Ryan M. Utz

Improving the culture of interdisciplinary collaboration in ecology by expanding measures of success

Interdisciplinary collaboration is essential to understand ecological systems at scales critical to human decision making. Current reward structures are problematic for scientists engaged in interdisciplinary research, particularly early career researchers, because academic culture tends to value only some research outputs, such as primary-authored publications. Here, we present a framework for the costs and benefits of collaboration, with a focus on early career stages, and show how the implementation of novel measures of success can help defray the costs of collaboration. Success measures at team and individual levels include research outputs other than publications, including educational outcomes, dataset creation, outreach products (eg blogs or social media), and the application of scientific results to policy or management activities. Promotion and adoption of new measures of success will require concerted effort by both collaborators and their institutions. Expanded measures should better reflect an...

Increased River Alkalinization in the Eastern U.S.

The interaction between human activities and watershed geology is accelerating long-term changes in the carbon cycle of rivers. We evaluated changes in bicarbonate alkalinity, a product of chemical weathering, and tested for long-term trends at 97 sites in the eastern United States draining over 260,000 km(2). We observed statistically significant increasing trends in alkalinity at 62 of the 97 sites, while remaining sites exhibited no significant decreasing trends. Over 50% of study sites also had statistically significant increasing trends in concentrations of calcium (another product of chemical weathering) where data were available. River alkalinization rates were significantly related to watershed carbonate lithology, acid deposition, and topography. These three variables explained ~40% of variation in river alkalinization rates. The strongest predictor of river alkalinization rates was carbonate lithology. The most rapid rates of river alkalinization occurred at sites with highest inputs of acid deposition and highest elevation. The rise of alkalinity in many rivers throughout the Eastern U.S. suggests human-accelerated chemical weathering, in addition to previously documented impacts of mining and land use. Increased river alkalinization has major environmental implications including impacts on water hardness and salinization of drinking water, alterations of air-water exchange of CO2, coastal ocean acidification, and the influence of bicarbonate availability on primary production.

Density-dependent individual growth and size dynamics of central Appalachian brook trout (Salvelinus fontinalis)

Density-dependent aggression, emigration, mortality, and individual growth have been identified in wild lotic salmonid populations. However, most work is limited to fish in the genus Salmo, and few studies consider density dependency coupled with observations of energy acquisition. We attempt to quantify density-dependent growth, size, and energy acquisition for a population of brook trout (Salvelinus fontinalis) in Appalachia, where the species is food-limited and population densities are low. Brook trout populations were intensely monitored over the course of 2 years at several sites within a watershed in eastern West Virginia. Tagging provided specific growth estimates, and diet analyses allowed for estimation of energy acquisition relative to maintenance requirements for adult fish. Young-of-the-year (YOY) brook trout exhibited density-dependent size relationships, but the intensity of density dependency varied substantially among months, with progressively decreasing slopes. Adult individual growth a...

Variation in physicochemical responses to urbanization in streams between two Mid-Atlantic physiographic regions

Urban development substantially alters the physicochemistry of streams, resulting in biodiversity and ecosystem function loss. However, interregional comparisons of physicochemical impact in urban streams suggest that geoclimatic heterogeneity may influence the extent of degradation. In the Mid-Atlantic United States, the adjacent Coastal Plain and Piedmont physiographic provinces possess distinctly different hydrogeomorphic properties that may influence how stream ecosystems respond to urbanization. Recent bioassessments have demonstrated that biotic sensitivity to urbanization is relatively acute in the Piedmont, suggesting that physicochemical change as a consequence of urbanization may be greater in that province. We compared hydrologic, chemical, and thermal characteristics of Mid-Atlantic Coastal Plain and Piedmont first- through fifth-order streams along gradients of impervious surface cover (ISC) at multiple spatial scales. Linear models were applied to test if conditions in rural streams and the degree of impact from ISC varied between provinces. Mean and maximum summer temperatures in Piedmont streams increased more per unit of ISC than in the Coastal Plain. Contrary to expectations, however, variables that quantified high-flow event frequency, magnitude and duration, exhibited significantly greater impact along the ISC gradient in the Coastal Plain. Most chemical changes associated with increasing ISC were similar in the two provinces, although the interregional chemical composition of rural streams differed substantially for most parameters. Our findings demonstrate consistent interregional heterogeneity in stream ecosystem responses to urbanization. Landscape-scale management decisions with stream ecosystem conservation, mitigation, or restoration as a goal must therefore carefully consider the geoclimatic context in order to maximize effectiveness.

