Fecal Indicator Bacteria Transport from Watersheds with Differing Wastewater Technologies and Septic System Densities

Wastewater contains elevated concentrations of fecal indicator bacteria (FIB). The type of wastewater treatment technology and septic system density may influence the FIB concentration and exports at the watershed scale. The goal of this study was to gain a better understanding of FIB concentrations and exports from watersheds served by conventional septic (CS) systems, sand filter (SF) septic systems, and a municipal sewer (SEW) system. Seven watersheds (3 CS, 3 SF, and 1 SEW) were monitored to quantify FIB concentration and export monthly from April 2015 to March 2016. The type of wastewater treatment did not yield significant differences in FIB concentration or exports when pooling watersheds using similar wastewater treatment. Watersheds with the highest septic densities (approximately 0.4 systems ha−1) contained greater FIB concentrations and exports than watersheds with the lowest (approximately 0.1–0.2 systems ha−1), but only FIB concentrations significantly differed. These findings suggest that when the septic system density exceeds 0.4 systems ha−1, water quality degradation from septic leachate may be observable at the watershed scale, especially in watersheds dominated by residential development. More research is recommended to determine if this density threshold is similar for other water pollutants and/or in watersheds with differing hydrogeological, land use, and wastewater characteristics

Posterior malformations in Dact1 mutant mice arise through misregulated Vangl2 at the primitive streak

Mice homozygous for mutations in Dact1 (Dpr/Frodo) phenocopy human malformations involving the spine, genitourinary system, and distal digestive tract. We trace this phenotype to disrupted germ layer morphogenesis at the primitive streak (PS). Remarkably, heterozygous mutation of Vangl2, a transmembrane component of the Planar Cell Polarity (PCP) pathway, rescues recessive Dact1 phenotypes, whereas loss of Dact1 reciprocally rescues semidominant Vangl2 phenotypes. We show that Dact1, an intracellular protein, forms a complex with Vangl2. In Dact1 mutants, Vangl2 is increased at the PS where cells ordinarily undergo an epithelial-mesenchymal transition. This is associated with abnormal E-cadherin distribution and changes in biochemical measures of the PCP pathway. We conclude that Dact1 contributes to morphogenesis at the PS by regulating Vangl2 upstream of cell adhesion and the PCP pathway

Modeling Recent Human Evolution in Mice by Expression of a Selected EDAR Variant

SummaryAn adaptive variant of the human Ectodysplasin receptor, EDARV370A, is one of the strongest candidates of recent positive selection from genome-wide scans. We have modeled EDAR370A in mice and characterized its phenotype and evolutionary origins in humans. Our computational analysis suggests the allele arose in central China approximately 30,000 years ago. Although EDAR370A has been associated with increased scalp hair thickness and changed tooth morphology in humans, its direct biological significance and potential adaptive role remain unclear. We generated a knockin mouse model and find that, as in humans, hair thickness is increased in EDAR370A mice. We identify new biological targets affected by the mutation, including mammary and eccrine glands. Building on these results, we find that EDAR370A is associated with an increased number of active eccrine glands in the Han Chinese. This interdisciplinary approach yields unique insight into the generation of adaptive variation among modern humans.PaperFlic

Long-term climate commitments projected with climate - carbon cycle models

Eight earth system models of intermediate complexity (EMICs) are used to project climate change commitments for the recent IPCC Fourth Assessment Report (IPCC AR4). Simulations are run until year 3000 AD and extend substantially further into the future than conceptually similar simulations with Atmosphere-Ocean General Circulation Models (AOGCMs) coupled to carbon cycle models. We investigate (1) the climate change commitment in response to stabilized greenhouse gases and radiative forcing, (2) the climate change commitment in response to earlier CO2 emissions, and (3) emission trajectories for profiles leading to stabilization of atmospheric CO2 and their uncertainties due to carbon cycle processes. Results over the 21st century compare reasonably well with results from AOGCMs and the suite of EMICs proves well suited to complement more complex models. We identify substantial climate change commitments for sea level rise and global mean surface temperature increase after a stabilization of atmospheric greenhouse gases and radiative forcing in year 2100. The additional warming by year 3000 is 0.6 to 1.6 K for the low-CO2 SRES B1 scenario and 1.3 to 2.2 K for the high-CO2 SRES A2 scenario. Correspondingly, the post-2100 thermal expansion commitment is 0.3 to 1.1 m for SRES B1 and 0.5 to 2.2 m for SRES A2. Sea level continues to rise due to thermal expansion for several centuries after CO2 stabilization.In contrast, surface temperature changes slow down after a century. The meridional overturning circulation is weakened in all EMICs, but recovers to nearly initial values in all but one of the models after centuries for the scenarios considered. Emissions during the 21st century continue to impact atmospheric CO2 andclimate even at year 3000. All models consistently find that most of the anthropogenic carbon emissions are eventually taken up by the ocean (49 to 62 %) in year 3000, and that a substantial fraction (15 to 28 %) is still airborne even after carbon emissions have ceased for 900 years. Future stabilization of atmospheric CO2 and climate change requires a substantial reduction of CO2 emissions below present levels in all EMICs. This reduction needs to be substantially larger if carbon cycle - climate feedbacks are accounted for or if terrestrial CO2 fertilization is not operating. We identify large differences among EMICs in both the response to increasing atmospheric CO2 and the response to climate change. This highlights the need for improved representations of carbon cycle processes in these models apart from the sensitivity to climate change. Sensitivity simulations with one single EMIC indicate that the impact of climate sensitivity related uncertainty on projected allowable emissions is substantially smaller than the uncertainty related to different carbon cycle settings