Long-term response of the nematode community to elevated atmospheric CO2 in a temperate dry grassland soil

Long-term effects of the elevated atmospheric CO2 on biosphere have been in focus of research since the last few decades. In this experiment undisturbed soil monoliths of loess grassland were exposed to an elevated CO2 environment (two-times the ambient CO2 level) for a period of six years with the aid of the open top chamber method. Control without a chamber and CO2 elevation was applied as well. Elevated CO2 level had very little impact oil soil food web. It did not influence either root and microbial biomass or microbial and nematode community structure. The only significant response was that density of the bacterial feeder genus Heterocephalobus increased in the chamber with elevated CO2 concentration. Application of the open top chambers initiated more changes on nematodes than the elevated CO2 level. Open top chamber (OTC) method decreased nematode density (total and plant feeder as well) to less than half of the original level. Negative effect was found on the genus level in the case of fungal feeder Aphelenchoides, plant feeder Helicotylenchus and Paratylenchus. It is very likely that the significantly lower belowground root biomass and partly its decreased quality reflected by the increased C/N ratio are the main responsible factors for the lower density of the plant feeder nematodes in the plots of chambers. According to diversity profiles, MI and MI(2-15) parameters, nematode communities in the open top chambers (both on ambient and elevated CO2 level) seem to be more structured than those under normal circumstances six years after start of the experiment.

Potential impacts of climate change on water quality and ecology in six UK rivers

A modelling study has been undertaken to assess the likely impacts of climate change on water quality across the UK. A range of climate change scenarios have been used to generate future precipitation, evaporation and temperature time series at a range of catchments across the UK. These time series have then been used to drive the Integrated Catchment (INCA) suite of flow, water quality and ecological models to simulate flow, nitrate, ammonia, total and soluble reactive phosphorus, sediments, macrophytes and epiphytes in the Rivers Tamar, Lugg, Tame, Kennet, Tweed and Lambourn. A wide range of responses have been obtained with impacts varying depending on river character, catchment location, flow regime, type of scenario and the time into the future. Essentially upland reaches of river will respond differently to lowland reaches of river, and the responses will vary depending on the water quality parameter of interest.

MEASUREMENT AND MODELING OF THE TOXICITY OF BINARY MIXTURES IN THE NEMATODE CAENORHABDITIS ELEGANS-A TEST OF INDEPENDENT ACTION

Ecological risk assessments must increasingly consider the effects of chemical mixtures on the environment as anthropogenic pollution continues to grow in complexity. Yet testing every possible mixture combination is impractical and unfeasible; thus, there is an urgent need for models that can accurately predict mixture toxicity from single-compound data. Currently, two models are frequently used to predict mixture toxicity from single-compound data: Concentration addition and independent action (IA). The accuracy of the predictions generated by these models is currently debated and needs to be resolved before their use in risk assessments can be fully justified. The present study addresses this issue by determining whether the IA model adequately described the toxicity of binary mixtures of five pesticides and other environmental contaminants (cadmium, chlorpyrifos, diuron, nickel, and prochloraz) each with dissimilar modes of action on the reproduction of the nematode Caenorhabditis elegans. In three out of 10 cases, the IA model failed to describe mixture toxicity adequately with significant or antagonism being observed. In a further three cases, there was an indication of synergy, antagonism, and effect-level-dependent deviations, respectively, but these were not statistically significant. The extent of the significant deviations that were found varied, but all were such that the predicted percentage effect seen on reproductive output would have been wrong by 18 to 35% (i.e., the effect concentration expected to cause a 50% effect led to an 85% effect). The presence of such a high number and variety of deviations has important implications for the use of existing mixture toxicity models for risk assessments, especially where all or part of the deviation is synergistic.

