Caryn C. Vaughn

• Doctor of Philosophy
• CEO at University of Oklahoma

Freshwater mussels and fish support many important ecosystem processes and functions in river systems that can be framed as ecosystem services. The ecosystem services provided by mussels and fish have been widely described; however, they are often not in the public forefront. Studies that link these invisible processes with perceived social benefit...

Ecosystem engineers alter habitat and resource availability within ecosystems, but the magnitude of these effects depends on abiotic context and spatial scale. We examined how the effects of freshwater mussels, an ecosystem engineer, changed with spatial scale. We combined a field enclosure experiment and comparative field study to evaluate associa...

The loose‐equilibrium concept (LEC) predicts that ecological assemblages change transiently but return towards an earlier or average structure. The LEC framework can help determine whether assemblages vary within expected ranges or are permanently altered following environmental change. Long‐lived, slow‐growing animals typically respond slowly to e...

Poyang Lake, China's largest freshwater lake, has high ecological and economic value. The area is a global hotspot of freshwater mussel diversity, and it supports an important dredge fishery for snails, which results in substantial mussel bycatch. The mussel fauna changed dramatically in the last two decades, and many large species disappeared from...

Animals are a critical component of biogeochemical cycles. While animal mediated fluxes of nutrients and energy have received considerable attention, the impacts of these fluxes on microbial community structure and function are comparatively understudied. Here, we investigated if freshwater mussel influences on biogeochemical cycling in stream sedi...

The impacts of animals on the biogeochemical cycles of major bioelements like C, N, and P are well-studied across ecosystem types. However, more than 20 elements are necessary for life. The feedbacks between animals and the biogeochemical cycles of the other bioelements are an emerging research priority. We explored how much freshwater mussels (Biv...

This document has been prepared in cooperation with Federal, Indigenous, and State malacologists (mollusk scientists), environmental toxicologists, restoration specialists, and other subject matter experts to provide best practices for freshwater mussel injury determination, early identification of restoration opportunities, injury quantification...

Emergent macrophytes can create important linkages between aquatic and terrestrial ecosystems. American water willow (Justicia americana) is an ecological engineer that provides structure and takes up nutrients in aquatic habitats but is subject to herbivory by terrestrial animals. Here, potential constraints that terrestrial herbivory, riparian sh...

Ecosystems provide essential services to people including food, water, climate regulation, and aesthetic experiences. Biodiversity can enhance and stabilize ecosystem function and the resulting services natural systems provide. Freshwater mollusks are a diverse group that provide a variety of ecosystem services through their feeding habits (e.g., f...

We identified 14 emerging and poorly understood threats and opportunities for addressing the global conservation of freshwater mussels over the next decade. A panel of 17 researchers and stakeholders from six continents submitted a total of 56 topics that were ranked and prioritized using a consensus-building Delphi technique. Our 14 priority topic...

Lakes and reservoirs are frequently monitored by researchers for elevated mercury concentrations in sportfish. Rivers and streams, especially those of smaller orders, are less frequently monitored for mercury contamination and nonsport fishes and invertebrates, although important components of the food web, are rarely examined. We addressed this ga...

Trophic interactions between mobile animals and their food sources often vector resource flows across ecosystem boundaries. However, the quality and quantity of such ecological subsidies may be altered by indirect interactions between seemingly unconnected taxa. We studied whether emergent macrophytes growing at the aquatic–terrestrial interface fa...

Freshwater mussels (Bivalvia: Unionoida) are globally imperilled and are the subjects of wide‐ranging conservation initiatives. This study combined traditional species‐monitoring surveys with a novel functional trait classification scheme and publicly available environmental data to assess potential environmental drivers of declining mussel abundan...

As body size often predicts energetic requirements and fecundity, understanding the drivers behind size variation is important. Neo‐Bergmann's rule states that larger individuals are found at higher latitudes and this size variation is attributable to temperature gradients. In ectotherms, this macroecological pattern has mixed support within the li...

Microbiomes are increasingly recognized as widespread regulators of function from individual organism to ecosystem scales. However, the manner in which animals influence the structure and function of environmental microbiomes has received considerably less attention. Using a comparative field study, we investigated the relationship between freshwat...

