J. Ryan Bellmore

Synthesis of common management concerns associated with dam removal

Managers make decisions regarding if and how to remove dams in spite of uncertainty surrounding physical and ecological responses, and stakeholders often raise concerns about certain negative effects, regardless of whether these concerns are warranted at a particular site. We used a dam-removal science database supplemented with other information sources to explore seven frequently raised concerns, herein Common Management Concerns (CMCs). We investigate the occurrence of these concerns and the contributing biophysical controls. The CMCs addressed are the following: degree and rate of reservoir sediment erosion, excessive channel incision upstream of reservoirs, downstream sediment aggradation, elevated downstream turbidity, drawdown impacts on local water infrastructure, colonization of reservoir sediments by nonnative plants, and expansion of invasive fish. Biophysical controls emerged for some of the concerns, providing managers with information to assess whether a given concern is likely to occur at a site. To fully assess CMC risk, managers should concurrently evaluate site conditions and identify the ecosystem or human uses that will be negatively affected if the biophysical phenomenon producing the CMC occurs. We show how many CMCs have one or more controls in common, facilitating the identification of multiple risks at a site, and demonstrate why CMC risks should be considered in the context of other factors such as natural watershed variability and disturbance history.

Incorporating food web dynamics into ecological restoration: a modeling approach for river ecosystems

Restoration is frequently aimed at the recovery of target species, but also influences the larger food web in which these species participate. Effects of restoration on this broader network of organisms can influence target species both directly and indirectly via changes in energy flow through food webs. To help incorporate these complexities into river restoration planning, we constructed a model that links river food web dynamics to in-stream physical habitat and riparian vegetation conditions. We present an application of the model to the Methow River, Washington, USA, a location of on-going restoration aimed at recovering salmon. Three restoration strategies were simulated: riparian vegetation restoration, nutrient augmentation via salmon carcass addition, and side channel reconnection. We also added populations of nonnative aquatic snails and fish to the modeled food web to explore how changes in food web structure mediate responses to restoration. Simulations suggest that side channel reconnection may be a better strategy than carcass addition and vegetation planting for improving conditions for salmon in this river segment. However, modeled responses were strongly sensitive to changes in the structure of the food web. The addition of nonnative snails and fish modified pathways of energy through the food web, which negated restoration improvements. This finding illustrates that forecasting responses to restoration may require accounting for the structure of food webs, and that changes in this structure, as might be expected with the spread of invasive species, could compromise restoration outcomes. Unlike habitat-based approaches to restoration assessment that focus on the direct effects of physical habitat conditions on single species of interest, our approach dynamically links the success of target organisms to the success of competitors, predators, and prey. By elucidating the direct and indirect pathways by which restoration affects target species, dynamic food web models can improve restoration planning by fostering a deeper understanding of system connectedness and dynamics.

Aquatic biodiversity in forests: a weak link in ecosystem services resilience

The diversity of aquatic ecosystems is being quickly reduced on many continents, warranting a closer examination of the consequences for ecological integrity and ecosystem services. Here we describe intermediate and final ecosystem services derived from aquatic biodiversity in forests. We include a summary of the factors framing the assembly of aquatic biodiversity in forests in natural systems and how they change with a variety of natural disturbances and human-derived stressors. We consider forested aquatic ecosystems as a multi-state portfolio, with diverse assemblages and life-history strategies occurring at local scales as a consequence of a mosaic of habitat conditions and past disturbances and stressors. Maintaining this multi-state portfolio of assemblages requires a broad perspective of ecosystem structure, various functions, services, and management implications relative to contemporary stressors. Because aquatic biodiversity provides multiple ecosystem services to forests, activities that compromise aquatic ecosystems and biodiversity could be an issue for maintaining forest ecosystem integrity. We illustrate these concepts with examples of aquatic biodiversity and ecosystem services in forests of northwestern North America, also known as Northeast Pacific Rim. Encouraging management planning at broad as well as local spatial scales to recognize multi-state ecosystem management goals has promise for maintaining valuable ecosystem services. Ultimately, integration of information from socio-ecological ecosystems will be needed to maintain ecosystem services derived directly and indirectly from forest aquatic biota.

Response of ecosystem metabolism to low densities of spawning Chinook Salmon

Marine derived nutrients delivered by large runs of returning salmon are thought to subsidize the in situ food resources that support juvenile salmon. In the Pacific Northwest, USA, salmon have declined to <10% of their historical abundance, with subsequent declines of marine derived nutrients once provided by large salmon runs. We explored whether low densities (<0.001 spawners/m2) of naturally spawning Chinook Salmon (Oncorhynchus tshawytscha) can affect ecosystem metabolism. We measured gross primary production (GPP) and ecosystem respiration (ER) continuously before, during, and after salmon spawning. We compared downstream reaches with low densities of spawning salmon to upstream reaches with fewer or no spawners in 3 mid-sized (4th-order) rivers in northern Washington. In addition, we measured chemical, physical, and biological factors that may be important in controlling rates of GPP and ER. We observed that low densities of spawning salmon can increase GPP by 46% during spawning, but values quickly return to those observed before spawning. No difference in ER was observed between up- and downstream reaches. Based on our results, salmon density, temperature, and the proximity to salmon redds were the most important factors controlling rates of GPP, whereas temperature was most important for ER. These results suggest that even at low spawning densities, salmon can stimulate basal resources that may propagate up the food web. Understanding how recipient ecosystems respond to low levels of marine derived nutrients may inform nutrient augmentation studies aimed at enhancing fish populations.