Water quality and ecology of the River Lee: mass balance and a review of temporal and spatial data

A regional overview of the water quality and ecology of the River Lee catchment is presented. Specifically, data describing the chemical, microbiological and macrobiological water quality and fisheries communities have been analysed, based on a division into river, sewage treatment works, fish-farm, lake and industrial samples. Nutrient enrichment and the highest concentrations of metals and micro-organics were found in the urbanised, lower reaches of the Lee and in the Lee Navigation. Average annual concentrations of metals were generally within environmental quality standards although, oil many occasions, concentrations of cadmium, copper, lead, mercury and zinc were in excess of the standards. Various organic substances (used as herbicides, fungicides, insecticides, chlorination by-products and industrial solvents) were widely detected in the Lee system. Concentrations of ten micro-organic substances were observed in excess of their environmental quality standards, though not in terms of annual averages. Sewage treatment works were the principal point source input of nutrients. metals and micro-organic determinands to the catchment. Diffuse nitrogen sources contributed approximately 60% and 27% of the in-stream load in the upper and lower Lee respectively, whereas approximately 60% and 20% of the in-stream phosphorus load was derived from diffuse sources in the upper and lower Lee. For metals, the most significant source was the urban runoff from North London. In reaches less affected by effluent discharges, diffuse runoff from urban and agricultural areas dominated trends. Flig-h microbiological content, observed in the River Lee particularly in urbanised reaches, was far in excess of the EC Bathing Water Directive standards. Water quality issues and degraded habitat in the lower reaches of the Lee have led to impoverished aquatic fauna but, within the mid-catchment reaches and upper agricultural tributaries, less nutrient enrichment and channel alteration has permitted more diverse aquatic fauna.

Integrating socio-economics and ecology: a taxonomy of quantitative methods and a review of their use in agro-ecology

Answering many of the critical questions in conservation, development and environmental management requires integrating the social and natural sciences. However, understanding the array of available quantitative methods and their associated terminology presents a major barrier to successful collaboration. We provide an overview of quantitative socio-economic methods that distils their complexity into a simple taxonomy. We outline how each has been used in conjunction with ecological models to address questions relating to the management of socio-ecological systems. We review the application of social and ecological quantitative concepts to agro-ecology and classify the approaches used to integrate the two disciplines. Our review included all published integrated models from 2003 to 2008 in 27 journals that publish agricultural modelling research. Although our focus is on agro-ecology, many of the results are broadly applicable to other fields involving an interaction between human activities and ecology. We found 36 papers that integrated social and ecological concepts in a quantitative model. Four different approaches to integration were used, depending on the scale at which human welfare was quantified. Most models viewed humans as pure profit maximizers, both when calculating welfare and predicting behaviour. Synthesis and applications. We reached two main conclusions based on our taxonomy and review. The first is that quantitative methods that extend predictions of behaviour and measurements of welfare beyond a simple market value basis are underutilized by integrated models. The second is that the accuracy of prediction for integrated models remains largely unquantified. Addressing both problems requires researchers to reach a common understanding of modelling goals and data requirements during the early stages of a project.

Factors affecting biological control effectiveness of Pasteuria penetrans in Meloidogyne javanica and the bacterial development in the nematode body

The invasion and infectivity of Meloidogyne javanica juveniles (J2) encumbered with spore of Pasteuria Penetrans were influenced by the temperature and the time J2 were in the soil before exposure to roots. The percentage of infected females decreased as the time juveniles spent in soil increased. When spore encumbered J2 were maintained at 30 degrees C the decrease in infection was greater than that at 18 degrees C. The thermal time requirements and the base temperature for P. penetrans development were estimated. The rate of development followed an exponential curve between 21 and 36 degrees C and the base temperature for development was estimated by extrapolation to be 18.5 degrees C. The effect of integrating a nematode resistant tomato cultivar with the biocontrol agent P. penetrans also was investigated. The ability of the biocontrol agent to reduce numbers of root-knot nematodes was dependent on the densities of the nematode and P. penetrans spores in the soil.

Susceptibility of different insect pupae to the bacterial symbiont, Xenorhabdus nematophila, isolated from the entomopathogenic nematode Steinernema carpocapsae

Cells of the bacterial symbiont Xenorhabdus nematophila from the entomopathogenic nematode, Steinernema carpocapsae entered the pupae of Plutella xylostella after 15 minutes treatment with suspensions containing the bacterial cells. Secretions of Xenorhabdus nematophila, in either broth or water, were found lethal to the pupae of P. xylostella when applied in moist sand. The bacterial symbiont Xenorhabdus nematophila was found lethal to the pupae of greater wax moth (Galleria mellonella), beet armyworm (Spodoptera exigua), diamondback moth (Plutella xylostella) and black vine weevil (Otiorhynchus sulcatus) in the absence of the nematode vector and the cells of X. nematophila entered the haemocoele of the pupae.

