Full Program


Click on the title of a talk to view the abstract. 


8:30am-9:00am // Clark Hall // Mural Room

Opening Remarks.

8:50am-9:00am // Clark Hall // Mural Room


9:00-10:15am // Clark Hall // Room 133

9:00-9:15 am Ecosystem function and supporting ecosystem services of three land-use types under variable management in northwestern Virginia. Kelsey Huelsman and Howard Epstein
The Ecosystem Services (ES) concept, despite its interdisciplinary approach and ever-growing influence in policy decision-making, still has shortcomings: supporting services, the foundation for all other ES, are often ignored, and when they are discussed, resource inputs required by managed systems in order to produce ES are not widely considered, nor are detrimental impacts of functions (disservices). Biogeochemical properties, processes, and functions were measured in three land-use types under variable human management: agriculture, native prairie, and non-native early successional field. The resultant supporting ES were adjusted based on disservices and the ecological cost of human management, using a novel “net services” approach. Aboveground production was highest in the agricultural field and lowest in the prairie. Net N mineralization (NNM) and vertical N flux within the soil profile (indicative of leaching) was highest in the agricultural field, intermediate in the early successional field, and lowest in the native prairie. The service of NNM, positively correlated with vertical N flux in the soil profile, must be reduced to account for the disservice of leaching: most in the agricultural field, followed by the early successional field, and least in the prairie. The ecological cost of management in the agricultural field is greatest, so its benefits must be further reduced. By utilizing this approach, the early successional field provides the greatest level of “net services” relative to other land-use types, followed by the native prairie, then agriculture. This research is vital to further the ES discussion and to improve land-use decision-making practices.

Author affiliations: UVA Department of Environmental Sciences

9:15-9:30 am ALAN Effects on Decomposition. Melissa Hey, Howard Epstein1, Kyle Haynes1,2
There is mounting evidence that artificial light at night (ALAN) has unintended consequences for ecological communities. However, few have explored the ecosystem impacts of this sensory pollutant. Here we present findings from two field experiments in which we explored how ALAN affects (1) the rate of litter breakdown among increasingly complex invertebrate communities and (2) the community composition and macro-arthropod abundance in a complex system. In our first study, we found a higher proportion of decomposition in ALAN treated plots. This was most evident in our highest community complexity structure, leading us to carry out our second experiment the following year. In that study (2), we hoped to illuminate some of the mechanisms for greater decomposition under ALAN by investigating the arthropod abundance and trophic composition.

Author affiliations: 1UVA Department of Environmental Sciences, 2Blandy Experimental Farm

9:30-9:45 am An analysis of introduced and native mason bee diversity and distribution across the Commonwealth of Virginia using trap-nesting techniques. Kathryn LeCroy, Rachel Bigelow, Cole Carrano, Samuel Grimmelbein, Dat Ha, Noah Jacobs, John Leahy, Nayoung Lee, Magnolia Matthews, John McCormack, Swathi Mukkamala, Sara Richardson, Sophia Rosenberg, Sebastien Simko, Hans Theiler, Jing Wang, T'ai Roulston
The effects of stressors such as habitat loss, pesticide use, introduced species, and disease dynamics on bee populations are becoming increasingly well-documented, especially for the European honeybee (Apis mellifera) and bumblebees (genus Bombus). However, we still have not evaluated impacts of these stressors on wild populations of bee species that provide critical pollination services, in part because the general understanding of their distribution and diversity remains unclear, including mason bees (genus Osmia). With the help of 100 citizen scientists, we deployed 1,800 mason bee nests across the Commonwealth of Virginia and screened nests for native and introduced species presence, abundance, and evidence of mortality. We analyzed these factors across different nest hole sizes, nesting substrates, and landscape types. Preliminary results indicate significant differences in mason bee occupancy across landscape types and nesting substrates. Future work includes evaluating nest associate incidence and analyzing patterns of interspecies succession within nests.