Freshwater salinization syndrome on a continental scale

Significance Salinization and alkalinization impact water quality, but these processes have been studied separately, except in arid regions. Globally, salinization has been largely attributed to agriculture, resource extraction, and land clearing. Alkalinization has been attributed to recovery from acidification, with less recognition as an environmental issue. We show that salinization and alkalinization are linked, and trends in these processes impact most of the drainage area of the United States. Increases in salinity and alkalinity are caused by inputs of salts containing strong bases and carbonates that originate from anthropogenic sources and accelerated weathering. We develop a conceptual model unifying our understanding of salinization and alkalinization and its drivers and impacts on fresh water in North America over the past century. Salt pollution and human-accelerated weathering are shifting the chemical composition of major ions in fresh water and increasing salinization and alkalinization across North America. We propose a concept, the freshwater salinization syndrome, which links salinization and alkalinization processes. This syndrome manifests as concurrent trends in specific conductance, pH, alkalinity, and base cations. Although individual trends can vary in strength, changes in salinization and alkalinization have affected 37% and 90%, respectively, of the drainage area of the contiguous United States over the past century. Across 232 United States Geological Survey (USGS) monitoring sites, 66% of stream and river sites showed a statistical increase in pH, which often began decades before acid rain regulations. The syndrome is most prominent in the densely populated eastern and midwestern United States, where salinity and alkalinity have increased most rapidly. The syndrome is caused by salt pollution (e.g., road deicers, irrigation runoff, sewage, potash), accelerated weathering and soil cation exchange, mining and resource extraction, and the presence of easily weathered minerals used in agriculture (lime) and urbanization (concrete). Increasing salts with strong bases and carbonates elevate acid neutralizing capacity and pH, and increasing sodium from salt pollution eventually displaces base cations on soil exchange sites, which further increases pH and alkalinization. Symptoms of the syndrome can include: infrastructure corrosion, contaminant mobilization, and variations in coastal ocean acidification caused by increasingly alkaline river inputs. Unless regulated and managed, the freshwater salinization syndrome can have significant impacts on ecosystem services such as safe drinking water, contaminant retention, and biodiversity.

Ecological resistance in urban streams: the role of natural and legacy attributes

Urbanization substantially changes the physicochemical and biological characteristics of streams. The trajectory of negative effect is broadly similar around the world, but the nature and magnitude of ecological responses to urban growth differ among locations. Some heterogeneity in response arises from differences in the level of urban development and attributes of urban water management. However, the heterogeneity also may arise from variation in hydrologic, biological, and physicochemical templates that shaped stream ecosystems before urban development. We present a framework to develop hypotheses that predict how natural watershed and channel attributes in the pre-urban-development state may confer ecological resistance to urbanization. We present 6 testable hypotheses that explore the expression of such attributes under our framework: 1) greater water storage capacity mitigates hydrologic regime shifts, 2) coarse substrates and a balance between erosive forces and sediment supply buffer morphological changes, 3) naturally high ionic concentrations and pH pre-adapt biota to water-quality stress, 4) metapopulation connectivity results in retention of species richness, 5) high functional redundancy buffers trophic function from species loss, and 6) landuse history mutes or reverses the expected trajectory of eutrophication. Data from past comparative analyses support these hypotheses, but rigorous testing will require targeted investigations that account for confounding or interacting factors, such as diversity in urban infrastructure attributes. Improved understanding of the susceptibility or resistance of stream ecosystems could substantially strengthen conservation, management, and monitoring efforts in urban streams. We hope that these preliminary, conceptual hypotheses will encourage others to explore these ideas further and generate additional explanations for the heterogeneity observed in urban streams.