• In streams, unionoid mussels and fish form aggregations that exert bottom-up and top-down effects on food webs, but the magnitude and spatial extent of their effects are controlled by species traits. Sedentary mussels live burrowed in the sediment in patchily distributed dense aggregations (mussel beds) where they filter seston and provide a loca...

• Riverine species are governed by the physical (i.e. hydrodynamic) forces generated by flowing water. Freshwater species are also disproportionately imperilled compared to terrestrial and marine species in large part due to widespread anthropogenic alteration of the natural flow regimes to which organisms are adapted. Sedentary species such as fre...

Perspectives of white males have overwhelmingly dominated fisheries science and management in the USA. This dynamic is exemplified by bias against “rough fish”—a pejorative ascribing low‐to‐zero value for countless native fishes. One product of this bias is that biologists have ironically worked against conservation of diverse fishes for over a cen...

Lakes and reservoirs are frequently monitored by researchers for elevated mercury concentrations in sportfish. Rivers and streams, especially those of smaller orders, are less frequently monitored for mercury contamination. Mercury contamination in the environment comes predominantly from anthropogenic sources like artisanal gold mining and the bur...

Myriad anthropogenic factors have led to substantial declines in North America's freshwater mussel populations over the last century. A greater understanding of mussel dispersal abilities, genetic structure, and effective population sizes is imperative to improve conservation strategies. This study used microsatellites to investigate genetic struct...

The study of the relationships between freshwater organisms, pollution and public awareness has been little researched. The public’s perception of risk from pollution is a fundamental component in determining consumer behavior and promoting healthy habits. For instance, understanding how consumers perceive the risks associated with pollution can he...

The roles mobile animals and abiotic processes play as vectors for resource transfers between ecosystems (“subsidies”) are well studied, but the idea that resources from animals with limited mobility may be transported across boundaries through intermediate taxa remains unexplored. Aquatic plants (“macrophytes”) are globally distributed and may med...

Freshwater mussels are dominant ecosystem engineers in many streams throughout North America, yet they remain among the world's most imperiled fauna. Extensive research has quantified the ecological role of mussels in aquatic habitats, but little is known about the interaction between mussels and their surrounding physical and hydrodynamic habitat....

Animals exert both direct and indirect controls over elemental cycles, linking primary producer‐based (green) and decomposer‐based (brown) food webs through top‐down trophic interactions and bottom‐up element regeneration. Where animals are aggregated at high biomass, they create hotspots of elemental cycling. The relative importance of animal cont...

Between global climate change and anthropogenic water needs, freshwater systems are becoming more intermittent, stressing organisms adapted to perennial waters. Drought‐induced intermittency concentrates aquatic organisms into drying pools. These pools represent refugia from desiccation but apply other stressors, such as extreme temperatures and in...

Aggregations of freshwater mussels create patches that can benefit other organisms through direct habitat alterations or indirect stimulation of trophic resources via nutrient excretion and biodeposition. Spent shells and the shells of living mussels add complexity to benthic environments by providing shelter from predators and increasing habitat h...

Punctuated, mass mortality events are increasing for many animal taxa and are often related to climatic extremes such as drought. Freshwater mussels are experiencing increased mass mortality events linked to hydrologic drought. Because mussels play important functional roles in rivers it is important to understand the ecosystem effects of these die...

Freshwater mussels are declining globally, and effective conservation requires prioritizing research and actions to identify and mitigate threats impacting mussel species. Conservation priorities vary widely, ranging from preventing imminent extinction to maintaining abundant populations. Here, we develop a portfolio of priority research topics for...

Animals can play important roles in cycling nutrients [hereafter consumer-driven nutrient dynamics (CND)], but researchers typically simplify animal communities inhabiting dynamic environments into single groups that are tested under relatively static conditions. We propose a conceptual framework and present empirical evidence for CND that consider...