Author affiliations: UVA Department of Environmental Sciences

9:45-10:00 am UVA’s Institutional Nitrogen Footprint: Meeting the 25% Reduction Goal by 2025. Rachel McGill, Alicia Zheng, Elizabeth Dukes, Andrew Pettit, James Galloway
The goal of this project is to track the university’s nitrogen (N) footprint over time to determine reductions needed to reach the university-wide reduction goal of a 25% by 2025, from the 2010 baseline. The 2014 and 2016 nitrogen footprints were calculated and analyzed for reduction progress, with 11% and 17% reductions respectively from the baseline. However, Business As Usual (BAU) projections show that reductions will only be 2% in 2025 due to growth in UVA population and square footage. This requires projection and scenario analysis to identify initiatives that can be implemented to reduce nitrogen emissions and reach the reduction goal. Our project has worked with stakeholders from the Office for Sustainability, Facilities Management, UVA Dining, Darden School of Business, and UVA Health System Dining to identify and analyze scenario opportunities relating to food, energy, and wastewater to reach 25% reductions by 2025. By researching these opportunities, documenting them in a Nitrogen Action Plan, and continued collaboration with stakeholders, our team aims to determine feasible strategies to ensure the nitrogen goal is met.

Author affiliations: UVA Department of Environmental Sciences

10:00-10:15 am Cut the engine: potential gains from a no idling policy at UVA. Jake Smith, Melissa Martinez, Maame Esi-Eghan, Abby Heher, Maya Korb, Zoe Morse, Jasmyn Noel, Danny Rivera, Stefan Woodson, and Prof. Deborah Lawrence
During the spring semester of 2018, the UVA Transloc service was used to record the idling times of UTS buses during their normal routes. Our goal was to determine the impact of transit bus idling at UVA on 1) greenhouse gas emissions, 2) air pollution and 3) fuel costs. According to the EPA, diesel engines are a large contributor of pollutants such as VOCs and nitric oxides, as well as carbon (CO and CO2). The idling of engines also contributes to financial waste, with a standard bus using 0.97 gallons of fuel per idle hour. Therefore, limiting how long buses idle their engines during their route is environmentally and economically ideal. Our observations indicate that UTS buses idle on average 25% of their total time on route. The estimated CO2 emissions from idling over the course of a year (at the rates observed in this study) is 70 metric tons, or 3.3% of UTS CO2 emissions estimated by fuel use for 2016-2017. Over the entire bus system, idling produces 2.1 g of PM2.5, 5.3 g of VOCs, and 120 g of nitric oxides every hour. The estimated annual fuel cost of idling is $20,705. Further data analysis is needed to determine 1) how idling times depend on number of buses on route and time of day, and 2) how pollutants affect the local air environments at key idling points like the UVA Chapel and Alderman Library.

Author affiliations: UVA Department of Environmental Sciences


(15 min)


10:30-11:45am // Clark Hall // Room 133

10:30-10:45 am Lake Ice and Climate. Daniel Schmidt, Kevin Grise, and Mike Pace
Many lakes and rivers at high northern latitudes freeze every winter, and this freezing and the subsequent spring ice break-up can be a key factor for determining ecological dynamics. Records of spring ice break-up dates in the Northern Hemisphere have been maintained for decades, or in some cases, centuries. In these records, we can detect a trend toward earlier ice-off dates, as would be expected from long-term climate change. However, we can also identify modes of natural climate variability that significantly impact the short-term behavior of ice-off time series. In particular, the North Atlantic Oscillation (NAO), Pacific-North American Pattern (PNA), and to a lesser degree the El Niño-Southern Oscillation (ENSO) explain a substantial fraction of the interannual variance in melt dates, while lower-frequency oscillations such as the Pacific Decadal Oscillation (PDO) and Atlantic Multidecadal Oscillation (AMO) generally do not.

Author affiliations: UVA Department of Environmental Sciences

10:45-11:00 am Understanding Southern Ocean cloud controlling factors on daily timescales and their connections to midlatitude weather systems. Mitchell Kelleher and Kevin Grise
Clouds and their associated radiative effects, important to understanding Earth’s energy budget, are one of the largest sources of uncertainty in global climate models. Constraining model simulation of clouds to better represent Earth’s radiative budget is thus important in constraining estimates of equilibrium climate sensitivity. One region with particularly large model biases in shortwave cloud radiative effects (CRE) is the Southern Ocean. Previous research has shown that many dynamic “cloud controlling factors” influence shortwave (solar) CRE on monthly timescales, and that two important cloud controlling factors over the Southern Ocean are mid-tropospheric vertical velocity and estimated inversion strength (EIS). Model errors may thus arise from biases in representing cloud controlling factors (atmospheric dynamics), representing how clouds respond to those cloud controlling factors (cloud parametrizations), or some combination thereof. This study extends previous work by examining cloud controlling factors over the Southern Ocean on daily timescales in both observations and global climate models. This allows the cloud controlling factors to be examined in the context of transient weather systems. Composites of EIS and mid-tropospheric vertical velocity are constructed around extratropical cyclones and anticyclones to examine how the different dynamic cloud controlling factors influence shortwave CRE around midlatitude weather in observations and models. Models tend to produce a realistic cyclone and anticyclone in terms of the dynamic cloud controlling factors. The difference between observations and models instead lies in how the models’ shortwave CRE responds to the dynamical cloud controlling factors, leading to bias in the model radiative shortwave CRE composites.

