Emma J Rosi

• PhD University of Georgia
• Professor (Associate) at Cary Institute of Ecosystem Studies

Aquatic ecosystems are subjected to many chemical stressors, including nutrients and emerging contaminants like pharmaceuticals. While pharmaceutical concentrations in streams and rivers are often below the thresholds for acute toxicity, they nonetheless disrupt ecology through changes to organisms' physiology, metabolism, and behavior. However, an...

Recent observations document increased abundance of algae in the headwater streams of Hubbard Brook Experimental Forest (HBEF). It is possible that this “greening up” of HBEF streams may be due to climate change, with rising temperatures, altering terrestrial phenology, and shifting hydrologic regimes. Alternatively, stream “greening” could be from...

The lines between natural areas and human habitats have blurred as urbanization continues, creating a need for the study of ecosystems at all levels of development. This need is particularly acute for exurban environments, which have low population density but are rapidly changing and have a dynamic mix of natural and human-dominated features. We e...

The relationship between (a) the structure and composition of the landscape around an individual's home and (b) environmental perceptions and health outcomes has been well demonstrated (eg the value of vegetation cover to well‐being). Few studies, however, have examined how multiple landscape features (eg vegetation and water cover) relate to perce...

Novel viral pathogens are causing diseases to emerge in humans, a challenge to which society has responded with technological innovations such as antiviral therapies. Antivirals can be rapidly deployed to mitigate severe disease, and with vaccines, save human lives and provide a long-term safety net against new viral diseases. Yet with these advanc...

Sewage released from lakeside development can reshape ecological communities. Nearshore periphyton can rapidly assimilate sewage‐associated nutrients, leading to increases of filamentous algal abundance, thus altering both food abundance and quality for grazers. In Lake Baikal, a large, ultra‐oligotrophic, remote lake in Siberia, filamentous algal...

As rates of urbanization and climatic change soar, decision-makers are increasingly challenged to provide innovative solutions that simultaneously address climate-change impacts and risks and inclusively ensure quality of life for urban residents. Cities have turned to nature-based solutions to help address these challenges. Nature-based solutions,...

The lines between natural areas and human habitats have blurred as urbanization continues, creating a need for the study of ecosystems at all levels of development. This need is particularly acute for exurban environments, which have low population density but are rapidly changing and have a dynamic mix of natural and human-dominated features. We e...

Given the large and increasing amount of urban, suburban, and exurban land use on Earth, there is a need to accurately assess net primary productivity (NPP) of urban ecosystems. However, the heterogeneous and dynamic urban mosaic presents challenges to the measurement of NPP, creating landscapes that may appear more similar to a savanna than to the...

All animals carry specialized microbiomes, and their gut microbiota are continuously released into the environment through excretion of waste. Here we propose the meta-gut as a novel conceptual framework that addresses the ability of the gut microbiome released from an animal to function outside the host and alter biogeochemical processes mediated...

Animals can impact freshwater ecosystem structure and function in ways that persist well beyond the animal’s active presence. These legacy effects can last for months, even decades, and often increase spatial and temporal heterogeneity within a system. Herein, we review examples of structural, biogeochemical, and trophic legacies from animals in st...

Abstract Pharmaceuticals are ubiquitous in aquatic environments, yet little is known regarding their impacts on ecological processes. Selective serotonin reuptake inhibitors (SSRIs) are frequently prescribed human antidepressants and have been shown to alter crayfish behavior. These behavioral alterations are particularly relevant as crayfish play...

Urbanization increases stormwater runoff into streams, resulting in channel erosion, and increases in sediment and nutrient delivery to receiving water bodies. Stream restoration is widely used as a Best Management Practice to stabilize banks and reduce sediment and nutrient loads. While most instream nutrient retention measurements are often limit...

All animals carry specialized microbiomes, and their gut microbiotas in particular are continuously released into the environment through excretion of waste. Here we propose the meta-gut as a novel conceptual framework that addresses the ability of the gut microbiome released from an animal to function outside the host and potentially alter ecosyst...

Large wood (LW) additions are commonly used to restore degraded streams, particularly in regenerating forests that have low LW recruitment due to past logging. While the short‐term effects of LW input on stream structure and function are well studied, the long‐term dynamics of added wood are less documented. We assessed the long‐term movement and c...

