Six Principles for Embracing Gender and Sexual Diversity in Postsecondary Biology Classrooms.

Sexual and gender minorities face considerable inequities in society, including in science. In biology, course content provides opportunities to challenge harmful preconceptions about what is "natural" while avoiding the notion that anything found in nature is inherently good (the appeal-to-nature fallacy). We provide six principles for instructors to teach sex- and gender-related topics in postsecondary biology in a more inclusive and accurate manner: highlighting biological diversity early, presenting the social and historical context of science, using inclusive language, teaching the iterative process of science, presenting students with a diversity of role models, and developing a classroom culture of respect and inclusion. To illustrate these six principles, we review the many definitions of sex and demonstrate applying the principles to three example topics: sexual reproduction, sex determination or differentiation, and sexual selection. These principles provide a tangible starting place to create more scientifically accurate, engaging, and inclusive classrooms.

Cross-scale controls on the in-stream dynamics of nitrate and turbidity in semiarid agricultural waterway networks.

Stream and riparian zone networks embedded in agricultural landscapes provide a potential intervention point to ameliorate the negative effects of agricultural runoff by reducing transport of nitrate (NO3-) and suspended sediments (SS) downstream. However, our ability to support and promote NO3- and SS attenuation is limited by our understanding of vegetative and hydrogeomorphic controls in realistic management contexts. In addition, agricultural landscapes are heterogenous on multiple management scales, from farm field to regional water management scales, and the effect of these heterogeneities and how they interact across scales to affect vegetative and hydrogeomorphic controls is poorly explored in many settings. This is especially true in irrigated agricultural settings, where stream and riparian networks are entwined with and sensitive to water management systems. To fill these gaps, we related the vegetative and hydrogeomorphic features of 67 waterway reaches across two water management districts in the California Central Valley to reach-scale NO3- and turbidity attenuation and district-scale water quality patterns. We found that in-stream NO3- attenuation was rare, but, when it did occur, it was promoted by shallow and wide riparian banks, low flows, and high channel-edge denitrification potential. Nitrate concentrations were consistently higher in upstream reaches compared to water district outlets, suggesting that while exports from the district were low, agricultural runoff may impair within-district water resources. Turbidity attenuation was highly variable and unrelated to vegetative or hydrogeomorphic features, suggesting that onfield controls are crucial to managing suspended sediments. We conclude that waterway networks have the potential to mitigate the effects of agricultural NO3- runoff in this setting, but that more effective monitoring and adoption of NO3- attenuating features is needed. Using our findings, we make specific management and monitoring recommendations at both reach and water district scales.

Controls on denitrification potential in nitrate-rich waterways and riparian zones of an irrigated agricultural setting.

Denitrification, the microbial conversion of NO3- to N gases, is an important process contributing to whether lotic and riparian ecosystems act as sinks for excess NO3- from agricultural activities. Though agricultural waterways and riparian zones have been a focus of denitrification research for decades, almost none of this research has occurred in the irrigated agricultural settings of arid and semiarid climates. In this study, we conducted a broad survey of denitrification potential in riparian soils and channel sediments from 79 waterway reaches in the irrigated agricultural landscape of California's Central Valley. With this approach, we sought to capture the wide range of variation that arose from diverse waterway management and fluctuating flow conditions, and use this variation to identify promising management interventions. We explored associations of denitrification potentials with surface water NO3- -N, organic matter, flow conditions, vegetation cover, near-channel riparian bank slope, and channel geomorphic features using generalized linear mixed models. We found strong associations of sediment denitrification potentials with reach flow conditions, which we hypothesize was the result of variation in microbial communities' tolerance to dry-wet cycles. Denitrification potentials in riparian soils, in contrast, did not appear affected by flow conditions, but instead were associated with organic matter, vegetation cover, and bank slope in the riparian zone. These results suggest a strong need for further work on how denitrification responds to varying flow conditions and dry-wet cycles in non-perennial lotic ecosystems. Our findings also demonstrate that denitrifier communities respond to key features of waterway management, which can therefore be leveraged to control denitrification through a variety of management actions.