Bivalve molluscs are abundant in marine and freshwater ecosystems and perform important ecological functions. Bivalves have epifaunal or infaunal lifestyles but are largely filter feeders that couple the water column and benthos. Bivalve ecology is a large field of study, but few comparisons among aquatic ecosystems or lifestyles have been conducte...

The cover image is based on the Original Article Long‐term persistence of freshwater mussel beds in labile river channels, by Brandon J. Sansom et al., DOI: 10.1111/fwb.13175. Photo credit: Jamie March and Brandon Sansom.

Freshwater mussels play important roles in ecosystems and are globally imperiled. Adult mussels are sedentary and dispersal is as larvae attached to fish hosts and as juveniles in stream drift. Understanding juvenile dispersal is important for understanding the patchy distribution of adult mussels and for conservation. We propose the location in wh...

1. Freshwater mussels are among the world’s most imperilled species, and much effort has been expended to understand their precipitous decline. The current paradigm is that relative river bed stability over decades is critical to maintaining mussel beds at a given river reach. Such information, however, is in stark contrast to the fundamental under...

Freshwater mussels occur as large multi-species aggregations that are spatially heterogeneous in streams. Mussels provide trophic subsidies via nutrient excretion and biodeposition and their shells provide biogenic habitat. These factors often result in increased primary production and macroinvertebrate abundance in areas with high mussel biomass,...

Globally, environmental and social change in water-scarce regions challenge the sustainability of social-ecological systems. WaterSES, a sponsored working group within the Program for Ecosystem Change and Society, explores and compares the social-ecological dynamics related to water scarcity across placed-based international research sites with con...

Freshwater mussels occur as large multi-species aggregations that are spatially heterogeneous in streams. Mussels provide trophic subsidies via nutrient excretion and bio-deposition and their shells provide biogenic habitat. These factors often result in increased primary production and macroinvertebrate densities in areas with high mussel biomass,...

Differences in animal distributions and metabolic demands can influence energy and nutrient flow in an ecosystem. Through taxa-specific nutrient consumption, storage, and remineralization, animals may influence energy and nutrient pathways in an ecosystem. Here we show these taxa-specific traits can drive biogeochemical cycles of nutrients and alte...

Ecosystem services are the benefits that humans derive from ecosystems. Freshwater mussels perform many important functions in aquatic ecosystems, which can in turn be framed as the ecosystem services that they contribute to or provide. These include supporting services such as nutrient recycling and storage, structural habitat, substrate and food...

Fishes and mussels are prominent organisms in streams of eastern North America. Fish communities have large effects on mussel communities because mussels disperse as ectoparasitic larvae on fish hosts. Mussel communities influence the abundance and composition of algae and macroinvertebrates in streams by providing shell habitat and nutrient subsid...

The shifting baseline syndrome concept advocates for the use of historical knowledge to inform conservation baselines, but does not address the feasibility of restoring sites to those baselines. In many regions, conservation feasibility varies among sites due to differences in resource availability, statutory power, and land‐owner participation. We...

The PECS-WaterSES compares the social-ecological dynamics causing and caused by water scarcity and governance across international research sites with conflicting local and regional water needs and governance, including arid southern Spain, the south-central Great Plains of Oklahoma (US), and the Portneuf and Treasure Valleys, Idaho (US). WaterSES...

Mussels and fish are known to generate nutrient hotspots, but whether aggregations of these two disparate consumer groups overlap and interact to influence nutrient dynamics remains unexplored. Mussel beds created stable, long-term hotspots that may attract fishes by providing resource subsidies. Hence, we asked whether fish biomass accumulates dis...

Freshwater mussels are a unique guild of benthic invertebrates that are of ecological and conservation importance. Age and growth determination are essential to better understand the ecological role of mussels, and to effectively manage mussel populations. In this study, we applied dendrochronology techniques and Ford-Walford analyses to determine...

[This corrects the article DOI: 10.1002/ece3.1442.].

In 1998, a strategy document outlining the most pressing issues facing the conservation of freshwater mussels was published (NNMCC 1998). Beginning in 2011, the Freshwater Mollusk Conservation Society began updating that strategy, including broadening the scope to include freshwater snails. Although both strategy documents contained 10 issues that...

