River restoration projects are increasingly common, but assessments of ecological responses and overall success of the vast majority of efforts are lacking. Information on potential positive ecological effects of restoration efforts can be used to justify further projects and refine methods. We examined responses of multiple trophic levels, aquatic insects and riparian birds, to a series of rock weirs installed in an Illinois river to stabilize the channel. We quantified adult insect emergence and performed weekly point counts of birds in spring at four weir and four nonweir (control) sites. Emerging insect abundance was higher at control sites, but species richness and diversity were higher at weir sites. Total insect emergence production did not differ between site types, but emergence production of larger-bodied taxa was higher at weir sites. Ordinations and analysis of similarity indicated differences in insect and bird assemblages between site types. Birds showed a positive numerical response to large-bodied emerging insects, and total bird abundance was higher at weir sites. Clutch size and feeding rates of a focal bird species, Prothonotaria citrea (Prothonotary Warbler), did not differ between sites, but the number of hatchlings and fledglings was higher at control sites. Molothrus ater (cowbird) parasitism was higher at weir sites, likely because of increased edge habitat associated with weir construction activities. Results show positive ecological impacts of in-stream restoration and provide justification for further efforts. However, forest disturbance associated with construction could offset some benefits to some species, and thus refinements to procedures may be necessary.

Multiple invasive species may interact, influencing one another and generating synergistic effects on food webs and ecosystem processes. We investigated the interaction between two non‐native species widespread in the western USA: common carp (Cyprinus carpio) and Russian olive (Elaeagnus angustifolia), an invasive riparian tree associated with di‐nitrogen fixation. Deep Creek, Idaho, was an International Biological Program site in the early 1970s; at that time, carp were rare and Russian olive was absent. Subsequently, Russian olive was introduced and established a dense stand, increasing allochthonous inputs and nitrogen‐rich benthic organic matter. Since 1971, carp density has increased ~4× (an increase our bioenergetic analysis suggests could not have been sustained in the absence of Russian olive). Carp gut contents in 2013–2014 revealed, on average, ~40% olives, and, similarly, stable isotope analyses revealed ~58% of carp tissues were derived from olives. A small‐scale, short‐term experimental exclusion of these subsidized carp caused ~3× increases in macrophytes and chlorophyll‐a, suggesting they may limit algae and macrophyte biomass. Moreover, carp that consumed olives excreted more nitrogen (~2× more ammonium, ~2× more total dissolved nitrogen, and ~3× more total nitrogen) compared to those that had not, which may amplify recycling and export from streams invaded by both species. This scenario is characteristic of an “invasional meltdown,” with attendant changes in food webs and ecosystem processes.

No abstract

Traditionally, exploration of ecosystems in the context of undergraduate education has been restricted to connections within conventionally defined habitats (i.e., within a stream, within a forest). Further, instruction regarding the aquatic-terrestrial interface has emphasized directional inputs from land to water. However, a relatively new body of research has characterized reciprocal interactions and draws attention to fluxes from water to land, including the emergence of aquatic insects that serve as prey for terrestrial predators. We present a guide to an inquiry-based lesson for undergraduate biology that explores interactions and connections across aquatic and terrestrial habitat boundaries. The focus is on cross-habitat linkages within ecosystems, specifically addressing the question, What is the role of insect emergence in connecting the web of life linking aquatic and terrestrial habitats and organisms? Students (1) engage with a documentary film, (2) explore insect emergence and make observations of riparian insectivores, (3) explain the collected data, (4) elaborate on alternative study designs and a measure of ecosystem health, and (5) evaluate their new understanding. This lesson addresses core concepts and competencies for undergraduate biology education, as identified in the Vision and Change report.