Author affiliations: UVA Department of Environmental Sciences

11:00-11:15 am Assessing air pollutant exposure inequities using novel high-resolution nitrogen dioxide airborne remote sensing observations in Houston, Texas. Mary Angelique G. Demetillo1, Katherine Knowles1, Aracely Navarro2, Jeffrey Geddes3, Caroline R. Nowlan4, Laura Margaret Judd5, Jassim A. Al-Saadi6, Sally E. Pusede1
More than 100 million people in the United States live in cities where air pollutant concentrations exceed standards designated to protect human health. While air quality has improved over the last few decades, there is evidence that pollutant concentrations are highly variable within cities, leading to inequalities in pollutant exposure as a function of neighborhood demographics. Past health assessments have relied on coarsely-resolved satellite or sparse ground-based atmospheric measurements, which are unable to resolve the steep spatial gradients of short-lived reactive trace gases, such as nitrogen dioxide (NO2), a pollutant regulated by the Clean Air Act and precursor to tropospheric ozone and fine-particulates. We use new high-resolution (hundreds of m2) NO¬2 observations collected by NASA’s airborne spectrometer, Geostationary Coastal and Air Pollution Events Airborne Simulator (GCAS), over Houston, Texas to (1) quantify community-level air pollution exposure burden inequities, (2) assess daily variability of community-level NO2 pollution burden and (3) investigate potential of space-based monitoring for environmental justice research. Results show the highest disparities in exposure as a function race-ethnicity and income to date, with lower-income, nonwhite communities experiencing 70% greater NO2 than high-income nonwhite communities. We also find non-white communities are exposed to 65% higher NO2 independent of income. We discuss time-of-day and day-to-day variability in these estimates. We also find that TROPOspheric Monitoring Instrument (TROPOMI) and forthcoming Tropospheric Emissions: Monitoring Pollution (TEMPO) have sufficient spatial resolution to monitor relative differences of community-level air pollution injustice, comparable to airborne measurements.

Author affiliations: 1UVA Department of Environmental Sciences, 2Colorado College, 3Boston University, 4Harvard-Smithsonian Center for Astrophysics, 5Universities Space Research Association Columbia, 6NASA Langley Research Center

11:15-11:30 am Impacts of air pollution on pheromone mediate mate-location in the hawkmoth Manduca sexta. Brynn Cook1, Markus Knaden2, T'ai Roulston3
Impacts of air pollution on pheromone mediate mate-location in the hawkmoth Manduca sexta.
Abstract: Sexual reproduction is a proven evolutionary strategy. To reap the benefits of sexual reproduction however, organisms must first overcome the challenge of locating a mate. In many animal species, mate location is mediated by sex-pheromones. Sex pheromones are species-specific chemical identifiers that are emitted by one partner, and can travel downwind over long distances, communicating both the identity and location of the calling partner to a conspecific. However, anthropogenically elevated atmospheric oxidants could interfere with sex-pheromone signaling by reacting with the pheromone compounds as they move through the atmosphere. Here, we demonstrate that key pheromone compounds used by the moth Manduca sexta are altered by the atmospheric oxidant ozone. Furthermore, male M. sexta find ozone-altered pheromone plumes less attractive, and perceive ozone-altered plumes differently in the antennal lobe, the first-order processing unit of the brain..

Author affiliations: 1UVA Environmental Science, 2Max Planck Institute, 3Blandy Experimental Farm

