Browsing by Author "Entrekin, Sally A."

Now showing 1 - 11 of 11
  • Thumbnail Image
    Assessing Flow-driven Effects on Local and Downstream Water Quality in Central Appalachian Headwater Streams Influenced by Surface Coal Mining
    Schoenholtz, Stephen H.; McLaughlin, Daniel L.; Entrekin, Sally A.; Hotchkiss, Erin R.; Timpano, Anthony J.; Cianciolo, Thomas R.; Word, Clayton S. (Virginia Tech. Powell River Project, 2020-10)
  • Thumbnail Image
    Do biofilm communities respond to the chemical signatures of fracking? A test involving streams in North-central Arkansas
    Johnson, Wilson H.; Douglas, Marlis R.; Lewis, Jeffrey A.; Stuecker, Tara N.; Carbonero, Franck G.; Austin, Bradley, J.; Evans-White, Michelle A.; Entrekin, Sally A.; Douglas, Michael E. (BMC, 2017)
    Background: Unconventional natural gas (UNG) extraction (fracking) is ongoing in 29 North American shale basins (20 states), with ~6000 wells found within the Fayetteville shale (north-central Arkansas). If the chemical signature of fracking is detectable in streams, it can be employed to bookmark potential impacts. We evaluated benthic biofilm community composition as a proxy for stream chemistry so as to segregate anthropogenic signatures in eight Arkansas River catchments. In doing so, we tested the hypothesis that fracking characteristics in study streams are statistically distinguishable from those produced by agriculture or urbanization. Results: Four tributary catchments had UNG-wells significantly more dense and near to our sampling sites and were grouped as ‘potentially-impacted catchment zones’ (PICZ). Four others were characterized by significantly larger forested area with greater slope and elevation but reduced pasture, and were classified as ‘minimally-impacted’ (MICZ). Overall, 46 bacterial phyla/141 classes were identified, with 24 phyla (52%) and 54 classes (38%) across all samples. PICZ-sites were ecologically more variable than MICZ-sites, with significantly greater nutrient levels (total nitrogen, total phosphorous), and elevated Cyanobacteria as bioindicators that tracked these conditions. PICZ-sites also exhibited elevated conductance (a correlate of increased ion concentration) and depressed salt-intolerant Spartobacteria, suggesting the presence of brine as a fracking effect. Biofilm communities at PICZ-sites were significantly less variable than those at MICZ-sites. Conclusions: Study streams differed by Group according to morphology, land use, and water chemistry but not in biofilm community structure. Those at PICZ-sites covaried according to anthropogenic impact, and were qualitatively similar to communities found at sites disturbed by fracking. The hypothesis that fracking signatures in study streams are distinguishable from those produced by other anthropogenic effects was statistically rejected. Instead, alterations in biofilm community composition, as induced by fracking, may be less specific than initially predicted, and thus more easily confounded by agriculture and urbanization effects (among others). Study streams must be carefully categorized with regard to the magnitude and extent of anthropogenic impacts. They must also be segregated with statistical confidence (as herein) before fracking impacts are monitored.
