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Freshwater salinization is occurring around the world and impacting a wide variety of freshwater species that have evolved under low-salt conditions. Salt pollution reduces the survival of many freshwater taxa, but we know less about the effects of salt on individual traits. Moreover, we know even less about how salt pollution may affect phenotypically plastic traits that have evolved in response to natural stressors. In this study, we examined wood frog tadpoles (Rana sylvatica), which are a model system for predator-induced plasticity, and determined how their growth, behavior, and morphology changed in the presence of chemical cues from dragonflies (Anax junius) under four concentrations of NaCl (16, 250, 500, and 1000 mg Cl→/L). Early in the experiment, the tadpoles reduced their feeding activity in response to predator cues but did not respond to increasing salt concentrations. Tadpole mass increased with predator cues but decreased with increased salt concentrations. As expected, the predator cues induced relatively deeper tails and tail muscles, while inducing relatively shorter bodies and narrower mouths. However, we also discovered that salt induced relatively longer tails, longer bodies, and smaller eyes. Interestingly, the predator effects did not interact with salt effects for any of the traits. These results suggest that freshwater salinization has the potential to alter the traits of other freshwater species, but the effects may simply be additive. Future studies should examine salt-induced changes in a diversity of other freshwater species and investigate whether salt-induced changes in morphology have consequences to individual performance. 

Human activities are causing global change around the world including habitat destruction, invasive species in non-native ecosystems, overexploitation, pollution, and global climate change. While traditional monitoring has long been used to quantify and aid mitigation of global change,in-situautonomous sensors are being increasingly used for environmental monitoring. Sensors and sensor platforms that can be deployed in developed and remote areas and allow high-frequency data collection, which is critical for parameters that exhibit important short-term dynamics on the scale of days, hours, or minutes. In this article, we discuss the benefits ofin-situautonomous sensors in aquatic ecosystems as well as the many challenges that we have experienced over many years of working with these technologies. These challenges include decisions on sensor locations, sensor types, analytical specification, sensor calibration, sensor drift, the role of environmental conditions, sensor fouling, service intervals, cost of ownership, and data QA/QC. These challenges result in important tradeoffs when making decisions regarding which sensors to deploy, particularly when a network of sensors is desired to cover a large area. We also review recent advances in designing and building chemical-sensor platforms that are allowing researchers to develop the next-generation of autonomous sensors and the power of integrating multiple sensors into a network that provides increased insight into the dynamics of water quality over space and time. In the coming years, there will be an exponential growth in data related to aquatic sensing, which will be an essential part of global efforts to monitor and mitigate global change and its adverse impacts on society. 

Abstract The study of priority effects with respect to coinfections is still in its infancy. Moreover, existing coinfection studies typically focus on infection outcomes associated with exposure to distinct sets of parasite species, despite that functionally and morphologically similar parasite species commonly coexist in nature. Therefore, it is important to understand how interactions between similar parasites influence infection outcomes. Surveys at seven ponds in northwest Pennsylvania found that multiple species of echinostomes commonly co-occur. Using a larval anuran host ( Rana pipiens ) and the two most commonly identified echinostome species from our field surveys ( Echinostoma trivolvis and Echinoparyphium lineage 3), we examined how species composition and timing of exposure affect patterns of infection. When tadpoles were exposed to both parasites simultaneously, infection loads were higher than when exposed to Echinoparyphium alone but similar to being exposed to Echinostoma alone. When tadpoles were sequentially exposed to the parasite species, tadpoles first exposed to Echinoparyphium had 23% lower infection loads than tadpoles first exposed to Echinostoma . These findings demonstrate that exposure timing and order, even with similar parasites, can influence coinfection outcomes, and emphasize the importance of using molecular methods to identify parasites for ecological studies.