We performed a sociocultural preference assessment for a suite of ecosystem services provided by the Kiamichi River watershed in the south-central U.S., a region with intense water conflict. The goal was to examine how a social assessment of services could be used to weigh trade-offs among water resource uses for future watershed management and pla...

Organisms that live in flowing water need to compensate for downstream displacement. Mobile animals can compensate for displacement by actively swimming or crawling upstream, while sedentary animals need other means to retain their position. Freshwater mussels (Bivalvia, Unionidae) have limited movement as adults, and juveniles drift downstream aft...

North American freshwater mussels (Unionidae) are a diverse and imperilled fauna that are very sensitive to flow alterations. Previous attempts to develop environmental flows for mussels have struggled to accommodate their varied habitat requirements and complex life histories. We review what is known about the habitat requirements of mussels, how...

Extreme hydro-meteorological events such as droughts are becoming more frequent, intense, and persistent. This is particularly true in the south central USA, where rapidly growing urban areas are running out of water and human-engineered water storage and management are leading to broad-scale changes in flow regimes. The Kiamichi River in southeast...

In streams, the creation of nutrient‐transformation hotspots by aggregated organisms may have heterogeneous and strong cumulative influences on stream nutrient dynamics. Here, we examine the potential for aggregations of freshwater mussels to create such hotspots. We measured nitrogen ( N ) and phosphorus ( P ) excretion rates of six mussel species...

The flux of consumer-derived nutrients is recognized as an important ecosystem process, yet few studies have quantified the impact of these fluxes on freshwater ecosystems. The high abundance of bivalves in both marine and freshwater suggests that bivalves can exert large effects on aquatic food webs. The objective of our study was to determine the...

Nitrogen (N) fertilizer runoff into rivers is linked to nutrient enrichment, hydrologic alteration, habitat degradation and loss, and declines in biotic integrity in streams. Nitrogen runoff from agriculture is expected to increase with population growth, so tracking these sources is vital to enhancing biomonitoring and management actions. Unionid...

Ecosystem services are benefits humans derive from natural systems. These include direct services such as water, food and timber, regulating services like water purification and carbon storage, and cultural services such as recreation and spiritual enrichment. Freshwater mussels are a guild of sedentary, burrowing, long-lived, filter-feeding bivalv...

The flux of consumer-derived nutrients has been increasingly recognized as an important ecosystem process, yet few have quantified the impact of these fluxes on food webs. The objective of our study was to determine the importance of unionid mussel-derived nitrogen (MDN) relative to ecosystem demand and the food web. We fed mussels (Lampsilis siliq...

As large, long-lived filter feeders with high clearance rates, unionid mussels are capable of altering nutrient cycling in freshwater food webs. Because the effects of mussel communities on ecosystem processes result largely from their feeding behavior, we need to understand how they sample and process particulate matter. Our objective was to deter...

Droughts often pose situations where stream water levels are lowest while human demand for water is highest. Here we present results of an observational study documenting changes in freshwater mussel communities in two southern US rivers during a multi-year drought. During a 13-year period water releases into the Kiamichi River from an impoundment...

Nutrient cycling is a key process linking organisms in ecosystems. This is especially apparent in stream environments in which nutrients are taken up readily and cycled through the system in a downstream trajectory. Ecological stoichiometry predicts that biogeochemical cycles of different elements are interdependent because the organisms that drive...

1. Species richness and assemblage patterns of organisms are dictated by numerous factors, probably operating at multiple scales. Freshwater mussels (Unionidae) are an endangered, speciose faunal group, making them an interesting model system to study the influence of landscape features on organisms. In addition, landscape features that influence s...

Although biodiversity can increase ecosystem productivity and adjacent ecosystems are often linked by resource flows between them, the relationship between biodiversity and resource subsidies is not well understood. Here we test the influence of biodiversity on resource subsidy flux by manipulating freshwater mussel species richness and documenting...

Background/Question/Methods Freshwater mussels are large, long-lived suspension feeders that provide important ecosystem services in rivers such as biofiltration, nutrient recycling and nutrient storage. Mussels occur in speciose aggregations (mussel beds) at high biomass, and there are differences in biofiltration and nutrient excretion rates ac...