  • Thumbnail Image
    Global patterns and drivers of ecosystem functioning in rivers and riparian zones
    Tiegs, Scott D.; Costello, David M.; Isken, Mark W.; Woodward, Guy; McIntyre, Peter B.; Gessner, Mark O.; Chauvet, Eric; Griffiths, Natalie A.; Flecker, Alex S.; Acuna, Vicenc; Albarino, Ricardo; Allen, Daniel C.; Alonso, Cecilia; Andino, Patricio; Arango, Clay; Aroviita, Jukka; Barbosa, Marcus V. M.; Barmuta, Leon A.; Baxter, Colden V.; Bell, Thomas D. C.; Bellinger, Brent; Boyero, Luz; Brown, Lee E.; Bruder, Andreas; Bruesewitz, Denise A.; Burdon, Francis J.; Callisto, Marcos; Canhoto, Cristina; Capps, Krista A.; Castillo, Maria M.; Clapcott, Joanne; Colas, Fanny; Colon-Gaud, Checo; Cornut, Julien; Crespo-Perez, Veronica; Cross, Wyatt F.; Culp, Joseph M.; Danger, Michael; Dangles, Olivier; de Eyto, Elvira; Derry, Alison M.; Diaz Villanueva, Veronica; Douglas, Michael M.; Elosegi, Arturo; Encalada, Andrea C.; Entrekin, Sally A.; Espinosa, Rodrigo; Ethaiya, Diana; Ferreira, Veronica; Ferriol, Carmen; Flanagan, Kyla M.; Fleituch, Tadeusz; Shah, Jennifer J. Follstad; Frainer, Andre; Friberg, Nikolai; Frost, Paul C.; Garcia, Erica A.; Lago, Liliana Garcia; Garcia Soto, Pavel Ernesto; Ghate, Sudeep; Giling, Darren P.; Gilmer, Alan; Goncalves, Jose Francisco, Jr.; Gonzales, Rosario Karina; Graca, Manuel A. S.; Grace, Mike; Grossart, Hans-Peter; Guerold, Francois; Gulis, Vlad; Hepp, Luiz U.; Higgins, Scott; Hishi, Takuo; Huddart, Joseph; Hudson, John; Imberger, Samantha; Iniguez-Armijos, Carlos; Iwata, Tomoya; Janetski, David J.; Jennings, Eleanor; Kirkwood, Andrea E.; Koning, Aaron A.; Kosten, Sarian; Kuehn, Kevin A.; Laudon, Hjalmar; Leavitt, Peter R.; Lemes da Silva, Aurea L.; Leroux, Shawn J.; Leroy, Carri J.; Lisi, Peter J.; MacKenzie, Richard; Marcarelli, Amy M.; Masese, Frank O.; Mckie, Brendan G.; Oliveira Medeiros, Adriana; Meissner, Kristian; Milisa, Marko; Mishra, Shailendra; Miyake, Yo; Moerke, Ashley; Mombrikotb, Shorok; Mooney, Rob; Moulton, Tim; Muotka, Timo; Negishi, Junjiro N.; Neres-Lima, Vinicius; Nieminen, Mika L.; Nimptsch, Jorge; Ondruch, Jakub; Paavola, Riku; Pardo, Isabel; Patrick, Christopher J.; Peeters, Edwin T. H. M.; Pozo, Jesus; Pringle, Catherine; Prussian, Aaron; Quenta, Estefania; Quesada, Antonio; Reid, Brian; Richardson, John S.; Rigosi, Anna; Rincon, Jose; Risnoveanu, Geta; Robinson, Christopher T.; Rodriguez-Gallego, Lorena; Royer, Todd V.; Rusak, James A.; Santamans, Anna C.; Selmeczy, Geza B.; Simiyu, Gelas; Skuja, Agnija; Smykla, Jerzy; Sridhar, Kandikere R.; Sponseller, Ryan; Stoler, Aaron; Swan, Christopher M.; Szlag, David; Teixeira-de Mello, Franco; Tonkin, Jonathan D.; Uusheimo, Sari; Veach, Allison M.; Vilbaste, Sirje; Vought, Lena B. M.; Wang, Chiao-Ping; Webster, Jackson R.; Wilson, Paul B.; Woelfl, Stefan; Xenopoulos, Marguerite A.; Yates, Adam G.; Yoshimura, Chihiro; Yule, Catherine M.; Zhang, Yixin X.; Zwart, Jacob A. (American Association for the Advancement of Science, 2019-01-09)
    River ecosystems receive and process vast quantities of terrestrial organic carbon, the fate of which depends strongly on microbial activity. Variation in and controls of processing rates, however, are poorly characterized at the global scale. In response, we used a peer-sourced research network and a highly standardized carbon processing assay to conduct a global-scale field experiment in greater than 1000 river and riparian sites. We found that Earth’s biomes have distinct carbon processing signatures. Slow processing is evident across latitudes, whereas rapid rates are restricted to lower latitudes. Both the mean rate and variability decline with latitude, suggesting temperature constraints toward the poles and greater roles for other environmental drivers (e.g., nutrient loading) toward the equator. These results and data set the stage for unprecedented “next-generation biomonitoring” by establishing baselines to help quantify environmental impacts to the functioning of ecosystems at a global scale.
