Leaf litter breakdown in streams receiving treated and untreated metal mine drainage

Rates of alder leaf decomposition were used as an ecosystem-level measure of effects of untreated and treated acid mine drainage on two Colorado mountain streams. Untreated mine effluents had low pH and high concentrations of metals, particularly iron. Deposition of ferric hydroxide on leaf surfaces inhibited colonization by decomposers, such as fungi and aquatic insects, and thus little leaf breakdown occurred. Treated effluents had improved water quality (basic pH, low metal concentrations), but suspended flocs released by the treatment process buried leaves and reduced consumer activity. The rate of leaf breakdown was not significantly different from the rate with untreated effluents; thus improvement in water quality alone was insufficient to restore this important pathway of energy flow in headwater streams.     

The behavioral component in the meaning of places

How do people think about the physical setting in the world around them? Part of the answer to this question may be in terms of the behaviors that occur there. To explore people's knowledge of behavior—place associations, twenty places (shown via color photographs) were assessed in five ways: (a) ratings of the place's suitability for each of eleven behaviors, (b) ratings of the expected frequency of occurrence of the eleven behaviors, (c) free listings of reasons for going to each place, (d) free listings of activities-while-there and (e) free listings of activities associated with the place. Results showed that people can distinguish places on the basis of behaviors, that the behavioral component of place meaning is composed of distinct aspects, and that knowledge of behavior is related to a global, overall representation of a place.     

Water Appropriation Systems for Adapting to Water Shortages in Iraq

Climate variability and population growth have intensified the search internationally for measures to adapt to fluctuations in water supplies. An example can be found in the lower part of the transboundary Tigris‐Euphrates Basin where water shortages in 2008‐2009 resulted in high economic costs to irrigation farmers. Losses to irrigators in the lower basin have made a compelling case to identify flexible methods to adapt to water shortage. Few published studies have systematically examined ways to enhance the flexibility of water appropriation systems to adapt to water shortage. This article addresses an ongoing challenge in water governance by examining how profitability at both the farm and basin levels is affected by various water appropriation systems. Four water appropriation systems are compared for impacts on farm income under each of three water supply scenarios. Results show that a (1) proportional sharing of water shortages among provinces and (2) unrestricted water trading rank as the top two appropriation systems. The shadow price of water for irrigation rises from zero at a full water supply level to US$93/1,000 m³ when supply falls to 20% of full levels. Similar methods could be used to analyze challenges facing the design or implementation of water appropriation systems in the world's irrigated regions.     

A simulation model of rhizome networks for Fallopia japonica (Japanese knotweed) in the United Kingdom

Fallopia japonica (Japanese knotweed) is an aggressively invasive herbaceous perennial that causes substantial economic and environmental damage in the United Kingdom (UK). As such, it is of considerable concern to councils, environmental groups, private landowners and property developers. We construct a 3D correlated random walk model of the development of the subterranean rhizome network for a single stand of F. japonica. The formulation of this model uses detailed knowledge of the morphology and physiology of the plant, both of which differ in the UK to that of its native habitat due to factors including a lack of predation and competition, longer growth seasons and favourable environmental conditions in the UK. Field data obtained as a part of this study are discussed and used in the model for parameterisation and validation. The simulation captures the field data well and predicts, for example, quadratic growth in time for the stand area. Furthermore, the role of a selection of parameters on long-term stand development are discussed, highlighting some key factors affecting vegetative spread rates.     

Studies on the sublittoral free-living nematodes of Liverpool Bay. I. The structure and distribution of the nematode populations

Data collected from a survey of the benthic fauna of Liverpool Bay (UK) have been used to study the distribution and structure, in terms of percent age dominance and percent age frequency, of the nematode populations. Cluster analysis of the faunistic data from individual stations has shown that the populations are not sharply delimited. The relative proportions of their characteristic genera are extremely variable, and apparently influenced by small differences in sediment composition. It is, thus, considered more logical to think in terms of a number of different habitats, each with certain characteristic genera, rather than in terms of a series of discrete associations. Six types of habitat are distinguished on the basis of sediment granulometry: (1) mud and sandy mud; (2) very muddy sand; (3) muddy sand; (4) muddy sand-gravel mixtures; (5) clean sand-gravel mixtures; (6) clean sand. Habitats 1, 2 and 3 were dominated by Sabatieria spp., the degree of dominance apparently being related to the percentage of silt-clay. Habitat 4 was dominated by Neochromadora sp. and Sabatieria spp. and Habitats 5 and 6 by Desmodora sp. Both generic and dominance diversity were very much lower for Habitats 1 and 2 than elsewhere.     

<Emphasis Type="Italic">Oithona similis</Emphasis> in a high latitude ecosystem: abundance,distribution and temperature limitation of fecundity rates in a sac spawning copepod

In this study we report the abundance, fecundity and an index of the relative survival of Oithona similis (nauplii to copepodites) across a large latitudinal and temperature range within the Southern Ocean. The abundance of O. similis was strongly related to temperature and to depth-integrated (0–100 m) chlorophyll a, abundance increasing with increasing temperature (and therefore decreasing latitude) and Chl a. In situ egg production rates and fecundity per female were also significantly and positively related to temperature and Chl a. Egg hatch times rapidly lengthen as temperature decreases and in sac spawning species the next batch of eggs cannot be produced until the previous clutch hatch. Consequently, we predict that in O. similis, fecundity must decline rapidly at low temperatures, especially below 5°C. A model comparing maximum rates of fecundity with in situ data suggested production rates were strongly food limited across our study region. However, the relationship of in situ and maximum rates to temperature were similar, confirming the importance of temperature. Further, as time taken to develop from egg to adult also rapidly extends with declining temperature, it is increasingly unlikely that O. similis will be able to maintain its population against mortality. Our findings have broad implications for the cold temperature (and hence geographic) limits of O. similis, but also for the distribution of other sac spawning copepods and planktonic species generally.     

Development and Evaluation of a Multiplexed Real-Time TaqMan RT-PCR Assay with a Sample Process Control for Detection of F-specific RNA Coliphage Genogroups I and IV

There are increasing concerns of zoonotic transmission of some animal enteric viruses, such as calicivirus, hepatitis E virus, and rotavirus, which are closely related to human pathogenic strains. Most enteric viruses are detected by molecular techniques because they cannot be cultured. Surrogates such as F-RNA coliphages are cultivable but few molecular methods exist. Individual real-time TaqMan RT-PCR assays for the replicase gene of F-RNA coliphage genogroups I and IV were developed and multiplexed with a real-time TaqMan RT-PCR assay for feline calicivirus as a sample process control for the simultaneous detection and enumeration of genogroup I and IV F-RNA coliphages. Genogroup IV were successfully detected with the multiplexed assay in 80% of fecal samples that contained F-RNA coliphage levels ≥3.2 log plaque forming units (pfu). F-RNA coliphage were at or below the limit of detection in most fecal samples when levels were ≤4 log pfu/g.