Electrokinetic Treatment of Sludge

Disposal of sludge has become a major issue in the pulp and paper industry because of the decreased space in landfills and the possibility of pollution from the sludge. By increasing the amount of solids in the sludge (dewatering), the sludge could be disposed of using less land or by incineration, composting, or other method. The dewatered sludge is easier to handle also because of its decreased volume. The method of dewatering which was used for the experiment was by electrokinetics. Electrokinetics is the technology of separating solids and liquids from suspensions of finely divided solids or colloidal particles using an electrical potential. Using four different power levels, a final solids level of 5.9% was reached and a decreased volume of almost 50%. This data showed that electrokinetics does have the potential to greatly reduce the volume of material which needs to be disposed of. It may also be able to increase the solids level to a higher level with further modification

Differential jumping performance in newly metamorphosed Blanchard\u27s cricket frogs, Acris blanchardi (Anura: Hylidae), from fish- and invertebrate-dominated ponds

Organisms that adopt phenotypically plastic anti-predator strategies during larval stages may incur fitness costs later in development. These costs are typically difficult to define in many species. The difficulty of identifying ecological trade-offs may result from experimental comparisons that do not adequately mirror naturally occurring predator-prey relatioships. To examine this, we captured 61 newly metamorphosed Acris blanchardi from ponds dominated either by fish or invertebrate predators. These predators are known to induce alternate phenotypic anti-predator responses at the larval stage. We use jumping performance as a measure of post-metamorphic fitness, and compared the morphological traits and jumping ability of frogs from ponds with and without fish. Frogs from fishless ponds can jump significantly farther than frogs from fish-dominated ponds. Morphological measurements indicated that overall frog size determined differences in jumping ability, with hind-leg length primarily explaining jumping performance. Differences in hind-leg length positively correlated with overall body size, which differed between the two types of ponds and did not result from allometric growth between them. Differences in frog sizes presumably are related to differences in developmental anti-predator morphologies in larvae

Effects of urbanization on the occurrence of Batrachochytrium dendrobatidis: do urban environments provide refuge from the amphibian chytrid fungus?

Batrachochytrium dendrobatidis (Bd) is a widespread pathogenic fungus that is known to cause the disease, chytridiomycosis, which can be lethal to many amphibians. We compared occurrence rates on spring peepers (Pseudacris crucifer) in urban and forested breeding sites in eastern Texas, USA. All study sites were at approximately the same latitude and altitude, and samples were collected at the same time of year to isolate differences in Bd infection rates between habitat types. We found significant differences (p\u3c0.001) in the occurrence of Bd between habitats; with dramatically lower rates of occurrence at urban sites (19.5 %), compared to forested sites (62.9 %). The exact reason for the observed differences in the occurrence of Bd is not known, however, we suspect that warmer temperatures or lower population densities and lower species richness at urban sites all could play a role in our results. Our findings suggest that urban environments may provide a refuge for some amphibians from the pathogen

Batrachochytrium dendrobatidis Detected in Amphibians from National Forests in Eastern Texas, USA

The amphibian disease chytridiomycosis, caused by the pathogenic fungus Batrachochytrium dendrobatidis (Bd, Longcore et al. 1999), is well known as a major threat to amphibians resulting in mass die-offs and population declines throughout the world (Berger et al. 1998; Blaustein and Keisecker 2002; Daszak et al. 2003; McCallum 2005; Rachowicz et al. 2006). Batrachochytrium dendrobatidis has been detected on amphibians from sites across North America (Ouellet et al. 2005; Woodhams et al. 2008) and appears to be most prevalent in the western and the northeastern United States (Longcore et al. 2007; Schlaepfer et al. 2007). Whereas infected anurans also have been found throughout the southeastern US (Green and Dodd 2007), there have been no reports of Bd from amphibians in eastern Texas, a broad area encompassing 10,000,000 ha. We sampled amphibians for the presence of Bd in four National Forests in eastern Texas (approximately 31°N latitude)