Protective and curative effect of neem (Azadirachta indica) formulations on the development of root-knot nematode Meloidogyne javanica in roots of tomato plants

Two types of neem formulations, crude and refined, were tested. The crude form was neem leaves and neem cakes (a by-product left after the extraction of oil from neem seed) and one of the neem-refined products was "aza". The protective and curative soil application of these formulations significantly reduced the number of egg masses and eggs per egg mass on tomato roots. Protective application of neem crude formulations (leaves and cake) did not reduce the invasion of juveniles whereas aza at 0.1% w/w did. Curative application of neem formulations significantly reduced the number of egg masses and eggs per egg mass as compared with the control. (c) 2006 Elsevier Ltd. All rights reserved.

Response of free eggs on infective juvenile root-knot nematode Meloidogyne javanica through neem (Azadirachta indica A. Juss) amended soil

Air-dried and 3 mm pore size sieved soil was amended with neem crude formulations (leaves and cake) @ 3% w/w and a refined product, aza @ 0.05 and 0.1 w/w. Three days after treatment, 500 eggs of M. javanica held in 2 ml water were added in each dish. In another experiment, soil was amended with neem crude formulations @ 10. 5, 2.5 and 1% w/w and refined formulation aza @ 0.025, 0.05, 0.1 and 0.5% w/w. Three days after amendment 1000 plus minus 21 freshly hatched J2 held in 3 ml water were added to the amended soil. Untreated soil was kept as control. Comparison of treatments means showed that all the neem formulations caused significant reduction of hatching. Neem crude formulations were more effective in reducing hatching as compared to commercial product aza. Among the crude formulations, neem leaves were most effective in reducing hatching. In other experiment all the doses of neem crude and refined formulations differed significantly with control in reducing the mobility of juveniles. It was observed that by increasing the dose of the formulations the mobility was reduced accordingly.

Comparative effect of root-knot nematode on severity of Verticillium and Fusarium wilt in cotton

The effect of root-knot nematode (RKN) (Meloidogyne incognita) on Verticillium dahliae and Fusarium oxysporum f.sp. vasinfectum in cotton (Gossypium hirsutum) was investigated. Two different inoculation methods were used, one in which inoculum was added to the soil, so that nematode and fungal inoculum were in close proximity; the other, inoculation into the stem, whereby the two inocula were spatially separated. Invasion of the roots by RKN enhanced disease severity, as measured by the height of vascular browning in the stem, following inoculation with either wilt pathogen. The effect of RKN on Fusarium wilt was more pronounced than that on Verticillium wilt. Nematode-enhanced infection by F. oxysporum is a well known effect but there are few reports of enhanced infection by Verticillium due to RKN. Relative resistance of a number of cotton cultivars to both wilt diseases, as measured by height of vascular browning, was similar to the known field performance of the cultivars. The use of vascular browning as an estimate of disease severity was therefore validated.

Enhancement of germination of spores of Verticillium dahliae and Fusarium oxysporum esp vasinfectum in vascular fluid from cotton plants infected with the root-knot nematode

Root-knot nematode [RKN] (Meloidogyne incognita) can increase the severity of Verticillium (V dahliae) and Fusarium (F oxysporum f.sp. vasinfectum) wilt diseases in cotton (Gossypium hirsutum). This study was conducted to determine some of the physiological responses caused by nematode invasion that might decrease resistance to vascular wilt diseases. The effect of RKN was investigated on spore germination and protein, carbohydrate and peroxidase content in the xylem fluids extracted from nematode-infected plants. Two cotton cultivars were used with different levels of resistance to both of the wilt pathogens. Spore germination was greater in the xylem fluids from nematode-infected plants than from nematode-free plants. The effect on spore germination was greater in the Fusarium-resistant cultivar (51%). Analysis of these fluids showed a decrease in total protein and carbohydrate levels for both wilt-resistant cultivars, and an increase in peroxidase concentration. Fluids from nematode-free plants of the Verticillium-resistant cultivar contained 46% more peroxidase than the Fusarium-resistant cultivar. The results provide further evidence that the effect of RKN on vascular wilt resistance is systemic and not only local. Changes in metabolites in the xylem pass from the root to the stem, accelerating disease development.