Ryan A. McManamay

Does diet influence consumer nutrient cycling? Macroinvertebrate and fish excretion in streams

Abstract Consumer nutrient cycling supplies limiting elements to autotrophic and heterotrophic organisms in aquatic systems. However, the role of consumers in supplying nutrients may change depending on their diet and their own stoichiometry. We evaluated the stoichiometry, N and P excretion, and diets of the dominant macroinvertebrates and fish at 6 stream sites to determine if the nutritional composition of food alters nutrient excretion. We used Sterners (1990) nutrient homeostasis model as a reference to gauge whether consumer nutrient excretion is influenced by diet. Body stoichiometry explained 61% of the variation in N∶P excretion by macroinvertebrates but only 11% of the variation for fish. In both cases, the relationship was driven by 2 P-rich end-members, crayfish and mottled sculpin. Results of Akaike Information Criterion (AIC) analysis showed that family alone explained 71% of the variation in N∶P excretion in macroinvertebrates and 31% of the variation in fish. Diet explained only 8% of the variation in both cases. Most consumers (9 of 11) had N∶P excretion values that were well below predictions of Sterners model. Two taxa, crayfish and sculpin, had N∶P excretion that overlapped the models predictions. Our results suggest that crayfish and sculpin may display strict homeostasis with respect to N and P and that their growth might be P-limited. Other consumers may be more flexible in their stoichiometry and not P-limited. We speculate that the extremely low excretion N∶P measured for many consumers might have been the result of semiflexible homeostasis, inaccuracies in our assessment of dietary nutrients, growth-limiting nutrients other than N or P, or lack of egestion data. Our results suggest that crayfish and sculpin may alter N and P dynamics in streams by excreting low amounts of P relative to N compared to what is generally available in the water column.

Gravel Addition as a Habitat Restoration Technique for Tailwaters

Abstract We assessed the efficacy of passive gravel addition at forming catostomid spawning habitat under various flow regimes in the Cheoah River, a high-gradient tailwater river in North Carolina. The purpose was to provide a case study that included recommendations for future applications. A total of 76.3 m3 (162 tons) of washed gravel (10–50 mm) was passively dumped down the streambank and into the channel in four locations. Gravel sites differed in terms of average reach slope, bank slope, and the initial volume of gravel added, which could have influenced gravel entrainment. Maps of gravel movement under various flows suggested that large-magnitude discharges (≥113 m3/s) caused extensive migration; however, less obvious, smaller discharges (∼28 m3/s) still caused substantial shifting, which may influence the stability of catostomid spawning substrates. Following gravel addition, the proportion of gravel in the streambed was significantly higher at all gravel sites. However, comparisons of sites to r...

New Stream-reach Development: A Comprehensive Assessment of Hydropower Energy Potential in the United States

The rapid development of multiple national geospatial datasets related to topography, hydrology, and environmental characteristics in the past decade have provided new opportunities for the refinement of hydropower resource potential from undeveloped stream-reaches. Through 2011 to 2013, the Oak Ridge National Laboratory (ORNL) was tasked by the Department of Energy (DOE) Water Power Program to evaluate the new stream-reach development (NSD) resource potential for more than 3 million US streams. A methodology was designed that contains three main components: (1) identification of stream-reaches with high energy density, (2) topographical analysis of stream-reaches to estimate inundated surface area and reservoir storage, and (3) environmental attribution to spatially join information related to the natural ecological systems, social and cultural settings, policies, management, and legal constraints to stream-reaches of energy potential. An initial report on methodology (Hadjerioua et al., 2013) was later reviewed and revised based on the comments gathered from two peer review workshops. After implementing the assessment across the entire United States, major findings were summarized in this final report. The estimated NSD capacity and generation, including both higher-energy-density (>1 MW per reach) and lower-energy-density (<1 MW per reach) stream-reaches is 84.7 GW, around the same size as the existing USmorexa0» conventional hydropower nameplate capacity (79.5 GW; NHAAP, 2013). In terms of energy, the total undeveloped NSD generation is estimated to be 460 TWh/year, around 169% of average 2002 2011 net annual generation from existing conventional hydropower plants (272 TWh/year; EIA, 2013). Given the run-of-river assumption, NSD stream-reaches have higher capacity factors (53 71%), especially compared with conventional larger-storage peaking-operation projects that usually have capacity factors of around 30%. The highest potential is identified in the Pacific Northwest Region (32%), followed by Missouri Region (15%) and California Region (9%). In terms of states, the highest potential is found in Oregon, Washington, and Idaho, the three states in the Pacific Northwest, followed by California, Alaska, Montana, and Colorado. In addition to the resource potential, abundant environmental attributes were also organized and attributed to the identified stream-reaches to support further hydropower market analysis. The prevalence of environmental variables and proportion of capacity from stream-reaches intersecting environmental variables varied according to hydrologic region. Detailed NSD findings are organized by hydrologic regions and presented in each chapter of this report.«xa0less

