Non-consumptive effects of predator presence on copepod reproduction: insights from a mesocosm experiment

Reproduction in planktonic animals depends on numerous biotic and abiotic factors. One of them is predation pressure, which can have both direct consumptive effects on population density and sex ratio, and non-consumptive effects, for example on mating and migration behaviour. In copepods, predator vulnerability depends on their sex, motility pattern and mating behaviour. Therefore, copepods can be affected at multiple stages during the mating process. We investigated the reproductive dynamics of the estuarine copepod Eurytemora affinis in the presence and absence of its predator the mysid Neomysis integer in a mesocosm experiment. We found that the proportion of ovigerous females decreased in the presence of predators. This shift was not caused by differential predation as the absolute number of females was unaffected by mysid presence. Presence of predators reduced the ratio of males to non-ovigerous females, but not by predation of males. Our combined results suggest that the shift from ovigerous to non-ovigerous females under the presence of predators was caused by either actively delayed egg production or by shedding of egg sacs. Nauplii production was initially suppressed in the predation treatment, but increased towards the end of the experiment. The proportion of fertilized females was similar in both treatments, but constantly fell behind model predictions using a random mating model. Our results highlight the importance of non-consumptive effects of predators on copepod reproduction and hence on population dynamics.     

Effects of pesticides on soil enzymes: a review

The use of pesticides in agriculture has highly increased during the last 40 years to increase crop yields. However, today most pesticides are polluting water, soil, atmosphere and food. Pesticides are also impact soil enzymes, which are essential catalysts ruling the quality of soil life. In particular, the activity of soil enzymes control nutrient cycles, and, in turn, fertilization. Here, we review the effects of pesticides on the activity of soil enzymes in terrestrial ecosystems. Enzymes include dehydrogenase, fluorescein diacetate hydrolase, acid phosphatase, alkaline phosphatase, phosphatase, β-glucosidase, cellulase, urease and aryl-sulfatase. Those enzymes are involved in the cycles of carbon, nitrogen, sulfur and phosphorus. The main points of our analysis are (1) the common inhibition of dehydrogenase in 61 % of studies, stimulation of cellulase in 56 % of studies and no response of aryl-sulfatase in 67 % of studies. (2) Fungicides have mainly negative effects on enzymatic activities. (3) Insecticides can be classified into two groups, the first group represented by endosulfan having an overall positive impact while the second group having a negative effect. (4) Herbicides can be classified into two groups, one group with few positive effect and another group with negative effect.     

Time and moisture effects on total and bioavailable copper in soil water extracts

Environmental risk assessment of heavy metals in soil frequently involves testing of freshly spiked soils kept under stable humidity conditions, but it has been questioned whether these assessments are representative of the field situation. Furthermore, the poor correspondence that is often found between total metal content and metal toxicity calls for integrated chemical and biological analysis. The aim of this work was to determine time- and moisture-dependent changes in total water-extractable Cu as well as bioavailable Cu in soil water extracts. Measurements of total water-extractable copper ([Cu]tot) were performed using furnace atomic absorption spectrometry. An in vitro assay employing a Cu-specific Pseudomonas fluorescens reporter strain was used to estimate Cu that was biologically available to the reporter strain. We refer to this copper fraction as "bioavailable," [Cu]bio. We found a time-dependent decrease in [Cu]tot and [Cu]bio during incubation for up to 220 d at field capacity. Hence the [Cu]bio was reduced to between 32 and 40% of the initial values. Furthermore, the [Cu]bio to [Cu]tot ratio correlated positively with the amount of added Cu and tended to increase with time. The moisture content of the soil was important for Cu retention. Dry soil had higher [Cu]tot concentrations than humid soil, but the [Cu]bio to [Cu]tot, ratio was lower in the dry soil. Alternating drying and wetting did not lead to a more rapid Cu retention than observed under constant humid conditions. Our observations underline the need for considering both time and moisture effects when interpreting short-term toxicity studies and when making predictions concerning possible long-term effects of Cu in the soil environment.     