Environmental proteins (eProteins), such as Cry proteins associated with genetically engineered (GE) organisms, are present in ecosystems worldwide, but only rarely reach concentrations with detectable ecosystem-level impacts. Despite their ubiquity, the degradation and fate of Cry and other eProteins are mostly unknown. Here, we report the results...

Hippopotami (hippos) are ecosystem engineers that subsidize aquatic ecosystems through the transfer of organic matter and nutrients from their terrestrial grazing, with potentially profound effects on aquatic biogeochemistry. We examined the influence of hippo subsidies on biogeochemical cycling in pools of varying hydrology and intensity of hippo...

Lotic and lentic ecosystems are traditionally viewed as dominated by either benthic or water column processes. However, mid-sized rivers represent a transition zone where both benthic and water column processes may both contribute substantially to ecosystem dynamics. Ecosystem processes such as gross primary production (GPP), ecosystem respiration...

Scavengers play an important role in nutrient recycling and disease control, and this role may be particularly critical after mass mortality events, such as those caused by epidemics, culling, or natural disasters. Current work on scavenger ecology has focused on use of single carcasses, but behaviors are likely to be different at mass mortality ev...

Nitrogen (N) limits primary production over large areas of the earth and has a particularly complex and interesting series of biological transformations in its cycle. Human manipulation of the N cycle is intense, as large amounts of “reactive” N are needed for crop production and are produced as a by-product of fossil fuel combustion. This manipula...

This chapter describes the various ways that pharmaceuticals, personal care products, and microplastics are released into freshwater ecosystems and explores the ecological effects of these novel pollutants. The occurrence of pharmaceuticals, personal care products, and microplastics in freshwater ecosystems spans the globe and reflects release from...

The Hubbard Brook Experimental Forest (HBEF) was established in 1955 by the U.S. Department of Agriculture, Forest Service out of concerns about the effects of logging increasing flooding and erosion. To address this issue, within the HBEF hydrological and micrometeorological monitoring was initiated in small watersheds designated for harvesting ex...

Stream solute monitoring has produced many insights into ecosystem and Earth system functions. Although new sensors have provided novel information about the fine‐scale temporal variation of some stream water solutes, we lack adequate sensor technology to gain the same insights for many other solutes. We used two machine learning algorithms – Suppo...

Large storage dams have widely documented impacts on downstream aquatic environments, but hydroelectric dams with little or no capacity for storage of water inflows (i.e., run-of-river) have received less attention. Two of the world’s largest run-of-river hydropower dams (Jirau and Santo Antônio, Brazil) are located on the Madeira River, the larges...

Pathogens and parasites (henceforth “pathogens”) can make up a large percentage of the biomass found in ecosystems, and therefore, their impacts on ecosystem processes should be prominent. Pathogens influence ecosystem processes by affecting the abundance or phenotype of hosts and through direct contributions to ecosystem production. However, there...

Headwaters suffer from reduced leaf and wood inputs and retention capacity from historical land actions like watershed logging and agriculture. When in-stream wood is reduced, stream retention capacity declines and subsequent changes in streamwater flow-paths and patterns of deposition alter decomposition and primary production that influence secon...

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. Ne...

The Earth's population will become more than 80% urban during this century. This threshold is often regarded as sufficient justification for pursuing urban ecology. However, pursuit has primarily focused on building empirical richness, and urban ecology theory is rarely discussed. The Baltimore Ecosystem Study (BES) has been grounded in theory sinc...

Animal carcasses can provide important resources for a suite of consumers, and bones may provide a largely overlooked component of this resource, as they contain a large proportion of the phosphorus (P) in a carcass and they can persist for decades to millennia. We synthesized several datasets from our research in the Mara River, in which annual ma...

Run-of-river dams are often considered to have lower environmental impacts than storage dams due to their smaller reservoirs and low potential for flow alteration. However, this has been questioned for projects recently built on large rivers around the world. Two of the world’s largest run-of-river dams—Santo Antônio and Jirau—were recently constru...

