mining operations produce large quantities of wastewater. At a mine site in Northern Finland, two natural peatlands are used for the treatment of mining‐influenced waters with high concentrations of sulfate and potentially toxic arsenic (As). In the present study, As removal and the involved microbial processes in those treatment peatlands (TPs) were assessed. Arsenic‐metabolizing microorganisms were abundant in peat soil from both TPs (up to 108 cells gdw‐1), with arsenate respirers being about 100 times more abundant than arsenite oxidizers. In uninhibited microcosm incubations, supplemented arsenite was oxidized under oxic conditions and supplemented arsenate was reduced under anoxic con…

Survival strategies and pathogenicity of Ralstonia solanacearum phylotype II subjected to prolonged starvation in environmental water microcosms

2008

Survival strategies exhibited over 4 years by Ralstonia solanacearum phylotype (ph) II biovar (bv) 2 in environmental water microcosms were examined. The bacterium is a devastating phytopathogen whose ph II bv 2 causes bacterial wilt in solanaceous crops and ornamental plants. Outbreaks of the disease may originate from dissemination of the pathogen in watercourses, where it has to cope with prolonged nutrient limitation. To ascertain the effect of long-term starvation on survival and pathogenicity of R. solanacearum in natural water microcosms, survival experiments were conducted. Microcosms were prepared from different sterile river water samples, inoculated separately with two European s…

Survival ofRalstonia solanacearum Biovar 2 in River Water: Influence of Water Microbiota

2008

Modelling the interactions of soil microbes and nematodes

2009

Abstract Six different soil food webs, assembled from a bacterium, a bacterial-feeding nematode, a fungus and a fungal-feeding nematode, were established in replicated laboratory microcosms. Glucose was supplied as the sole carbon source for the microbes. Biomasses of the organisms and the concentration of dissolved organic carbon (DOC) were measured ten times during 20 weeks. A discrete dynamic model based on the material flow between system components was fitted to the experimental data. Bacterial-based food chains were largely inactive in the absence of fungi, but mutual facilitation was observed in the systems with both fungus and bacterium. The population dynamics of a fungal-feeding …