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Abstract:The Chobe River Basin (CRB), a sub-basin of the Upper Zambezi Basin shared by Namibia and Botswana, is a complex hydrologic system that lies at the center of the world's largest transfrontier conservation area. Despite its regional importance for livelihoods and biodiversity, its hydrology, controlled by the timing and relative contributions of water from two regional rivers, remains poorly understood. An increase in the magnitude of flooding in this region since 2009 has resulted in significant displacements of rural communities. We use an innovative approach that employs time-series of thermal imagery and station discharge data to model seasonal flooding patterns, identify the driving forces that control the magnitude of flooding and the high population density areas that are most at risk of high magnitude floods throughout the watershed. Spatio-temporal changes in surface inundation determined using NASA Moderate-resolution Imaging Spectroradiometer (MODIS) thermal imagery (2000)(2001)(2002)(2003)(2004)(2005)(2006)(2007)(2008)(2009)(2010)(2011)(2012)(2013)(2014)(2015) revealed that flooding extent in the CRB is extremely variable, ranging from 401 km 2 to 5779 km 2 over the last 15 years. A multiple regression model of lagged discharge of surface contributor basins and flooding extent in the CRB indicated that the best predictor of flooding in this region is the discharge of the Zambezi River 64 days prior to flooding. The seasonal floods have increased drastically in magnitude since 2008 causing large populations to be displaced. Over 46,000 people (53% of Zambezi Region population) are living in high magnitude flood risk areas, making the need for resettlement planning and mitigation strategies increasingly important.

Preserved color markings in Paleozoic fossils are rare and have been hypothesized to refl ect muscular attachment scars, diagenetic artifacts, or the altered remains of biochromes (organic pigments) or sclerochromes (structural colors) embedded in fossilized skeletal remains. More than 25 exceptionally well preserved phacopid trilobites with spotted patterns are described from the Middle Devonian of western and central New York State (USA). The small (~0.23 mm) circular markings appear either brown on a lighter cuticle, or white on a darker cuticle. Thin section, scanning electron microscope imaging, energy-dispersive X-ray spectroscopy, and wavelength-dispersive spectroscopy elemental analyses show spots to be microcrystalline low-Mg calcite spheres embedded within the primary layer of the cuticle below the prismatic layer. Surrounding exoskeleton (low-Mg calcite) exhibits coarser crystallinity, typical lamellar structures, pore canals, and possible organic matrix, as expected for relatively unaltered trilobite skeletons. Potential diagenetic mineralogies or microstructures were not observed, making diagenesis an unlikely explanation. Spot distribution, morphology, and position in exoskeleton rule out a relationship with sites of musculature attachment and/ or insertion. We suggest that spots represent original biologic structures manifested as either crystallographic or optical loci resulting in sclerochrome spots or possibly clear spots embedded in the cuticle that contrasted with a pigmented exoskeleton and may have served as windows to an underlying epidermis.

Core Ideas Nutrient concentrations are low at Big Creek relative to expected biological‐response thresholds. Nutrient concentrations at Big Creek are typical of streams draining watersheds with similar land use. Flow‐adjusted nutrient concentrations at Big Creek have not increased over the short‐term. Nutrient concentrations in streams increase as watershed land area in pasture and urban uses increases. Nutrient concentrations in several streams of the Boston and Ozark Mountains region of Arkansas, including the Buffalo National River and its tributaries, have garnered tremendous interest. In particular, Big Creek has been the center of attention within the Buffalo River watershed because of a permitted concentrated animal feeding operation (CAFO). The objectives of this paper were to put nutrient concentrations of Big Creek into the context of the stream nutrient and watershed land‐use relationship and develop a framework to evaluate regional land‐use impacts on regional water quality. Nutrient concentrations in streams draining the Boston and Ozark Mountains region were related to the intensity of watershed land use. Concentrations in Big Creek were similar to other watersheds in the ecoregion with similar land use, suggesting limited impact of the CAFO on Big Creek at the present time. However, this does not preclude future impacts, and longer‐term monitoring continues.