Spawning of White Sucker (Catostomus commersoni) in a Stormwater Pond Inlet

Abstract In Apr. 2010 white suckers (Catostomus commersoni) were observed spawning in the small tributary to a constructed stormwater pond on the Virginia Polytechnic Institute and State University campus. The tributary is the only direct input to the pond and provides perennial flow. We documented spawning activity, habitat characteristics, habitat use, and verified spawning success based on egg fertilization, hatching, and larval drift. The water temperature, substrate, and gradient characteristics of this stream were similar to those reports for white sucker spawning sites elsewhere in unimpaired systems. This study demonstrates that white suckers can persist in what might be considered substandard stream habitat in an urbanizing environment. By extension, other freshwater fishes may find suitable habitats in such engineered ecosystems if ecological considerations are incorporated in the design phase of planning and construction.

Stream Classification Tool User Manual: For Use in Applications in Hydropower-Related Evironmental Mitigation

Stream classifications are an inventory of different types of streams. Classifications help us explore similarities and differences among different types of streams, make inferences regarding stream ecosystem behavior, and communicate the complexities of ecosystems. We developed a nested, layered, and spatially contiguous stream classification to characterize the biophysical settings of stream reaches within the Eastern United States (~ 900,000 reaches). The classification is composed of five natural characteristics (hydrology, temperature, size, confinement, and substrate) along with several disturbance regime layers, and each was selected because of their relevance to hydropower mitigation. We developed the classification at the stream reach level using the National Hydrography Dataset Plus Version 1 (1:100k scale). The stream classification is useful to environmental mitigation for hydropower dams in multiple ways. First, it creates efficiency in the regulatory process by creating an objective and data-rich means to address meaningful mitigation actions. Secondly, the SCT addresses data gaps as it quickly provides an inventory of hydrology, temperature, morphology, and ecological communities for the immediate project area, but also surrounding streams. This includes identifying potential reference streams as those that are proximate to the hydropower facility and fall within the same class. These streams can potentially be used tomorexa0» identify ideal environmental conditions or identify desired ecological communities. In doing so, the stream provides some context for how streams may function, respond to dam regulation, and an overview of specific mitigation needs. Herein, we describe the methodology in developing each stream classification layer and provide a tutorial to guide applications of the classification (and associated data) in regulatory settings, such as hydropower (re)licensing.«xa0less

Digital Mapping and Environmental Characterization of National Wild and Scenic River Systems

Spatially accurate geospatial information is required to support decision-making regarding sustainable future hydropower development. Under a memorandum of understanding among several federal agencies, a pilot study was conducted to map a subset of National Wild and Scenic Rivers (WSRs) at a higher resolution and provide a consistent methodology for mapping WSRs across the United States and across agency jurisdictions. A subset of rivers (segments falling under the jurisdiction of the National Park Service) were mapped at a high resolution using the National Hydrography Dataset (NHD). The spatial extent and representation of river segments mapped at NHD scale were compared with the prevailing geospatial coverage mapped at a coarser scale. Accurately digitized river segments were linked to environmental attribution datasets housed within the Oak Ridge National Laboratory s National Hydropower Asset Assessment Program database to characterize the environmental context of WSR segments. The results suggest that both the spatial scale of hydrography datasets and the adherence to written policy descriptions are critical to accurately mapping WSRs. The environmental characterization provided information to deduce generalized trends in either the uniqueness or the commonness of environmental variables associated with WSRs. Although WSRs occur in a wide range of human-modified landscapes, environmental data layers morexa0» suggest that they provide habitats important to terrestrial and aquatic organisms and recreation important to humans. Ultimately, the research findings herein suggest that there is a need for accurate, consistent, mapping of the National WSRs across the agencies responsible for administering each river. Geospatial applications examining potential landscape and energy development require accurate sources of information, such as data layers that portray realistic spatial representations. «xa0less