Diel variability in nutrient concentrations is common but not universal in aquatic ecosystems. Theoretical models of photoautotrophic systems attribute the absence of diel uptake variation to nutrient scarcity, such that diel variability in nutrient uptake disappears as nutrients become limiting. We tested this prediction in a mesocosm experiment,...

The continually increasing global population residing in urban landscapes impacts numerous ecosystem functions and services provided by urban streams. Urban stream restoration is often employed to offset these impacts and conserve or enhance the various functions and services these streams provide. Despite the assumption that “if you build it, [the...

Fluoxetine, a selective serotonin reuptake inhibitor (SSRI), is frequently detected in surface waters globally, yet the effects of SSRIs on ecological processes at environmentally realistic concentrations are not currently known. We used a controlled, replicated artificial stream experiment to expose biofilm, algal and stream insect communities to...

The majority of maize planted in the US is genetically-engineered to express insecticidal properties, including Cry1Ab protein, which is designed to resist the European maize borer (Ostrinia nubilalis). After crop harvest, these proteins can be leached into adjacent streams from crop detritus left on fields. The environmental fate of Cry1Ab protein...

While the importance of grasslands in terrestrial silicon (Si) cycling and fluxes to rivers is established, the influence of large grazers has not been considered. Here, we show that hippopotamuses are key actors in the savannah biogeochemical Si cycle. Through a detailed analysis of Si concentrations and stable isotope compositions in multiple eco...

The Mara River basin is a trans-boundary basin of international importance. It forms the headwaters of the Nile River and serves as the primary dry season water source for an estimated 1.1 million rural people and the largest remaining overland migration of 1.4 million wildebeest in the Serengeti-Mara Ecosystem. Changes throughout the basin are imp...

A multitude of biologically active pharmaceuticals contaminate surface waters globally, yet their presence in aquatic food webs remain largely unknown. Here, we show that over 60 pharmaceutical compounds can be detected in aquatic invertebrates and riparian spiders in six streams near Melbourne, Australia. Similar concentrations in aquatic inverteb...

In the face of mosquito-borne disease outbreaks, effective mosquito control is a primary goal for public health. Insect repellents, containing active compounds such as DEET and picaridin, are a first defence against biting insects. Owing to widespread use and incomplete sewage treatment, these compounds are frequently detected in surface waters, bu...

In many temperate forested watersheds, hydrologic nitrogen export has declined substantially in recent decades, and many of these watersheds show enduring effects from historic acid deposition. A watershed acid remediation experiment in New Hampshire, U.S.A. reversed many of these legacy effects of acid deposition and also increased watershed nitro...

• Understanding the mechanisms that control gross primary production (GPP) and ecosystem respiration (ER) is important in open‐canopy streams, particularly as their prevalence increases across the landscape with the expansion of human land use. • We measured resazurin (raz) transformation to resorufin (rru) as an indicator of ER in two contrasting...

Animals can be important vectors for the movement of resources across ecosystem boundaries. Animals add resources to ecosystems primarily through egestion, excretion and carcasses, and the stoichiometry and bioavailability of these inputs likely interacts with characteristics of the recipient ecosystem to determine their effects on ecosystem functi...

Non‐native species are among the most important drivers of the structure and function of modern ecosystems. The ecological impacts of a non‐native species ought to depend on the size and characteristics of its population, but the exact nature of this population‐impacts relationship is rarely defined. Both the mathematical form of this relationship...

The steadily rising global urban population has placed substantial strain on urban water quality, and this strain is projected to increase for the foreseeable future. Considerable attention has been given to the hydrological and physico‐chemical effects of urbanization on stream ecosystems. However, due to the relative infancy of the field of urban...

The application of environmental DNA (eDNA) to infer species presence in aquatic ecosystems has become an invaluable tool for both the ecology and management of aquatic ecosystems. However, we are only beginning to understand how environmental conditions influence eDNA detection and persistence in freshwaters. Here, we examined the degradation dyna...

Organic matter and nutrient loading into aquatic ecosystems affects ecosystem structure and function and can result in eutrophication and hypoxia. Hypoxia is often attributed to anthropogenic pollution and is not common in unpolluted rivers. Here we show that organic matter loading from hippopotami causes the repeated occurrence of hypoxia in the M...