A Model of Navigation-Induced Currents in Inland Waterways and Implications for Juvenile Fish Displacement

The likely extension of commercial inland navigation in the future could increase hazards directly impacting on the nurseries of freshwater fish, especially for smaller individuals with limited swimming abilities. One limitation of the evaluation of inland navigation on fish assemblages is the lack of suitable hydraulic models. This article presents a hydraulic model to assess the increase of navigation-induced physical forces due to higher vessel speed, length, and drought in a low-flowing waterway related to maximum swimming performance of fish to (1) foresee hazards of enhancement of inland navigation, (2) derive construction measures to minimize the hydraulic impact on small fish, and (3) improve fish recruitment in waterways.The derived model computed current velocities induced by passing commercial vessels in inland waterways experimentally verified and parameterized in a German lowland waterway. Results were linked with a model of maximum fish swimming performance to elucidate consequences for freshwater fish populations. The absolute magnitude of navigation-induced current limits the availability of littoral habitats for small fish. Typical navigation-induced current velocities of 0.7–1 m/s in the straight reaches of waterways will be maintained by fish longer than 42 mm only. Smaller juveniles unable to withstand those currents could become washed out, injured, or displaced. In contrast, in small local bays, the navigation-induced current declined significantly. According to our model, in a 20-m extended bay, the return current drops below 0.11 m/s, corresponding to the maximum swimming speed of a 9-mm-long fish. Thus, enhancing shoreline development by connecting oxbows, tributaries, and especially by purpose-built bays limits the impact on fish recruitment without restricting navigation resulting in more precautionary and sustainable inland navigation.     

Comparison of atrazine losses in three small headwater catchments

Understanding the processes causing herbicide transport to surface waters is crucial to determine mitigation options to reduce these losses. To this end, we investigated the atrazine (2-chloro-4-ethylamino-6-isopropylamino-1,3,5-triazine) transport in three agricultural catchments (1.1-2.1 km2) in the watershed of Lake "Greifensee" (Switzerland). In 1999, atrazine application data were recorded for all three catchments. Time proportional samples were taken at a high temporal resolution at the catchment outlets. Extremely wet conditions caused large relative losses from the catchments, ranging between 0.6 and 3.5% of the amount applied. Most of the atrazine load was due to event-driven diffuse losses from the fields. Farmyard runoff contributed less but caused the highest concentrations (up to 31 microg L(-1)) in the brooks. The maximum concentrations due to diffuse losses varied between 1.2 and 8.2 microg L(-1) among the catchments. Despite different absolute concentration levels, the concentration time-series were very similar. It seems that the travel-times within the catchments were mainly controlled by the rainfall pattern with little influence of the catchment properties. These properties, however, caused the relative losses to vary by a factor of 6 between the catchments. This variability could be partly explained by differences in the connectivity of the fields to the brooks and by their hydrological soil properties. A comparison of the losses from the three catchments with those from the entire watershed of Lake Greifensee demonstrated that they were representative for the larger area. Hence, the study results provide a good data set to evaluate distributed models predicting herbicide losses.     

Assessment of the Ecological Integrity of Traunsee (Austria) Via Analysis of Sediments and Benthic Microbial Communities

Since nearly one hundred years Traunsee experiences the import of tons of liquid and solid waste originating from salt and soda production. Today, the lake exhibits chloride concentrations of up to 170 mg L^-1 and 19% of the lake floor are directly or indirectly influenced by industrial deposits (ID). Based on the comparison of several microbial parameters in unaffected, directly affected and intermediate lake bottom sediments, the ecological integrity of the lake was evaluated. The highly alkaline ID, which were exclusively colonized by microorganisms, harbored a bacterial community reduced by a factor of 10 in abundance and biomass compared to undisturbed sediment areas within the lake. The bacterial community of ID was furthermore characterized by a reduced content of actively respiring cells (INT-formazan reduction), a lower frequency of dividing cells (FDC) and a significantly reduced cell and biomass production. A 80 to 90% reduction in carbon recycling is estimated for the area exclusively covered by ID. Protists, although occasionally absent from the industrial sediments, were in general found to be less sensitive to the contaminant stress. Differences in alkalinity and dissolved organic carbon (DOC) concentrations of sediment porewaters as well as the total organic content and C/N ratios of sediments partly explain the microbial pattern observed at the various sampling sites. Possible consequences of the continuous industrial tailings for the whole lake ecosystem and the validation of the ecological integrity are discussed.     