1. A critical need in conservation biology is to determine which species are most vulnerable to extinction. Freshwater mussels (Bivalvia: Unionacea) are one of the most imperilled faunal groups globally. Freshwater mussel larvae are ectoparasites on fish and depend on the movement of their hosts to maintain connectivity among local populations in a...

We examined the effect of species identity on ecosystem function across an environmental gradient by manipulating the relative dominance of three freshwater mussel species with divergent thermal preferences in mesocosms across a temperature gradient (15, 25, 35°C). We measured a suite of individual performance (oxygen consumption, nutrient excretio...

Changing environments can have divergent effects on biodiversity-ecosystem function relationships at alternating trophic levels. Freshwater mussels fertilize stream foodwebs through nutrient excretion, and mussel species-specific excretion rates depend on environmental conditions. We asked how differences in mussel diversity in varying environments...

Background/Question/Methods: Biodiversity increases ecosystem productivity and increased productivity in one ecosystem often subsidizes adjacent ecosystems, but little is known about how biodiversity affects resource subsidy flux between ecosystems. To this end, we conducted a laboratory mesocosm experiment and comparative field study to test the...

Background/Question/Methods Determining the ecological costs and benefits of in-stream flow regimes requires quantifying real, measurable ecological characteristics of rivers and determining how these change under various flow scenarios. Rivers in southeastern Oklahoma are known for their relatively pristine and abundant water and high biological...

Several decades of research have shown that biodiversity affects ecosystem processes associated with resource capture and the production of biomass within trophic levels. Although there are good reasons to expect that biodiversity influences non-trophic ecosystem processes, such as the physical creation or modification of habitat, studies investiga...

The large-scale impoundment of rivers has led to global declines in freshwater mussel populations. It is important to understand the mechanisms underlying these declines to initiate an effective recovery strategy. We examined population traits of three Quadrula species (Quadrula pustulosa, Q. cylindrica and Q. quadrula) at three locations that were...

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Human alterations to aquatic ecosystems are leading to decreases in species richness and biomass and subsequent changes in community composition. In many cases species losses are non-random: species with traits poorly adapted to the new environmental conditions suffer greater losses. We used long-term data from a southern US river, the Kiamichi Riv...

Six conclusions have emerged from recent research that complicate the ability to predict how biodiversity losses may affect ecosystem function: (1) species traits determine ecosystem function, (2) species within functional groups are not always ecological equivalents, (3) biodiversity losses include declines in the abundance of common species, (4)...

Freshwater mussels are one of the most threatened faunas in North America and worldwide, but little research has examined factors leading to successful reproduction (gamete development and fertilization success) in these species. We combined field and laboratory studies to determine the environmental factors influencing successful reproduction in t...

To increase the generality of biodiversity-ecosystem function theory, studies must be expanded to include real communities in a variety of systems. We modified J. W. Fox's approach to partition the influence of species richness on standing crop biomass (net biodiversity effect) of 21 freshwater mussel communities into trait-independent complementar...

We experimentally manipulated mussel community structure and observed mussel burrowing behavior in mesocosms held in a greenhouse. Vertical positions, vertical movements, and horizontal movements of Actinonaias ligamentina, Amblema plicata, Fusconaia flava, and Obliquaria reflexa were recorded during five 11-d trials. Community structure was manipu...

Freshwater mussels are found in dense, multi-species aggregations where the potential for resource partitioning should be high. One means by which mussels may be partitioning resources is through feeding on different food items. We compared gill morphology in four species of co-occurring freshwater mussels. We found differences in total gill surfac...

Revisamos el estado de conservación de las especies raras de mejillones y en peligro de extinción en 10 sitios de muestreo a largo plazo en el río Kiamichi y 5 sitios en el río Little en el sureste de Oklahoma. Encontramos poblaciones existentes de Arkansia wheeleri, Leptodea leptodon, Quadrula fragosa y Quadrula cylindrica cylindrica. Reportamos p...

