Reduction in labile copper in the 7-day Ceriodaphnia dubia toxicity test due to the interaction with zooplankton food

Due to the increased popularity of zooplankton toxicity tests, it is important to investigate potential confounding factors. Though zooplankton food has been studied extensively to meet the nutritional needs of the zooplankton, less research has been done on whether food addition reduces the toxicity of metals in the tested sample. This investigation combines toxicity tests and metal speciation analysis to determine whether the EPA recommended food of YCT (yeast, cerophyll, and trout chow) and Pseudokirchneriella subcapitata (formerly Selenastrum capricornutum) reduces copper toxicity by decreasing the concentration of labile copper. Toxicity tests were performed with Ceriodaphnia dubia on culture water spiked with 0, 787, and 1574 nM copper with five different food levels. A Chelex-100 cation exchange resin and a graphite furnace-atomic absorption spectrophotometer were used in conjunction with the toxicity tests to measure the amount of labile copper in the culture water. At the EPA recommended food dosage, the C. dubia food has a chelating capacity of approximately 500 nM Cu. For both concentrations of spiked culture water, the toxicity to C. dubia was reduced with increasing food level, which seemed to be both from a decrease in labile copper concentration and an increase in the nutritional condition of the zooplankton.     

Quantifying the importance of patch-specific changes in habitat to metapopulation viability of an endangered songbird

A growing number of programs seek to facilitate species conservation using incentive-based mechanisms. Recently, a market-based incentive program for the federally endangered Golden-cheeked Warbler (Dendroica chrysoparia) was implemented on a trial basis at Fort Hood, an Army training post in Texas, USA. Under this program, recovery credits accumulated by Fort Hood through contracts with private landowners are used to offset unintentional loss of breeding habitat of Golden-cheeked Warblers within the installation. Critical to successful implementation of such programs is the ability to value, in terms of changes to overall species viability, both habitat loss and habitat restoration or protection. In this study, we sought to answer two fundamental questions: Given the same amount of change in breeding habitat, does the change in some patches have a greater effect on metapopulation persistence than others? And if so, can characteristics of a patch (e.g., size or spatial location) be used to predict how the metapopulation will respond to these changes? To answer these questions, we describe an approach for using sensitivity analysis of a metapopulation projection model to predict how changes to specific habitat patches would affect species viability. We used a stochastic, discrete-time projection model based on stage-specific estimates of survival and fecundity, as well as various assumptions about dispersal among populations. To assess a particular patch's leverage, we quantified how much metapopulation viability was expected to change in response to changing the size of that patch. We then related original patch size and distance from the largest patch to each patch's leverage to determine if general patch characteristics could be used to develop guidelines for valuing changes to patches within a metapopulation. We found that both the characteristic that best predicted patch leverage and the magnitude of the relationship changed under different model scenarios. Thus, we were unable to find a consistent set of relationships, and therefore we emphasize the dangers in relying on general guidelines to assess patch value. Instead, we provide an approach that can be used to quantitatively evaluate patch value and identify critical needs for future research.     

Recycling in Jerusalem: right or privilege?

This study analyses disparities in the provision of environmental services in Jerusalem, specifically through the distribution of recycling bins. The allocation of recycling bins in Jerusalem is uneven. Some neighbourhoods have more than their share of infrastructure, while others do not have any recycling bins at all. The spatial distribution of recycling bins throughout the city is analysed across the ethno-religious and socioeconomic divides, enabling us to determine whether the opportunity to recycle is a right or a privilege. The findings demonstrate that the Arab areas are literally not serviced. Ultra-Orthodox (Haredi) Jewish neighbourhoods are discriminated against unless socioeconomic levels and population size are controlled. Therefore, waste-management policies reproduce social inequalities resulting in environmental injustice. Due to the fact that recycling in Jerusalem is voluntary and not obligatory, and that in general the public wants to recycle, the opportunity to recycle is indeed a privilege.