Featured Collection Introduction: Connectivity of Streams and Wetlands to Downstream Waters

Connectivity is a fundamental but highly dynamic property of watersheds. Variability in the types and degrees of aquatic ecosystem connectivity presents challenges for researchers and managers seeking to accurately quantify its effects on critical hydrologic, biogeochemical, and biological processes. However, protecting natural gradients of connectivity is key to protecting the range of ecosystem services that aquatic ecosystems provide. In this featured collection, we review the available evidence on connections and functions by which streams and wetlands affect the integrity of downstream waters such as large rivers, lakes, reservoirs, and estuaries. The reviews in this collection focus on the types of waters whose protections under the U.S. Clean Water Act have been called into question by U.S. Supreme Court cases. We synthesize 40+ years of research on longitudinal, lateral, and vertical fluxes of energy, material, and biota between aquatic ecosystems included within the Act's frame of reference. Many questions about the roles of streams and wetlands in sustaining downstream water integrity can be answered from currently available literature, and emerging research is rapidly closing data gaps with exciting new insights into aquatic connectivity and function at local, watershed, and regional scales. Synthesis of foundational and emerging research is needed to support science‐based efforts to provide safe, reliable sources of fresh water for present and future generations.     

Differing Modes of Biotic Connectivity within Freshwater Ecosystem Mosaics

We describe a collection of aquatic and wetland habitats in an inland landscape, and their occurrence within a terrestrial matrix, as a “freshwater ecosystem mosaic” (FEM). Aquatic and wetland habitats in any FEM can vary widely, from permanently ponded lakes, to ephemerally ponded wetlands, to groundwater‐fed springs, to flowing rivers and streams. The terrestrial matrix can also vary, including in its influence on flows of energy, materials, and organisms among ecosystems. Biota occurring in a specific region are adapted to the unique opportunities and challenges presented by spatial and temporal patterns of habitat types inherent to each FEM. To persist in any given landscape, most species move to recolonize habitats and maintain mixtures of genetic materials. Species also connect habitats through time if they possess needed morphological, physiological, or behavioral traits to persist in a habitat through periods of unfavorable environmental conditions. By examining key spatial and temporal patterns underlying FEMs, and species‐specific adaptations to these patterns, a better understanding of the structural and functional connectivity of a landscape can be obtained. Fully including aquatic, wetland, and terrestrial habitats in FEMs facilitates adoption of the next generation of individual‐based models that integrate the principles of population, community, and ecosystem ecology.     

Can public engagement democratize environmental policymaking in a resource-dependent state? Comparative case studies from Alberta,Canada

What factors shape the democratic potential of public consultation in environmental policymaking? Here, the motivations, purposes, designs, and outcomes of recent public engagement on land use planning, climate change policy, and water resource management in Alberta, Canada are reviewed in order to show how the power dynamics of the political and economic context shape the democratic potential of public and stakeholder consultations, especially where dominant resource interests are at stake. At the same time, political leadership, interactions between civil society actors and key design elements are shown to be important to democratization.     

Pathways for the oxidation of sarin in urban atmospheres

The nerve agent sarin has recently been deployed by terrorists in a major city. The molecule is volatile and made its way to many victims by passing as vapor through a highly reactive medium. Here we estimate rates and pathways for the removal of gas phase sarin from a generalized urban atmosphere. Only information from the open scientific literature is used. By structure reactivity comparisons with the organophosphorus pesticides, hydroxyl radical hydrogen abstraction may occur in as little as one hour. Decomposition of side chains after hydroxyl attack leads to organic oxygenates which preserve the phosphonofluoridate and so toxicity. The aqueous aerosol surface is contacted in minutes and offers access to a range of dissolved nucleophiles. Substitution displaces the fluoride leaving group, giving safe phosphoric acid analogs. Because of uncertainties in the electron distribution and in aqueous decay mechanisms, the time constants must be viewed as lower limits.     

Prey odor discrimination by ingestively naive coachwhip snakes(Masticophis flagellum)

Summary Ingestively naive hatchling coachwhip snakes(Masticophis flagellum) detected integumentary chemicals from several potential prey species and discriminated them from chemical stimuli from other animals and from distilled water, strongly suggesting a genetic basis for these abilities. The strongest responses were to lizard and snake stimuli, which form a major part of the diet. Variable responses to chemical cues from other taxa are discussed. Responses by coachwhip snakes to prey chemicals appear to be highly specific, as suggested by the stronger reaction to vomodors of sympatric than of allopatric lizard species. The highly developed use of chemical cues by the diurnal, visually oriented coachwhip snake emphasizes the general importance of chemical senses to predation by nonvenomous snakes, regardless of the involvement of vision.     

Latitudinal variation in top-down and bottom-up control of a salt marsh food web

The shrub Iva frutescens, which occupies the terrestrial border of U.S. Atlantic Coast salt marshes, supports a food web that varies strongly across latitude. We tested whether latitudinal variation in plant quality (higher at high latitudes), consumption by omnivores (a crab, present only at low latitudes), consumption by mesopredators (ladybugs, present at all latitudes), or the life history stage of an herbivorous beetle could explain continental-scale field patterns of herbivore density. In a mesocosm experiment, crabs exerted strong top-down control on herbivorous beetles, ladybugs exerted strong top-down control on aphids, and both predators benefited plants through trophic cascades. Latitude of plant origin had no effect on consumers. Herbivorous beetle density was greater if mesocosms were stocked with beetle adults rather than larvae, and aphid densities were reduced in the "adult beetle" treatment. Treatment combinations representing high and low latitudes produced patterns of herbivore density similar to those in the field. We conclude that latitudinal variation in plant quality is less important than latitudinal variation in top consumers and competition in mediating food web structure. Climate may also play a strong role in structuring high-latitude salt marshes by limiting the number of herbivore generations per growing season and causing high overwintering mortality.     

Physiological responses of the calcifying rhodophyte, <Emphasis Type="Italic">Corallina officinalis</Emphasis> (L.), to future CO<Subscript>2</Subscript> levels

Future atmospheric CO₂ levels will most likely have complex consequences for marine organisms, particulary photosynthetic calcifying organisms. Corallina officinalis L. is an erect calcifying macroalga found in the inter- and subtidal regions of temperate rocky coastlines and provides important substrate and refugia for marine meiofauna. The main goal of the current study was to determine the physiological responses of C. officinalis to increased CO₂ concentrations expected to occur within the next century and beyond. Our results show that growth and production of inorganic material decreased under high CO₂ levels, while carbonic anhydrase activity was stimulated and negatively correlated to algal inorganic content. Photosynthetic efficiency based on oxygen evolution was also negatively affected by increased CO₂. The results of this study indicate that C. officinalis may become less competitive under future CO₂ levels, which could result in structural changes in future temperate intertidal communities.