Although macrophyte herbivore interactions in freshwater systems were generally disregarded for many years, recent data suggest that herbivory can be intense and important in structuring freshwater communities. This has led to the hypothesis that chemical defenses should be common among freshwater plants, but few studies have reported such chemical defenses, and no previous studies have assessed the frequency of chemical defenses among a substantial number of freshwater plant species. In a study of 21 macrophyte species co-occurring with the omnivorous crayfish Procambarus acutus in a southeastern USA wetland environment, we found that extracts of 11 species (52%) deterred feeding by P. acutus when tested in artificial foods at natural concentrations. Of these 11 chemically defended species, one species, Eupatorium capillifolium, consistently had a more unpalatable extract following mechanical damage to plant tissue, indicative of an activated chemical defense. Because herbivores are commonly nitrogen-limited and select food based on several plant traits, including plant nutritional value, it might be expected that chemical defenses would be especially important for protein-rich plants. However, we found no relationship between soluble protein concentration and deterrence of plant extracts.

Hundreds of millions of dollars have been spent on stream restoration projects to benefit salmonids and other aquatic species across the Pacific Northwest, though only a small percentage of these projects are monitored to evaluate effectiveness and far fewer are tracked for more than 1 or 2 years. The Washington State Salmon Recovery Board and the Oregon Watershed Enhancement Board have spent more than US$500 million on salmonid habitat restoration projects since 1999. We used a multiple before-after-control-impact design to programmatically evaluate the reach-scale physical and biological effectiveness of a subset of restoration actions. A total of 65 projects in six project categories (fish passage, instream habitat, riparian planting, livestock exclusion, floodplain enhancement, and habitat protection) were monitored over an 8-year period. We conducted habitat, fish, and macroinvertebrate surveys to calculate the following indicators: longitudinal pool cross section and depth, riparian shade and cover, large woody debris volumes, fish density, macroinvertebrate indices, and upland vegetation condition class. Results indicate that four categories (instream habitat, livestock exclusions, floodplain enhancements, and riparian plantings) have shown significant improvements in physical habitat after 5 years. Abundance of juvenile Coho Salmon Oncorhynchus kisutch increased significantly at fish passage projects and floodplain enhancement projects, but significant results were not detected for other fish species. Moreover, the biological response indicators of juvenile salmonid abundance and macroinvertebrate indices showed declines at instream habitat and habitat protection projects, respectively. Our results indicate that a subset of projects can be effectively evaluated programmatically, but power and sample size estimates indicate that two or more years of preproject data are necessary to adequately determine the effectiveness of many project types, particularly for fish. Programmatic evaluations of project effectiveness should include adequate preproject sampling and multiseason monitoring for fish species to address issues of variability that are likely to be encountered in large-scale monitoring programs.

Research Impact Statement: Hydraulic models are error-prone where rivers interact with large wood jams. Our method for representing wood jams improves hydraulic model accuracy and ecohydraulic analysis.ABSTRACT: Large wood (LW) jams are key riverine habitat features that affect hydraulic processes and aquatic habitat. The hydraulic influence of LW jams is poorly understood due to the complexity of fluid dynamics around irregular, porous structures. Here we validated a method for two-dimensional hydraulic modeling of porous LW jams using the open-source modeling software Delft3D-FLOW. We sampled 19 LW jams at three reaches across the Columbia River Basin in the United States. We used computer-generated porous plates to represent LW jams in the modeling software and calibrated our modeling method by comparing model outputs to measured depths and velocities at validation points. We found that modeling outputs are error-prone when LW jams are not represented. By representing LW jams as porous plates we reduced average velocity root mean square error (RMSE) values (i.e., improved model accuracy) by 42.8% and reduced average depth RMSE values by 5.2%. These differences impacted habitat suitability index modeling. We found a 15.1% increase in weighted useable area for juvenile steelhead at one test site when LW jams were simulated vs. when they were ignored. We investigated patterns in average RMSE improvements with varying jam size, bankfull obstruction, porosity, and structure type, and river complexity. We also identified research gaps related to field estimation of LW jam porosity and porous structure modeling methods.(KEYWORDS: rivers/streams; fluvial processes; 2D simulations; field measurements; large wood jam; hydraulic modeling; fish habitat suitability; river restoration.) Paper No. JAWRA-18-0166-P of the Journal of the American Water Resources Association (JAWRA).

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