11:30-11:45 am Time vs. Space: Comparing Early Warning Indicators of Algal Blooms. Cal Buelo1, Mike Pace1, Steve Carpenter2
Aquatic ecosystems can undergo regime shifts between clear-water and algal dominated states where algal blooms are persistent or cycling. Based on dynamical systems theory, statistical indicators may provide early warnings prior to the development of blooms. These indicators include variance and autocorrelation in temporal and spatial data that change predictably near thresholds. In this study, we compared spatial and temporal indicators using a spatially explicit (2D) model that included both physical and biological processes. We simulated a planktonic system with increasing nutrient inputs that approached and eventually passed two critical transitions: 1) from a low-algae stable state to a cycling bloom state, and 2) from the cycling bloom state to a high-algae stable bloom state. We found that spatial early warning indicators, calculated from algal abundance across the entire system, provided clearer signals of the low nutrient loading transition than the high nutrient loading transition. Temporal early warnings, calculated from time-series of algal abundance at a single location, were less clear for the low nutrient input transition than the high input transition. Our findings suggest that both temporal and spatial statistics can foreshadow critical transitions in bloom state. Spatial and temporal approaches should be considered and where possible combined in future field studies and experiments that test the efficacy of early warning approaches..

Author affiliations: 1UVA Department of Environmental Sciences, 2University of Wisconsin Center for Limnology

Lunch: 11:45 am – 1:15pm

Odum Room, Clark Hall


1:15-2:30pm // Clark Hall // Room 133

1:15-1:30 pm Lobster Search in Turbulent Odor Plumes. Brenden Michaelis
Animals often use their sense of smell to locate food, identify mates and predators, and find suitable living habitats. Odor molecules are often dispersed from their source by turbulent wind or water currents. In both terrestrial and aquatic environments, the instantaneous temporal and spatial distribution of odors is complex, and odor plumes are often composed of filaments of chemicals at high concentrations that are adjacent to fluid with little or no odor. Navigation in turbulent chemical plumes has typically been considered a spatial information problem where individuals aim to path towards higher concentration. Concentration information alone is too irregular in turbulent plumes, particularly in water, to explain search speed and accuracy of many animals that undergo search. Recent discoveries of bursting olfactory neurons in the spiny lobster, Panulirus argus, suggest a mechanism for accurately sampling the temporal structure of chemical signals. We believe that considering the temporal element of chemical cues, such as intermittency encoding, is necessary to provide plume information on time scales relevant for informing efficient search behavior. Lobster pathing was analyzed in small scale flume experiments, using planar induced fluorescence, to measure the intermittent temporal signal encountered by searching lobsters as they navigate in a turbulent odor plume towards a source of food. Reactions to the intermittent signal are compared by analyzing changes in search speed and trajectory in response to frequency and intensity of the encountered stimulus.

Author affiliations: UVA Department of Environmental Sciences

1:30-1:45 pm Oyster Reef Activity Investigated using a Novel combination of bioacoustics and Aquatic Eddy Covariance Flux Measurements. Martin P. Volaric1, Eli M. Stine1, Peter Berg1, Matthew A. Reidenbach1, Olivia Caretti2
Oyster reefs are complex communities that exist against the backdrop of a dynamic physical environment. These ecosystems provide habitat to a wide variety of organisms that both generate noise and consume and release oxygen, resulting in complex soundscape and oxygen flux dynamics over tidal and diurnal cycles. In this study we paired continuous 24 – 48 h sound recordings with non-invasive in situ aquatic eddy covariance oxygen flux measurements in order to quantify how the activity of two intertidal Crassostrea virginica reefs on the Virginia (USA) coast varied over these short-term timescales. We made additional laboratory sound measurements of oyster valve closings, and were able to identify this sound in our field recordings. Preliminary results indicate that light and flow speed are important drivers of reef oxygen flux, while tidal stage is the major driver of the soundscape. The rate of oyster valve closings was highest at the beginning and end of each period of reef inundation, and was negatively correlated to oxygen uptake. Our results show that oyster pumping is likely greatest during peak high tide periods, which has important implications for oyster behavior and water column clearance rates.

Author affiliations: 1UVA Department of Environmental Sciences, 2North Carolina State University

1:45-2:00 pm Geomorphology Exerts Bottom-Up Control on Intertidal Macroalgae. Alice Besterman, Michael L. Pace
Intertidal flats are abundant ecosystems found in low-energy, coastal environments. Since these systems are considered an intermediate “state” between saltmarsh and subtidal lagoon, substantial research has addressed physical drivers of state transitions for tidal flats. However, tidal flats are themselves variable in morphology both within and between ecosystems, and these patterns are less well described. For example, intertidal flats can exhibit highly homogeneous or heterogeneous bedforms; in the latter case elevation changes dramatically over short horizontal distances (“hummocky” morphology). Further, qualitative observations, and some individual species distributions, suggest unique food web patterns may be correlated with different bedform patterns. Consequently, cross-scale drivers may result in patchy autotroph biomass. We measured physical variables that describe tidal flat morphology, and then related those physical variables to macroalgal abundance. Using multivariate analyses we found grain size was an important driver of morphology, and that smaller grain sizes were associated with greater heterogeneity in morphology. Highly heterogeneous flats (“hummocky”) had more sediment organic matter, and less macroalgal biomass. As sea-level continues to rise it will be important to understand how intertidal flat morphologies vary, what physical variables drive changes in morphology, and how those patterns relate to ecological function in coastal landscapes.