Effects of an Invasive Plant, Chinese Tallow (Triadica sebifera), on Development and Survival of Anuran Larvae

Amphibians are considered one of the most threatened vertebrate groups. Although numerous studies have addressed the many causes of amphibian population decline, little is known about effects of invasive plants. Chinese tallow (Triadica sebifera) is an exotic deciduous tree that has invaded the southeastern United States. Amphibian larvae in environments invaded by T. sebifera may be impacted negatively as autumn leaf litter decomposes in natal areas. We compared effects of leaf litter decomposition from T. sebifera and two native tree species on survival and development of four species of anuran larvae from eastern Texas. Larvae from Pseudacris fouquettei, Lithobates (Rana) sphenocephalus, Hyla versicolor, and Incilius (Bufo) nebulifer were introduced into mesocosms containing leaf litter from one of the three tree species. Pseudacris fouquettei and L. sphenocephalus, species that breed earlier in the year, had lower survival within the T. sebifera pools. Pseudacris fouquettei were smaller in T. sebifera mesocosms compared with native tree mesocosms, whereas L. sphenocephalus were larger in T. sebifera mesocosms. Hyla versicolor showed significant developmental and morphological differences in T. sebifera mesocosms; however, survival was not significantly different among treatments. Leaf litter treatment did not affect survival or development in I. nebulifer. Our results suggest that breeding season may determine how each species survives and develops in an environment with T. sebifera leaf litter. Triadica sebifera leaf litter breaks down faster than native species; therefore, negative effects may be short lived but pose a greater threat to species that breed soon after leaffall

Recovery from disturbance requires resynchronization of ecosystem nutrient cycles

Nitrogen (N) and phosphorus (P) are tightly cycled in most terrestrial ecosystems, with plant uptake more than 10 times higher than the rate of supply from deposition and weathering. This near-total dependence on recycled nutrients and the stoichiometric constraints on resource use by plants and microbes mean that the two cycles have to be synchronized such that the ratio of N:P in plant uptake, litterfall, and net mineralization are nearly the same. Disturbance can disrupt this synchronization if there is a disproportionate loss of one nutrient relative to the other. We model the resynchronization of N and P cycles following harvest of a northern hardwood forest. In our simulations, nutrient loss in the harvest is small relative to postharvest losses. The low N:P ratio of harvest residue results in a preferential release of P and retention of N. The P release is in excess of plant requirements and P is lost from the active ecosystem cycle through secondary mineral formation and leaching early in succession. Because external P inputs are small, the resynchronization of the N and P cycles later in succession is achieved by a commensurate loss of N. Through succession, the ecosystem undergoes alternating periods of N limitation, then P limitation, and eventually co-limitation as the two cycles resynchronize. However, our simulations indicate that the overall rate and extent of recovery is limited by P unless a mechanism exists either to prevent the P loss early in succession (e.g., P sequestration not stoichiometrically constrained by N) or to increase the P supply to the ecosystem later in succession (e.g., biologically enhanced weathering). Our model provides a heuristic perspective from which to assess the resynchronization among tightly cycled nutrients and the effect of that resynchronization on recovery of ecosystems from disturbance