Extreme events are of interest worldwide given their potential for substantial impacts on social, ecological, and technical systems. Many climate-related extreme events are increasing in frequency and/or magnitude due to anthropogenic climate change, and there is increased potential for impacts due to the location of urbanization and the expansion...

The Mara River Basin in East Africa is a trans-boundary basin of international significance experiencing excessive levels of sediment loads. Sediment levels in this river are extremely high (turbidities as high as 6,000 NTU) and appear to be increasing over time. Large wildlife populations, unregulated livestock grazing, and agricultural land conve...

Residues of pharmaceuticals are increasingly detected in surface waters throughout the world. In four streams in Baltimore, Maryland, USA, we detected analgesics, stimulants, antihistamines, and antibiotics using passive organic samplers. We exposed biofilm communities in these streams to the common drugs caffeine, cimetidine, ciprofloxacin, and di...

In this chapter, we describe nutrient limitation in stream ecosystems, the problems associated with elevated nutrient loading caused by human activities in the watershed, and how streams process and transform nutrients prior to downstream export. We provide a basic method for quantifying nutrient limitation of stream biofilms using nutrient diffusi...

Human activities create threats that have consequences for freshwater ecosystems and, in most watersheds, observed ecological responses are the result of complex interactions among multiple threats and their associated ecological alterations. Here we discuss the value of considering multiple threats in research and management, offer suggestions for...

Studies of trophic-level material and energy transfers are central to ecology. The use of isotopic tracers has now made it possible to measure trophic transfer efficiencies of important nutrients and to better understand how these materials move through food webs. We analyzed data from thirteen (15) N-ammonium tracer addition experiments to quantif...

Headwater streams remove, transform, and store inorganic nitrogen (N) delivered from surrounding watersheds, but excessive N inputs from human activity can saturate removal capacity. Most research has focused on quantifying N removal from the water column over short periods and in individual reaches, and these ecosystem-scale measurements suggest t...

A disturbance or natural event in forested streams that alter available light can have potential consequences for nutrient dynamics and primary producers in streams. In this study, we address how functional processes (primary production and nutrient uptake) in stream ecosystems respond to changes in forest canopy structure. We focus on differences...

The insecticidal Cry1Ab protein expressed by transgenic (Bt) maize can enter adjacent water bodies via multiple pathways, but its fate in stream ecosystems is not as well studied as in terrestrial systems. In this study, we used a combination of field sampling and laboratory experiments to examine the occurrence, leaching, and degradation of solubl...

Significance Much research has focused on the influence of animal migrations on terrestrial ecosystems. Mass drownings are an understudied phenomenon associated with migrations that may have substantial impacts on aquatic ecosystems. Here, we show that mass drownings of wildebeest occur nearly annually during the Serengeti wildebeest migration, and...

Urban streams are exposed to multiple different stressors on a regular basis, with increased hydrological flashiness representing a common urban stream stressor. Stream metabolism, the coupled ecosystem functions of gross primary production (GPP) and ecosystem respiration (ER), controls numerous other ecosystem functions and integrates multiple pro...

Ecosystem scientists will increasingly be called on to inform forecasts and define uncertainty about how changing planet conditions affect human well-being. We should be prepared to leverage the best tools available, including big data. Use of the term ‘big data’ implies an approach that includes capacity to aggregate, search, cross-reference, and...

Though concerns about the proliferation of synthetic chemicals - including pesticides - gave rise to the modern environmental movement in the early 1960s, synthetic chemical pollution has not been included in most analyses of global change. We examined the rate of change in the production and variety of pesticides, pharmaceuticals, and other synthe...

Urban areas are understood to be extraordinarily spatially heterogeneous. Spatial heterogeneity, and its causes, consequences, and changes, are central to ecological science. The social sciences and urban design and planning professions also include spatial heterogeneity as a key concern. However, urban ecology, as a pursuit that integrates across...

Large Amazonian rivers are characteristically subject to seasonal floods. We examine how inundation extent affects the partial pressure of carbon dioxide (pCO2) and CO2 outgassing in the Madeira River, a large tributary to the Amazon River. We show data from nine field campaigns performed between 2009 and 2011, complemented with data from one addit...

