David C Walters

Chemical contamination of freshwaters is a global problem. In the United States alone, millions of kilometers of rivers and hectares of lakes and wetlands are impaired from contamination by chemicals including mercury, pesticides, polychlorinated biphenyls (PCBs), and trace metals (US Environmental Protection Agency, 2017). Efforts to mitigate the risks of contamination have largely...

Industrial chemical contamination within coastal regions of the Great Lakes can pose serious risks to wetland habitat and offshore fisheries, often resulting in fish consumption advisories that directly affect human and wildlife health. Mercury (Hg) is a contaminant of concern in many of these highly urbanized and industrialized coastal regions, one of which is the Saint Louis River...

Aquatic insects link food web dynamics across freshwater-terrestrial boundaries and subsidize terrestrial consumer populations. Contaminants that accumulate in larval aquatic insects and are retained across metamorphosis can increase dietary exposure for riparian insectivores. To better understand potential exposure of terrestrial insectivores to aquatically-derived trace metals, metal

Ecologists have long recognized that ecological subsidies (the flow of organic matter, nutrients, and organisms between ecosystems) can strongly affect ecosystem processes and community structure in the recipient ecosystem. Animal movements, organic matter flows, and food web dynamics between linked aquatic and terrestrial systems can also influence contaminant fate, exposure, and...

Insect-mediated contaminant flux is truly an interdisciplinary concept that merges ideas from many technical areas of science (e.g., environmental chemistry, landscape ecology, and entomology). This chapter introduces risk assessors to this emerging and ecologically relevant concept by distilling the main mechanisms that drive insect-mediated contaminant flux and integrating them...

In this chapter, we synthesize the state of the science regarding ecological subsidies and contaminants at the land-water interface and suggest research and management approaches for linked freshwater-terrestrial ecosystems. Specifically, we focus on movements of animals with complex life histories and the detrital inputs associated with animal and plant matter delivered to freshwaters...

Little is known about the underlying mechanisms governing the bioaccumulation of uranium (U) in aquatic insects. We experimentally parameterized conditional rate constants for aqueous U uptake, dietary U uptake, and U elimination for the aquatic baetid mayfly Neocloeon triangulifer. Results showed that this species accumulates U from both the surrounding water and diet, with waterborne...

Mercury (Hg) is a pervasive environmental pollutant and contaminant of concern for both people and wildlife that has been a focus of environmental remediation efforts for decades. A growing body of literature has motivated calls for revising Hg consumption advisories to co-consider selenium (Se) levels in seafood and implies that remediating aquatic ecosystems with ecosystem-scale Se...

Mercury (Hg) biomagnification in aquatic food webs is a global concern; yet, the ways species traits and interactions mediate these fluxes remain poorly understood. Few pathways dominated Hg flux in the Colorado River despite large spatial differences in food web complexity, and fluxes were mediated by one functional trait, predation resistance. New Zealand mudsnails are predator...

Selenium is highly elevated in Appalachian streams and stream organisms that receive alkaline mine drainage from mountaintop removal coal mining compared to unimpacted streams in the region. Adult aquatic insects can be important vectors of waterborne contaminants to riparian food webs, yet pathways of Se transport and exposure of riparian organisms are poorly characterized. We...

Spatial heterogeneity in environmental conditions can prolong food availability by desynchronizing the timing of ephemeral, high‐magnitude resource pulses. Spatial patterns of water temperature are highly variable among rivers as determined by both natural and anthropogenic features, but the influence of this variability on freshwater resource pulse phenology is poorly documented. We...

Ecosystems associated with rivers are intricately connected to their entire watershed. The river ecosystem includes the channel of active water flow, floodplain, and riparian and hyporheic zones. This ecosystem is shaped by interactions among the natural flow of water, sediments within the river and entering the river, and large wood regimes within the riparian zone. River integrity...