The Poteau River, a major tributary of the Arkansas River, flows through the Ouachita Uplands of eastern Oklahoma and western Arkansas. The river has been harvested for mussels, historically by the Caddo Indians and recently for the pearl industry. We documented the current distribution and abundance of mussels in the river, compared this with hist...

The sustained decline in habitat quality and community integrity highlights the importance of understanding how communities and environmental variation interactively contribute to ecosystem services. We performed a laboratory experiment manipulating effects of acclimation temperature (5, 15, 25, and 35 degrees C) on resource acquisition, assimilati...

Freshwater mussel (Superfamily Unionoidea) communities are important components of food webs, and they link and influence multiple trophic levels. Mussels filter food from both the water column and sediment with ciliated gills. Differences in cilia structure and arrangement might allow mussel species to partition food resources. Mussels are omnivor...

We asked whether species richness or species identity contributed more to ecosystem function in a trait-based functional group, burrowing, filter-feeding bivalves (freshwater mussels: Unionidae), and whether their importance changed with environmental context and species composition. We conducted a manipulative experiment in a small river examining...

Over 70% of North American freshwater mussel species (families Unionidae and Margaritiferidae) are listed as threatened or endangered. Knowledge of the genetic structure of target species is essential for the development of effective conservation plans. Because Ambelma plicata is a common species, its population genetic structure is likely to be re...

An important goal in aquatic ecology is to determine the interacting variables that regulate community structure; however, complex biotic and abiotic interactions coupled with the significance of scale have confounded the interpretation of community data. We evaluated stream and riparian habitat features in southeastern Oklahoma, USA at a range of...

We surveyed the freshwater mussel fauna (Bivalvia: Unionidae) of the Mountain Fork River, a major tributary of the Little River in eastern Oklahoma and western Arkansas. We found 22 species of unionids as well as the exotic Asian clam (Corbicula fluminea). Total mussel abundance (mussels found/hour) ranged from 0 to 312 with a mean of 40 +/-84 indi...

In North America there is conflicting evidence concerning whether the invasive Asian clam, Corbicula fluminea, and native mussels (Unionidae), can successfully co-exist. One reason underlying disparate conclusions may be the different spatial scales at which data have been collected. We compared the distribution and abundance of native unionid muss...

Unionid mussels often occur as multispecies aggregates called mussel beds and in dense patches within the mussel beds themselves. Thus, their distributions are patchy at 2 spatial scales. We examined the association between mussel assemblage structure and macroinvertebrate assemblage structure at these 2 spatial scales in rivers of the Ouachita Hig...

1. We asked whether unionid mussels influence the distribution and abundance of co‐occurring benthic algae and invertebrates. In a yearlong field enclosure experiment in a south‐central U.S. river, we examined the effects of living mussels versus sham mussels (shells filled with sand) on periphyton and invertebrates in both the surrounding sediment...

1. Macroinvertebrate densities and community composition were examined at three spatial scales after substratum disturbance; among reaches along a longitudinal gradient, within reaches and within plots. Reaches consisted of sandstone outcrops that were separated by approximately 2 km of highly mobile sandy silt substratum. 2. Substrata were disturb...

1. A series of laboratory and field experiments was performed to determine if the preference of larvae of Helicopsyche borealis (Trichoptera: Helicopsychidae) for exposed rock surfaces in streams was related to patchiness of periphyton food. 2. At low current velocities in the laboratory larvae preferred food-saturated as opposed to food-depleted p...

Summarized here for the first time are all known records of amphipod crustaceans in Oklahoma. Data sources consisted of a thorough literature review as well as unpublished state, county, and site records by the authors and contributors to regional databases. Fourteen species in four families are currently recognized: Allocrangonyctidae (Allocran-go...

The Arkansas and the Red-two large, separate river basins-drain the southern Great Plains region of the US south of the Kansas River and north of the Texas-Gulf coastal drainages. Rivers of the region flow through the Southern Plains, Central Prairie, Ozark Highlands, Ouachita Highlands, and Mississippi Embayment "freshwater ecoregions." The rivers...