Water management and aquatic ecosystem services of a tropical reservoir (Itaparica,São Francisco,Brazil)

Reservoirs have a wide variety of uses that have led to frequent conflicts over ecological conservation and contamination, especially as land management has intensified. Oligotrophication must be implemented in numerous tropical reservoirs that experience advanced eutrophication to maintain aquatic ecosystem functions. To quantify impacts on ecosystem functions and to develop an adaptive management policy, multiple studies have been conducted on the Itaparica Reservoir, São Francisco River, in the semi-arid north-eastern region of Brazil. Here, we add to that existing body of knowledge through investigating how nutrient accumulation is affected by water exchange between the main river flow and Icó-Mandantes Bay. Operational water-level fluctuations in the reservoir create large desiccated littoral areas that release high amounts of nutrients when they are rewetted. In particular, water-level variation promotes proliferation of Egeria densa, a noxious weed, thus elevating trophic levels of the Itaparica Reservoir and Icó-Mandantes Bay. Analysis with a P efficiency model determined 25 μg P L^?1 to be the critical concentration and further indicated that the critical load in both bodies of water have been exceeded. Moreover, intensive fish aquaculture using net cages has led to further overtaxing of the reservoir. We conclude that an effective ecological reservoir management policy must involve oligotrophication, harvesting of noxious water weeds for use as soil amendment in agriculture or biogas production, “blue” aquaculture, and limiting hydroelectric power production based on current water availability.     

Beyond depletion: Daily self-control motivation as an explanation of self-control failure at work

The organizational self-control literature usually applies resource perspectives that explain self-control failure at work by depletion of self-control resources. However, these perspectives neglect the role of self-control motivation. On a daily level, we examine several self-control aspects (resources, motivation, demands, and effort) as predictors of a manifestation of self-control failure at work, namely, daily counterproductive work behavior toward the organization (CWB-O). Additionally, we investigate self-control effort as a mechanism predicting the depletion of self-control resources throughout the day. We analyzed data from 155 employees in a 2-week diary study with 2 daily measurement points. Multilevel path modeling showed that self-control motivation and self-control demands, but not self-control resource depletion, predicted self-control effort. There was an indirect effect from self-control motivation on CWB-O via self-control effort but no indirect effect from self-control demands on self-control resource depletion throughout the day via self-control effort. Findings suggest that self-control motivation is a crucial factor explaining self-control failure at work and cast further doubt on the idea that exerted self-control effort is the only mechanism leading to self-control resource depletion.     

Contrasting stories on overcoming governance challenges: the implementation of the EU Water Framework Directive in the Netherlands

The European Union Water Framework Directive (WFD) has provided the European Member States with a range of interacting governance challenges. This article studies three of these (the need for new administrative arrangements, public participation, and the enforced strict time frame). It questions how these interacting governance challenges were addressed in implementing the WFD in the Netherlands – a particularly interesting country since the European Commission assesses its implementation process in relatively positive terms, while an in-depth study reported on in this article tells a contrasting story. Based on this study, the article concludes that especially the interaction effects between the governance challenges may help us to better understand the outcome of the WFD-implementation process, and to provide more suitable advice as to how to improve the implementation process in future rounds.     

Monitoring pollution in River Mureş, Romania, part II: metal accumulation and histopathology in fish

As a part of an exposure and effect monitoring conducted along the river Mureş, Western Romania in 2004, the health status of two indigenous fish species, sneep (Chondrostoma nasus) and European chub (Leuciscus cephalus) was investigated upstream and downstream the city of Arad. In fish, histopathology was assessed in liver and gills, and heavy metals (cadmium, copper, lead and zinc) were analyzed in liver samples. In both fish species, histopathological reactions in the gills (epithelial lifting, focal proliferation of epithelial cells of primary and secondary lamellae and resulting fusion of secondary lamellae, hyperplasia and hypertrophy of mucous cells, focal inflammation and necrosis of epithelial cells) were most severe at the two sampling sites upstream Arad city, which were shown to be polluted by copper, cadmium, faecal coliforms and streptococci in a parallel study. At these two sites, also histopathology in the liver of L. cephalus was more prominent than at the two downstream sites. In C. nasus, symptoms in the liver (focal inflammation with lymphocytic infiltrations, macrophage aggregates and single cell necrosis) were also highly pronounced at the sampling site located directly downstream the municipal sewage treatment plant of Arad. With the exception of copper accumulation in L. cephalus caught at the most upstream sampling site, in both fish species cadmium and copper accumulation were exceptionally high and did not differ significantly between the four sampling sites.     