  • Thumbnail Image
    Prioritizing Stream Restoration Projects in the City of Roanoke, VA: Tool Development & Case Study
    Thompson, Theresa M.; Hession, W. Cully; Huffman, Sidney; Entrekin, Sally A. (2022-06-06)
    The City of Roanoke (City) is currently evaluating potential stream restoration projects to achieve several watershed goals, including meeting total maximum daily load (TMDL) requirements, mitigating floods, recovering ecological function, and transforming the Roanoke River into a community asset (Figure 1). The overall project goal was to develop a prioritization process for stream restoration projects to help maximize benefits from restoration projects and to apply this process to one watershed as a case study. The stream assessment approach was developed based on indicator parameters for stream functions and biological stressors; assessment data were collected utilizing both desktop analyses and field surveys. The prioritization framework was then developed based on City goals, current literature, and best practices in stream restoration. The initial stream condition ranking was a quantitative assessment, scoring, and comparison of the stream conditions for each reach. The reaches were next screened based on the technical assessment of each function for each reach. This technical screening produced a short list of potential projects that were ranked according to technical and socioeconomic factors.
  • Thumbnail Image
    Prioritizing Stream Restoration Projects in the City of Roanoke: Peters Creek Case Study
    Thompson, Theresa M.; Hession, W. Cully; Huffman, Sidney; Entrekin, Sally A. (Virginia Tech Biological Systems Engineering Department, 2021-06-14)
    The City of Roanoke (City) is currently evaluating potential stream restoration projects to achieve several watershed goals, including meeting total maximum daily load (TMDL) requirements, mitigating floods, recovering ecological function, and transforming the Roanoke River into a community asset. The City retained Virginia Tech (VT) researchers to develop a stream reach prioritization methodology to help maximize watershed benefits for funds spent on stream restoration. The overall project goal was to develop a prioritization process for stream restoration projects and to apply this process to one watershed as a case study (Peters Creek). Using the results of this case study, the methodology will be further adapted to apply to all City watersheds...
  • Thumbnail Image
    Quantifying changes in macroinvertebrate community composition, biomass, and emergence in response to mining-induced salinization in central Appalachian streams
    James, Aryanna Lee (Virginia Tech, 2021-06-03)
    Many ecosystems are losing biodiversity, raising concern for the services they provide. However, the extent of loss is uncertain, especially for insects that use freshwater during their life. Further study is needed to assess freshwater insect abundances and diversity. In Central Appalachian streams, macroinvertebrate diversity declines in response to mining-induced salinization and resulting changes to ecosystem processes remain largely unknown, such as how the availability and movement of macroinvertebrate biomass is altered in stream food webs. However, taxa observed are dependent upon sampling effort that could bias diversity-process interpretation. Taxon sampling curves can be used to estimate sampling effort that maximizes the probability of complete community characterization. We sampled six streams in the Central Appalachian region for benthic macroinvertebrates and explored the number of samples needed to capture taxonomic richness in salinized streams. Sampling effort did not differ between reference and salinized streams, though more uneven distributions of macroinvertebrates in salinized streams seemed to necessitate greater sampling effort relative to reference streams. We also used taxon and trait-based sampling curves to expand our understanding of biodiversity and functional responses to environmental change. Because macroinvertebrate biomass and emergence can assess the movement and changes in organic material and energy in response to a salinization gradient, we added them as additional metrics. Macroinvertebrates may have varied responses to a stressor dependent upon life stage, suggesting that assessments relying only on immatures may not fully characterize the effects of salinization. We sampled benthic macroinvertebrate biomass and emergent insect biomass from six streams in the Central Appalachian region to be representative of a salinization gradient. We predicted benthic biomass would either decrease, be maintained by greater density and biomass of salt-tolerant taxa, or increase from a salt subsidy effect, while emergent biomass would decrease disproportionately relative to benthic biomass due to late instar and pupae succumbing to stress. Our results suggest that total benthic macroinvertebrate biomass is maintained along a salinization gradient despite the loss of salt-sensitive mayflies due to compensation by salt-tolerant taxa that experience a subsidizing effect. Emergent biomass was variable among streams with peak emergence occurring in spring, with no apparent negative response to increasing conductivity. The present study can help to further develop metrics of stream ecosystem processes in response to a disturbance gradient.