Research on urban ecosystems rapidly expanded in the 1990s and is now a central topic in ecosystem science. In this paper, we argue that there are two critical challenges for ecosystem science that are rooted in urban ecosystems: (1) predicting or explaining the assembly and function of novel communities and ecosystems under altered environmental c...

Nitrogen (N) pollution of freshwater, estuarine, and marine ecosystems is widespread and has numerous environmental and economic impacts. A portion of this excess N comes from urban watersheds comprised of natural and engineered ecosystems which can alter downstream N export. Studies of urban N cycling have focused on either specific ecosystems or...

The presence of pharmaceuticals, including illicit drugs in aquatic systems, is a topic of environmental significance because of their global occurrence and potential effects on aquatic ecosystems and human health, but few studies have examined the ecological effects of illicit drugs. We conducted a survey of several drug residues, including the po...

The effects of pharmaceuticals on aquatic ecosystems are the subject of increasing environmental concern. Of particular interest are a suite of drugs known as selective serotonin reuptake inhibitors (SSRIs), commonly prescribed to treat depression. SSRIs are now detected in the environment worldwide, but their effects on ecosystems are not well und...

Significance Acid rain has stripped forests of soil calcium, with consequences for forest health and downstream ecosystems. In 1999, researchers initiated a whole-watershed experiment, with the goal of replacing all the calcium lost. This experiment increased the pH and acid-neutralizing capacity of soils and streamwater, and forest growth increase...

The River Continuum Concept (RCC) predicts that food webs (and, in particular, invertebrates) of rivers in temperate, forested drainages should exhibit a longitudinal gradient from reliance on terrestrially derived organic matter (e.g., seasonally shed leaves) in the headwaters to autochthonous sources (e.g., algae) in the mid-orders, to suspended...

Ecosystem metabolism, that is, gross primary productivity (GPP) and ecosystem respiration (ER), controls organic carbon (OC) cycling in stream and river networks and is expected to vary predictably with network position. However, estimates of metabolism in small streams outnumber those from rivers such that there are limited empirical data comparin...

Nitrogen (N) pollution of freshwater, estuarine and marine ecosystems is widespread and has numerous environmental and economic impacts. A portion of this excess N comes from urban watersheds comprised of natural and engineered ecosystems that can alter downstream N export. Studies of urban N cycling have focused on either specific ecosystems or on...

The regulation and management of chemical contaminants rarely use community‐ and ecosystem‐level endpoints, partly due to a lack of suitable methods. To overcome this limitation, we propose contaminant exposure substrata ( CES ), an adaptation of the widely used nutrient‐diffusing substratum method, to assess responses of biofilm communities to che...

Aquatic macroinvertebrates are central to lentic and lotic food webs, and characterizing the items they consume is often useful for studies of trophic ecology and food webs. Macroinvertebrate gut contents have been examined frequently by aquatic ecologists, but to our knowledge, no protocol describing how to conduct quantitative gut-content analysi...

As natural resources become increasingly limited, the value of restoring contaminated sites, both terrestrial and aquatic, becomes increasingly apparent. Traditionally, goals for remediation have been set prior to any consideration of goals for ecological restoration. The goals for remediation have focused on removing or limiting contamination whil...

Nutrient transformation processes such as assimilation, dissimilatory transformation, and sorption to sediments are prevalent in benthic zones of headwater streams, but may also occur in the water column. The river continuum concept (RCC) predicts that water column processes become increasingly important with increasing stream size. We predicted th...

Mercury (Hg) and selenium (Se) biomagnify in aquatic food webs and are toxic to fish and wildlife. The authors measured Hg and Se in organic matter, invertebrates, and fishes in the Colorado River food web at sites spanning 387 river km downstream of Glen Canyon Dam (AZ, USA). Concentrations were relatively high among sites compared with other larg...

Dams and river regulation greatly alter the downstream environment for gross primary production (GPP) because of changes in water clarity, flow, and temperature regimes. We estimated reach-scale GPP in five locations of the regulated Colorado River in Grand Canyon using an open channel model of dissolved oxygen. Benthic GPP dominates in Grand Canyo...