Urban stream renovation: incorporating societal objectives to achieve ecological improvements

Pervasive human impacts on urban streams make restoration to predisturbance conditions unlikely. The effectiveness of ecologically focused restoration approaches typically is limited in urban settings because of the use of a reference-condition approach, mismatches between the temporal and spatial scales of impacts and restoration activities, and lack of an integrative approach that incorporates ecological and societal objectives. Developers of new frameworks are recognizing the opportunities for and benefits from incorporating societal outcomes into urban stream restoration projects. Social, economic, cultural, or other benefits to local communities are often opportunistic or arise indirectly from actions intended to achieve ecological outcomes. We propose urban stream renovation as a flexible stream improvement framework in which short-term ecological and societal outcomes are leveraged to achieve long-term ecological objectives. The framework is designed to provide additional opportunities for beneficial outcomes that are often unattainable from ecologically focused restoration approaches. Urban stream renovation uses an iterative process whereby short-term ecological and societal outcomes generate public support for future actions, which may provide opportunities to address catchment-level causes of impairment that often exist across broad temporal scales. Adaptive management, education, and outreach are needed to maintain long-term public engagement. Thus, future work should focus on understanding how ecological and societal contexts interact, how to assess societal outcomes to maintain stewardship, developing new methods for effective education and outreach, and multidisciplinary collaborations. We discuss potential abuses and the importance of linking societal outcomes to long-term ecological objectives.

Interregional variation in urbanization-induced geomorphic change and macroinvertebrate habitat colonization in headwater streams

Abstract Urban land use alters channel morphometry, particle size structure, and sediment-transport dynamics in stream ecosystems, thereby degrading the habitat of aquatic organisms. However, stream form varies substantially among geoclimatic settings, and, thus, the degree of negative effects induced by urbanization may be region-specific. Biota in streams of the Coastal Plain ecoregion of the eastern US consistently show greater tolerance to urban land use than do biota of the adjacent Piedmont, potentially because of a disparity in geomorphic degradation between ecoregions. We quantified channel morphometry, particle mobility, sediment deposition, and floodwater chemistry in similarly sized rural and urban streams of both ecoregions to detect differences in urbanization-induced geomorphic change. Macroinvertebrate rates of recolonization in patches of disturbed benthic habitat also were monitored. No differences in channel morphometry were observed among treatment groups. Riffle particle sizes were significantly larger in urban than in rural Piedmont streams, but a corresponding disparity was absent in Coastal Plain streams. Particle mobility increased in urban settings uniformly between ecoregions. However, transported particles were substantially larger in Piedmont streams. Sediment deposition was higher overall in Coastal Plain streams but more affected by urbanization in Piedmont streams. Macroinvertebrate density in the disturbed habitat rose faster over time in Coastal Plain than in Piedmont streams. Results suggest that geomorphic degradation is greater in Piedmont streams and that organisms may be adapted to benthic instability in Coastal Plain streams. In addition, our findings demonstrate that ecosystem-scale responses of streams to urbanization may vary inherently among geoclimatic settings.

Disproportionate Relative Importance of a Terrestrial Beetle Family (Coleoptera: Scarabaeidae) as a Prey Source for Central Appalachian Brook Trout

Abstract Brook trout Salvelinus fontinalis and other salmonids in Appalachia typically inhabit headwater watersheds, where food resources may limit growth. We monitored the feeding trends of a brook trout population in central Appalachia over the course of 2 years to determine variation in feeding intensity and important prey items. One terrestrial beetle family, Scarabaeidae, provided a disproportionate amount of energy during the only time of year when brook trout were feeding substantially above maintenance ration. Scarab beetles contributed 39.6% of all energy consumed during May and June of both years, though the number of fish with one or more scarabaeids present in the stomach varied by month (22.2–51.7%). The species composition of scarab beetles consumed suggested that four species are of particular importance. Our findings imply that scarabaeids represent a considerably important prey taxon for brook trout in the region. Considering the foraging habits of the scarabaeid species in question, the ...

Ecological Thresholds and Resilience in Streams

Ecological thresholds and resilience are powerful heuristics for understanding how lotic ecosystems change. Ecosystems may exist in self-organized states based on their taxonomic composition or the range of ecosystem functions, which are influenced by environmental drivers such as thermal or hydrologic regimes, channel morphology, and availability of nutrients. Changes in these underlying drivers may exceed an ecosystem’s ability to maintain its characteristic attributes and shift the system into alternative states of organization, which are often regarded as degraded or undesired. The boundaries where transitions occur are known as ecological thresholds and often show a rapid ecosystem response across a relatively small change in the environmental driver. Resilient ecosystems have the capacity to retain attributes in the face of disturbances. However, at some disturbance magnitude an ecosystem may become altered, and the magnitude necessary for a regime shift decreases as resilience declines. While ecological resilience remains largely metaphorical in lotic ecosystems, we describe some approaches for identification and assessment.