  • Thumbnail Image
    Quantifying macroinvertebrate structural and functional response to stream acidification and subsequent recovery in Shenandoah National Park
    McIntyre, Kelly Christine (Virginia Tech, 2021-07-14)
    Acid rain alters freshwater pH and ion composition, preventing organisms from performing essential bodily functions causing mortality. Macroinvertebrate communities in acidified streams are characterized by species loss in response to physiological stress and altered food quality resulting from the degradation of microbial (e.g., fungi on leaves) communities. Although freshwater acidification in the U.S. is lessening following reduced industrial emissions, little is known about macroinvertebrate recovery. Often, biotic recovery is assessed by looking at changes to what taxa and how many individuals are present in the community (e.g., richness, density). While providing a metric for change, changes in "who" is there (i.e., richness) doesn't necessarily tell us changes in "what" they are doing (i.e., function). The relationship between diversity and function requires linking a "who" to their "what" with direct measurements or as indicated by their traits. Traits are attributes of an organism that aggregate biological, morphological, and behavioral information and may relate to their success in a particular environment. For example, taxa that cannot survive with stream drying (not desiccation resistant) may only be found in streams with permanent water. Trait-based taxonomic metrics could bridge "who" and "what" and expand the impact of stream recovery assessments. My objective was to assess trends over time in water chemistry and macroinvertebrate taxonomic and trait richness and density following reduced industrial emissions. To do so, I studied two long-term data sets from Shenandoah National Park to assess trends in water chemistry and macroinvertebrate taxa and trait composition over a 30-year period to identify taxa and traits that are sensitive to acidification. I also measured how much biomass macroinvertebrates produced in a year (i.e., secondary production) in two streams (1 acidified; 1 not acidified) to determine taxa and traits that are functionally sensitive to acidification. I used these structural and functional measures of sensitivity to determine if changes in trait richness or density predict changes in the function of that trait (e.g., secondary production). Changes over time show that streams have some recovery from acid rain with increasing stream pH and a greater number of taxa and traits present in the community. Changes in taxa were greater than changes in traits over time. While this result was expected as multiple taxa make up each trait category, it may also suggest minimal or delayed functional recovery over time. Still, macroinvertebrate secondary production indicated that function did differ with differences in acidification. Therefore, observed small changes in traits over time mirror prior studies that found other variables, such as competition for food or space, delay or inhibit macroinvertebrates from returning to the recovering streams. Additionally, there were similarities between traits changing over time and the secondary production of traits that differed between more and less acidified streams. Taxa characterized by long life spans and large body size (e.g., semivoltine, long adult life, slow seasonal development) appeared to be the most sensitive to changes in acidification. These findings suggest that some compositional attributes, like taxonomic or trait richness, may predict functional changes measured as secondary production while others, such as density, do not.