Economic growth,national income and the blocked choices for the environment

Summary This paper explains why the identification of the increase of national income (or GNP) with economic growth, increase in welfare and economic success is theoretically wrong. This incorrect use of terms strengthens the one-sided orientation of economic policy on the growth of production, often at the expense of the environment. Two examples are given of how this course of affairs is blocking the social choices regarding a fundamental solution of the environmental problem. An overview is given of the possibilities of correcting the Gross National Product (GNP) figures for environmental losses. None of these are perfect, since shadow prices for environmental functions directly comparable with the market prices of goods produced can be construed only in exceptional cases. The conclusion is that the only way to arrive at national income figures corrected for environmental losses is to supplement the corrections for expenditures on preventive, restoratory and compensatory measures (defensive expenditures) with the estimated expenditures on measures required to meet physical standards, based on health and a sustainable economic development.Dr Roefie Hueting is Head of the Department of Environment Statistics at the Netherlands Central Bureau of Statistics and a Visiting Fellow at the International Institute for Environment and Society (IIUG). He is a previous contributor toThe Environmentalist (1985, pp.253–262). Dr Christian Leipert is a staff member at IIUG.     

Taking Ethics into Account in Farm Animal Breeding: What can the Breeding Companies Achieve?

Animal welfare and the ethical issues it raises have been discussed intensively for a couple of decades. The emphasis has been on the direct effects of housing and husbandry, but more attention is now being given to problems originating in selective breeding. European attempts to adjust animal welfare legislation to deal with these problems have been largely unsuccessful, but the fact that selective breeding can introduce welfare problems continues to place an ethical responsibility on the animal breeding industry. Since breeding decisions are made centrally and, increasingly, internationally, strategic change is only likely to occur if it is embedded in an international agreement of some kind. The aim of this paper is to describe the key ethical issues facing animal breeding and assess the suggestion that the breeding industry itself can deal with ethical issues by means of an ethical code. Results from recent projects involving commercial breeding enterprises are presented.     

Sustainable development strategies: Tools for policy coherence

Many different approaches for national sustainable development strategies (NSDS) have been proposed since 1992, with some components common to all. A country's national strategy should be designed to help mainstream environmental concerns into policy. More broadly, it should coordinate local policy with global concerns, as well as integrate scientific knowledge into policy and development planning. The peer review mechanism for national strategies was piloted by France, and also involved representatives of countries from the North and the South as well as stakeholders. The peer review process allows countries to share their experience and information, and can assist them in identifying their own path to sustainable development. The business community can also contribute to sustainable development through provision of local and global public goods. Another input to sustainable development could come from the International Organization for Standardization (ISO) and its Guidance Standard on Social Responsibility (ISO 26000), as a coordinating mechanism between voluntary initiatives and binding obligations (such as international conventions). ISO standards and guidelines should therefore be integrated with national sustainable development strategies and local Agenda 21 frameworks.     

Soil resource supply influences faunal size–specific distributions in natural food webs

The large range of body-mass values of soil organisms provides a tool to assess the ecological organization of soil communities. The goal of this paper is to identify graphical and quantitative indicators of soil community composition and ecosystem functioning, and to illustrate their application to real soil food webs. The relationships between log-transformed mass and abundance of soil organisms in 20 Dutch meadows and heathlands were investigated. Using principles of allometry, maximal use can be made of ecological theory to build and explain food webs. The aggregate contribution of small invertebrates such as nematodes to the entire community is high under low soil phosphorus content and causes shifts in the mass–abundance relationships and in the trophic structures. We show for the first time that the average of the trophic link lengths is a reliable predictor for assessing soil fertility responses. Ordered trophic link pairs suggest a self-organizing structure of food webs according to resource availability and can predict environmental shifts in ecologically meaningful ways. Electronic supplementary material  The online version of this article (doi:) contains supplementary material, which is available to all users.