Greenhouse gas emissions from a semi-arid tropical reservoir in northeastern Brazil

We estimated carbon dioxide (CO₂) and methane (CH₄) emissions by diffusion, ebullition, and degassing in turbines from a semi-arid hydropower reservoir in northeastern Brazil. Sampling sites were allocated within the littoral and deeper waters of one embayment, the main-stream, and at turbines. Annual carbon emissions were estimated at 2.3?×?10⁵?±?7.45?×?10⁴ t C year^?1, or in CO₂-equivalents (CO₂-eq) at 1.33?×?10⁶?±?4.5?×?10⁵ t CO₂-eq year^?1. Diffusion across the water surface was the main pathway accounting for 96% of total carbon emissions. Ebullition was limited to littoral areas. A slight accumulation of CO₂, but not of CH₄, in bottom waters close to the turbines inlet led to degassing emissions about 8?×?10³ t C year^?1. Emissions in littoral areas were higher than in main-stream and contribute to 40% of the total carbon. Carbon (C) emissions per electricity generated, at 60% of installed capacity, is 0.05 t C-CO₂-eq MWh^?1. The ratio increases to 0.09 t C-CO₂ MWh^?1, equating 80% of the emissions from natural gas and 40% of diesel or coal power plants. Retention time and benthic metabolism were identified as main drivers for carbon emissions in littoral areas, while water column mixing and rapid water flow are important factors preventing CH₄ accumulation and loss by degassing. Our results indicate that Itaparica Reservoir, located in the semi-arid region of Northeastern Brazil, acts as a source of GHGs. Management measurements are needed to prevent emissions to raise in the future.     

Evidence for ecological matching of whole AM fungal communities to the local plant-soil environment

The range of ecological roles exhibited by arbuscular mycorrhizal (AM) fungi depends on functional differences among naturally occurring local assemblages of AM species. While functional differences have been demonstrated among AM fungal species and among geographic isolates of the same species, almost nothing is known about functional differences among whole communities of naturally occurring AM fungi. In the greenhouse, we reciprocally transplanted whole AM fungal communities between plant-soil systems representing a serpentine grassland and a tallgrass prairie, using as hosts two grasses common to both systems. For Sorghastrum nutans, native fungi consistently enhanced plant growth more than fungi switched from the alternate system. For Schizachyrium scoparium, foreign and native fungi promoted plant growth similarly in both the serpentine and prairie systems. Thus, the use of foreign inoculum in restoration could change the relative performance, and potentially the competitive abilities, of co-occurring plant species. Moving AM fungal inocula into foreign environments also caused changes in the taxonomic composition of the resultant spore communities, demonstrating their response to environmental influences. These results provide strong evidence for functional differences among naturally occurring AM communities and suggest that a particular AM fungal community may be better matched ecologically to its local habitat than communities taken from other locations.     

Vulnerability of the northern Mongolian steppe to climate change: insights from flower production and phenology

The semiarid, northern Mongolian steppe, which still supports pastoral nomads who have used the steppe for millennia, has experienced an average 1.7 degrees C temperature rise over the past 40 years. Continuing climate change is likely to affect flowering phenology and flower numbers with potentially important consequences for plant community composition, ecosystem services, and herder livelihoods. Over the growing seasons of 2009 and 2010, we examined flowering responses to climate manipulation using open-top passive warming chambers (OTCs) at two locations on a south-facing slope: one on the moister, cooler lower slope and the other on the drier, warmer upper slope, where a watering treatment was added in a factorial design with warming. Canonical analysis of principal coordinates (CAP) revealed that OTCs reduced flower production and delayed peak flowering in graminoids as a whole but only affected forbs on the upper slope, where peak flowering was also delayed. OTCs affected flowering phenology in seven of eight species, which were examined individually, either by altering the time of peak flowering and/or the onset and/or cessation of flowering, as revealed by survival analysis. In 2010, which was the drier year, OTCs reduced flower production in two grasses but increased production in an annual forb found only on the upper slope. The particular effects of OTCs on phenology, and whether they caused an extension or contraction of the flowering season, differed among species, and often depended on year, or slope, or watering treatment; however, a relatively strong pattern emerged for 2010 when four species showed a contraction of the flowering season in OTCs. Watering increased flower production in two species in 2010, but slope location more often affected flowering phenology than did watering. Our results show the importance of taking landscape-scale variation into account in climate change studies and also contrasted with those of several studies set in cold, but wetter systems, where warming often causes greater or accelerated flower production. In cold, water-limited systems like the Mongolian steppe, warming may reduce flower numbers or the length of the flowering season by adding to water stress more than it relieves cold stress.     

Contamination of Surface Soils, River Water and Sediments by Trace Metals from Copper Processing Industry in the Churnet River Valley, Staffordshire, UK

The impacts of a functional and a demolished copper processing works on the aquatic and terrestrial environment in the vicinity of the works was investigated by determining the levels of selected trace metals in river water, river sediments, channel margin sediments and overbank soils. Samples were taken at five sites within an area of the Churnet Valley in Staffordshire, where the River Churnet flows through the two works. Analysis of river water samples by Inductively Coupled Plasma-Mass Spectrometry (ICP-MS) has shown that only copper is present above background levels considered to typify uncontaminated rivers. Analysis of river sediments, channel margin sediments and overbank soils by nitric-perchloric acid digestion and Inductively Coupled Plasma-Atomic Emission Spectroscopy (ICP-AES) analysis has indicated contamination by arsenic, cadmium and copper in the vicinity of both works. Arsenic and copper are deposited primarily within the aquatic environment, although some contamination of the terrestrial environment by copper is also observed. Cadmium is deposited primarily within the terrestrial environment. The deposition of arsenic and copper in river and channel margin sediments respectively is also related to current and historical contamination.