  • Thumbnail Image
    Quantitative Food Webs Indicate Modest Increases in the Transfer of Allochthonous and Autochthonous C to Macroinvertebrates Following a Large Wood Addition to a Temperate Headwater Stream
    Entrekin, Sally A.; Rosi, Emma J.; Tank, Jennifer L.; Hoellein, Timothy J.; Lamberti, Gary A. (2020-05-06)
    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 secondary invertebrate production via modified habitat and resources. Wood additions are commonly used as stream restoration tools for habitat improvements that can restore or strengthen food web connections; however, changes in carbon (C) flow through food webs are rarely measured because of time and expense. We quantified allochthonous and autochthonous C flow through aquatic macroinvertebrate communities 1 year before and 2 years after an experimental addition of large wood, compared to macroinvertebrates in an upstream control, in a temperate headwater stream. We predicted wood additions increase macroinvertebrate consumption and assimilation of allochthonous and autochthonous C through retention of leaves and altered flow-paths that expose more gravel and cobble for periphyton colonization. Macroinvertebrate allochthonous C assimilation tended to increase in years with greater organic matter retention and autochthonous C increased with more exposed gravel and cobble across seasons and between reaches. While the effect of wood addition on C flow through the macroinvertebrate community was minimal, it increased by similar to 20% relative to the control from an increase in production and C assimilation of common mayfly and caddisfly scrapers, Baetis and Glossossoma. Because the amount of organic matter retained and coarse substrate exposed corresponded with C form and amount consumed, restoration of large wood has the potential to increase organic matter C trophic transfer.
  • Thumbnail Image
    Stream Vulnerability to Widespread and Emergent Stressors: A Focus on Unconventional Oil and Gas
    Entrekin, Sally A.; Maloney, Kelly O.; Kapo, Katherine E.; Walters, Annika W.; Evans-White, Michelle A.; Klemow, Kenneth M. (PLOS, 2015-09-23)
    Multiple stressors threaten stream physical and biological quality, including elevated nutrients and other contaminants, riparian and in-stream habitat degradation and altered natural flow regime. Unconventional oil and gas (UOG) development is one emerging stressor that spans the U.S. UOG development could alter stream sedimentation, riparian extent and composition, in-stream flow, and water quality. We developed indices to describe the watershed sensitivity and exposure to natural and anthropogenic disturbances and computed a vulnerability index from these two scores across stream catchments in six productive shale plays. We predicted that catchment vulnerability scores would vary across plays due to climatic, geologic and anthropogenic differences. Across-shale averages supported this prediction revealing differences in catchment sensitivity, exposure, and vulnerability scores that resulted from different natural and anthropogenic environmental conditions. For example, semi-arid Western shale play catchments (Mowry, Hilliard, and Bakken) tended to be more sensitive to stressors due to low annual average precipitation and extensive grassland. Catchments in the Barnett and Marcellus-Utica were naturally sensitive from more erosive soils and steeper catchment slopes, but these catchments also experienced areas with greater UOG densities and urbanization. Our analysis suggested Fayetteville and Barnett catchments were vulnerable due to existing anthropogenic exposure. However, all shale plays had catchments that spanned a wide vulnerability gradient. Our results identify vulnerable catchments that can help prioritize stream protection and monitoring efforts. Resource managers can also use these findings to guide local development activities to help reduce possible environmental effects.
  • Thumbnail Image
    A Study of Neonicotinoid Seed Treatments in Bt Maize: Insect Resistance Management, Efficacy, and Environmental Fate
    Bekelja, Kyle (Virginia Tech, 2022-06-10)
    Roughly 79-100% of maize in the United States (US) is treated with a neonicotinoid seed treatment (NST), and transgenic (GMO) maize, Zea mays L. (Poaceae), that produces insecticidal toxins by way of genes derived from Bacillus thuringiensis (Bt), occupies more than 75% of maize acreage. Among a variety of secondary pests targeted by NSTs, the primary soil-dwelling pest targeted by Bt maize is the western corn rootworm (WCR), Diabrotica virgifera virgifera LeConte (Coleoptera: Chrysomelidae). Transgenic Bt technology has dramatically reduced insecticide use for WCR, and insect resistance poses the greatest threat to its utility. To delay resistance to Bt traits, in 2010 the US Environmental Protection Agency (EPA) approved a "refuge-in-a-bag" (RIB) insect resistance management (IRM) strategy, where 5% of seeds do