Development of Predictive Bioassessment Indices of Non-Perennial Streams and Rivers in the Arid Southwestern United States

Freshwater systems are a limited resource and must be managed to maintain or restore their ecological health. Bioassessments, which use the biota at a site to draw conclusions on a system’s ecological health, are commonly applied to freshwater systems. Freshwater bioassessment programs are typically only applicable in perennial systems (those which have surface water continually) and do not yet have an accepted role in assessing non-perennial streams in their dry phase. Although dry phase non-perennial streams that have a significant hydrological nexus with traditionally navigable waters navigable waters are protected under the state of California and national legislations, they cannot be assessed with bioassessment currently. We sampled 106 dry streams in the arid southwestern United States and developed indices of taxonomic completeness (i.e., Observed to Expected or O/E indices) in dry streams to assess the effect of anthropogenic stress at these sites. We did this for three key assemblages in dry streams: channel-dwelling arthropods, riparian vegetation-dwelling arthropods, and bryophytes. We also explored different definitions ways of identifying reference sites and parameters related to index development to assess their effects on O/E indices’ performance. O/E indices using channel arthropods were the most responsive and sensitive to human activity, regardless of which reference definition or probability of capture threshold was used. Channel arthropods were the most responsive likely because they respond in a predictable way to stress. Vegetation-dwelling arthropods and bryophytes were absent at up to one quarter of all sites, which negatively affected index performance. The absence of these assemblages at reference sites yielded less responsive and unsuccessful indices developed with these assemblages. The ecological status of dry streams can be determined from indices of taxonomic completeness when using channel-dwelling arthropods. Other taxa may not occur consistently enough across sites to produce responsive indices. Vegetation-dwelling arthropods should be omitted from future O/E studies because of their lack of response to stressors in stream channels. Further research should be conducted on moss and their response to local stressors because of their response to stress is difficult to predict

Behavior of lamellar forming block copolymers under nanoconfinement: implications for topography directed self-assembly of sub-10 nm structures

Directed self-assembly of block copolymers (BCPs) is a promising technique for the nanofabrication of structures with dimensions smaller than what can be achieved by current photolithography approaches. In particular, there has been significant interest in the development of BCPs that can achieve ever smaller feature sizes with low levels of defects. Here we investigate the directed self-assembly of a high-chi BCP, polystyrene-block-poly(in-lactide), which is capable of producing structures with dimensions less than 10 nm. In addition, we study the behavior of the BCP under nanoconfinement and the ability of the polymer chains to compress and stretch in response to the geometry of the confining volume. Key findings of this study are that the level of defects in the self-assembled structures are strongly related to the relative interfacial interactions of the BCP as well as the degree of frustration of the polymer chains under nanoconfinement relative to the bulk. These results have particular significance for nanofabrication of ordered structures, which is of relevance for the fabrication of nanowires, metamaterials, and next-generation computer chips

Community richness of amphibian skin bacteria correlates with bioclimate at the global scale

Animal-associated microbiomes are integral to host health, yet key biotic and abiotic factors that shape host-associated microbial communities at the global scale remain poorly understood. We investigated global patterns in amphibian skin bacterial communities, incorporating samples from 2,349 individuals representing 205 amphibian species across a broad biogeographic range. We analysed how biotic and abiotic factors correlate with skin microbial communities using multiple statistical approaches. Global amphibian skin bacterial richness was consistently correlated with temperature-associated factors. We found more diverse skin microbiomes in environments with colder winters and less stable thermal conditions compared with environments with warm winters and less annual temperature variation. We used bioinformatically predicted bacterial growth rates, dormancy genes and antibiotic synthesis genes, as well as inferred bacterial thermal growth optima to propose mechanistic hypotheses that may explain the observed patterns. We conclude that temporal and spatial characteristics of the host’s macro-environment mediate microbial diversity.National Science Foundation/[DEB-1146284]/NSF/Estados UnidosNational Science Foundation/[IOS-1121758]/NSF/Estados UnidosNational Science Foundation/[DEB-1310036]/NSF/Estados UnidosJohn Templeton Foundation/[]/JTF/Estados UnidosDeutsche Forschungsgemeinschaft/[]/DFG/AlemaniaDeutsche Forschungsgemeinschaft/[VE247/9-1]/DFG/AlemaniaCoordenação de Aperfeiçoamento de Pessoal de Nível Superior/[]/CAPES/BrasilFundação de Amparo à Pesquisa do Estado de São Paulo/[#2013/50741-7]/FAPESP/BrasilConselho Nacional de Desenvolvimento Científico e Tecnológico/[]/CNPq/BrasilSimons Foundation/[429440, WTW]//Estados UnidosDeutscher Akademischer Austauschdienst/[]/DAAD/AlemaniaUniversidad de Costa Rica/[801-B2-029]/UCR/Costa RicaMinisterio de Ciencia, Tecnología y Telecomunicaciones/[849-PINN-2015]/MICITT/Costa RicaNational Research Foundation of Korea/[2015R1D1A1A01057282]/NRF/Corea del SurUCR::Vicerrectoría de Investigación::Unidades de Investigación::Ciencias Básicas::Centro de Investigación en Biología Celular y Molecular (CIBCM)UCR::Vicerrectoría de Investigación::Unidades de Investigación::Ciencias Básicas::Centro de Investigación en Estructuras Microscópicas (CIEMIC