Correlation of respiratory aerosols and metabolic carbon dioxide

Respiratory aerosols from breathing and talking are an important transmission route for viruses, including severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). Previous studies have found that particles with diameters ranging from 10 nm to 145 μm are produced from different regions in the respiratory system and especially smaller particles can remain airborne for long periods while carrying viral RNA. We present the first study in which respiratory aerosols have been simultaneously measured with carbon dioxide (CO2) to establish the correlation between the two concentrations. CO2 concentrations are easily available through low-cost sensors and could be used to estimate viral exposure through this correlation, whereas source-specific aerosol measurements are complicated and not possible with low-cost sensors. The increase in both respiratory aerosols and CO2 was linear over ten minutes in a 2 m3 chamber for all participants, suggesting a strong correlation. On average, talking released more particles than breathing, with 14,600 ± 16,800 min−1 (one-σ standard deviation) and 6210 ± 5630 min−1 on average, respectively, while CO2 increased with 139 ± 33 ppm min−1 during talking and 143 ± 29 ppm min−1 during breathing. Assuming a typical viral load of 7×106 RNA copies per mL of oral fluid, ten minutes of talking and breathing are estimated to produce 1 and 16 suspended RNA copies, respectively, correlating to a CO2 concentration of around 1800 ppm in a 2 m3 chamber. However, viral loads can vary by several orders of magnitude depending on the stage of the disease and the individual. It was therefore concluded that, by measuring CO2 concentrations, only the number and volume concentrations of released particles can be estimated with reasonable certainty, while the number of suspended RNA copies cannot

Evolutionary analyses of visual opsin genes in frogs and toads: Diversity, duplication, and positive selection

Among major vertebrate groups, anurans (frogs and toads) are understudied with regard to their visual systems, and little is known about variation among species that differ in ecology. We sampled North American anurans representing diverse evolutionary and life histories that likely possess visual systems adapted to meet different ecological needs. Using standard molecular techniques, visual opsin genes, which encode the protein component of visual pigments, were obtained from anuran retinas. Additionally, we extracted the visual opsins from publicly available genome and transcriptome assemblies, further increasing the phylogenetic and ecological diversity of our dataset to 33 species in total. We found that anurans consistently express four visual opsin genes (RH1, LWS, SWS1, and SWS2, but not RH2) even though reported photoreceptor complements vary widely among species. The proteins encoded by these genes showed considerable sequence variation among species, including at sites known to shift the spectral sensitivity of visual pigments in other vertebrates and had conserved substitutions that may be related to dim-light adaptation. Using molecular evolutionary analyses of selection (dN/dS) we found significant evidence for positive selection at a subset of sites in the dim-light rod opsin gene RH1 and the long wavelength sensitive cone opsin LWS. The function of sites inferred to be under positive selection are largely unknown, but a few are likely to affect spectral sensitivity and other visual pigment functions based on proximity to previously identified sites in other vertebrates. We also found the first evidence of visual opsin duplication in an amphibian with the duplication of the LWS gene in the African bullfrog, which had distinct LWS copies on the sex chromosomes suggesting the possibility of sex-specific visual adaptation. Taken together, our results indicate that ecological factors, such as habitat and life history, as well as behavior, may be driving changes to anuran visual systems

Road-Edge Effects on Herpetofauna in a Lowland Amazonian Rainforest

The impact of roads on the flora and fauna of Neotropical rainforest is perhaps the single biggest driver of habitat modification and population declines in these ecosystems. We investigated the road-edge effect of a low-use dirt road on amphibian and reptile abundance, diversity, and composition within adjacent lowland Amazonian rainforest at San José de Payamino, Ecuador. The road has been closed to vehicle traffic since its construction in 2010. Thus, effects from vehicle mortality, vehicle-related pollution, and road noise were not confounding factors. Herpetofauna were surveyed using both visual encounter surveys and drift fences with pitfall and funnel traps at varying distances from the road. Structural and microclimate features of the forest were measured at each sampling distance. Several habitat variables were found to differ at intermediate and interior sampling distances from the road compared to forest edge conditions, suggesting the road-edge effect began to attenuate by the intermediate sampling distance. However, the edge effect on amphibians and reptiles appeared to extend 100 m from the road edge, as abundance and diversity were significantly greater at the interior forest compared to the forest edge. Additionally, assemblage composition as well as the hierarchical position of species shifted between sampling distances. Habitat predictor models indicate that amphibian abundance was best predicted by vine abundance, while both vine and mature tree abundance were the best predictors for species richness and diversity. Overall, and contrary to what might otherwise be expected, our results demonstrate that small, little-used road disturbances can nonetheless have profound impacts on wildlife