not express Bt toxins (i.e., "refuge" maize). The RIB strategy is intended to preserve Bt trait effectiveness if mating between 'resistant' insects from Bt plants and 'susceptible' insects from refuge plants occurs at a high enough frequency. Investigations into the effectiveness of RIB for WCR have shown that beetles emerged from Bt plants tend to vastly outnumber beetles emerged from refuge plants, which contributes to low rates of mixed mating. Large proportions of Bt beetles is one of several factors that contributes to resistance development, and resistance to all currently-available WCR-Bt traits has been documented. I conducted field experiments in two regions (Indiana and Virginia) comparing refuge beetle proportions in NST-treated (NST+) and NST-untreated (NST-) 5% RIB maize, to determine whether NSTs may be limiting refuge beetle emergence. To assess advantages of combining use of Bt and NSTs, I compared stand, root injury rating, and yield between NST+, NST-, Bt and non-Bt maize in both states. I also measured neonicotinoid residues in soil, water, and stream sediment within and surrounding fields of maize, to study the off-site movement and soil residence time of these compounds. I found that 5% seed blends did not produce large populations of refuge beetles in any site-year, and that NSTs showed inconsistent effects on refuge beetle populations. Treatment comparisons showed inconsistent benefits of NSTs when combined with Bt traits. I detected neonicotinoid residues in soil matrices throughout the growing season (range: 0 – 417.42 ppb), including prior to planting, suggesting year-round presence of these compounds. My results suggest that, while the effects of NSTs on Bt IRM may be inconsistent, the benefits of universally applying NSTs to Bt maize for soil pests may not be worth the ecological costs of doing so in all cases.
  • Thumbnail Image
    Taxon and trait-based sampling curves can be used as a tool for assessing impairment in salinized headwater streams
    James, Aryanna; Pence, Rachel A.; Pond, Gregory; Schoenholtz, Stephen H.; Timpano, Anthony J.; Zipper, Carl E.; Entrekin, Sally A. (Elsevier, 2022-06-01)
    Many ecosystems are losing biodiversity, raising concern for the services they provide. However, the extent of loss is uncertain, especially for diverse insects, because of incomplete sampling. Modeling techniques for estimating upper bounds on diversity are needed to assess benthic freshwater insect abundances, taxa richness, and diversity because some species are declining at alarming rates while others are increasing. In central Appalachian streams of the U.S.A., aquatic insect communities have lost diversity following salinization caused by mining activities. However, the number of taxa observed are dependent upon sampling effort. Incomplete sampling could misrepresent biodiversity and functional losses. Our goal was to use taxon sampling curves to estimate sampling effort required to maximize the probability of accurate benthic macroinvertebrate characterization in dominant riffle habitats of headwater streams. We collected 5 to 10 quantitative benthic macroinvertebrate samples in each of six, first-order streams in the central Appalachian region. For our single-habitat, mesoscale approach, we predicted: (1) macroinvertebrate taxa richness would be the most robust indicator of salinization response compared to diversity, evenness, and density, (2) less sampling effort would be needed to capture taxonomic richness in salinized streams compared to reference streams, and (3) response diversity would also be lower in salinized streams because select trait states would be represented by fewer taxa. Results suggested nominally lower taxa richness, evenness, and diversity in some salinized streams but not in all despite greater or more variable within-stream densities. Nonetheless, sampling effort required to characterize macroinvertebrate communities did not differ between reference and salinized streams, though uneven within-stream taxa distributions corresponded with greater sampling effort requirements for complete characterization. Benthic macroinvertebrate community characteristics were different where higher densities and richness of small-bodied and fast-developing taxa were more common in salinized streams. Response diversity depended on trait states. For example, only about five shredder taxa were represented in salinized streams compared to eight taxa in reference streams. Despite some indication of lower response diversity across some functional feeding groups, more than five samples were needed for robust comparisons. Taxon and trait-based sampling curves suggest that greater overall sampling effort is needed and equal samples per stream was critical for complete diversity assessments regardless of the level of mining-induced salinization. Model-based sampling curves can serve as a tool to assess upper bounds on diversity metrics and sample-effort rigor.