Author affiliations: UVA Department of Environmental Sciences

2:00-2:15 pm Decreasing pH negatively impacts stage Z1 Atlantic blue crabs, Callinectes sapidus. Christina Fantasia
As carbon dioxide continues to accumulate in the largest inorganic carbon sink, the oceans, its impact on biota within those systems cannot be ignored. Certain organisms such as pteropods and coccolithophores (Orr et al. 2005; Riebesell et al. 2000) show increased mortality across all life stages whereas other organisms experience sub-lethal effects such as reduced growth, delayed development, modified behaviors, and have thinner calcium carbonate based shells (Giltz & Taylor 2017; Long et al. 2013). In the Chesapeake Bay regional economy, the commercially valuable Eastern oyster (Crassostrea virginica) has exhibited sensitivity to increased acidity, but a second valuable fishery, the Atlantic blue crab, has had limited research on the impacts of decreasing pH on its early life stages. Only one other study has been conducted, on a Louisiana population, of early life stage blue crabs. That study found increased mortality and reduction in size after 9 day exposure to 7.8 pH (Giltz & Taylor 2017). This study sought to determine if there were increased lethal effects in stage Z1 blue crabs after exposure to acidic conditions of 6.8 and 7.4 pH compared to control tanks at 8.1 pH. Sub-lethal effects in morphology are more nuanced, but some negative consequences were observed. Further analysis of physiology, total protein, total lipids, and shell composition are planned.

Author affiliations: UVA Department of Environmental Sciences

2:15-2:30 pm The effects of thermal stress and sulfide toxicity on seagrass resilience in a Virginia Coastal Bay. Amelie Berger, Peter Berg, Karen McGlathery
Seagrass meadows are valued for the ecosystem services they provide, including blue carbon sequestration and storage. In response to recent worldwide seagrass declines, conservation efforts have emerged to protect, monitor, and restore seagrass habitats. Understanding the resilience of seagrass meadows is key to the successful restoration of ecosystem services. A recent eelgrass (Zostera marina) die-off event in one of the coastal bays of the Virginia Coast Reserve Long Term Ecological Research (VCR-LTER) site provides an unprecedented opportunity to study the recovery and resilience of seagrass habitats. This seagrass meadow is part of a landscape-scale restoration project at the VCR LTER that started in 2001. The meadow expanded and thrived until summer 2015, when field observations indicated a dramatic decline in seagrass shoot density. This study uses high-resolution in situ water temperature data to investigate the potential effects of thermal stress on seagrass resilience at the VCR-LTER. Sulfur isotope analyses of seagrass tissue were also used to determine whether another stressor – sulfide toxicity – contributed to the die-off event in 2015. Preliminary data suggest seagrass mortality was brought on by the synergistic effects of thermal stress and sulfide toxicity. Spatiotemporal differences in water temperature may also explain the heterogeneity of seagrass density observed throughout the meadow during the recovery period from 2016-2018. The VCR LTER site is a model for temperate systems globally, and is an ideal natural laboratory to study the potential impact of warming oceans on seagrass resilience.

Author affiliations: UVA Department of Environmental Sciences


(15 min)


2:45-4:00pm // Clark Hall // Mural Room
(Alphabetically by Presenter Last Name)

Study of Nitrogen Efficiency In Hydroponics System versus Conventional Farming. Neha Awasthi, Shining Wang, James Galloway, Aaron Mills
Nitrogen is necessary for the growth of plants. However, a large amount of nitrogen is wasted through excess fertilizer and leads to negative effects on the environment. The goal of this study was to compare the nitrogen usage and efficiency of a hydroponics system to the efficiency of conventional farming. In this study, a hydroponic system was set up by Babylon Microfarms in the Fresh Food Company Dining Hall at the University of Virginia. The system contained eight trays of lettuce which were monitored throughout the semester and the amount of nutrients entered into the system was recorded. The lettuce incurred nitrogen losses to the environment from the nitrate used in the solution and the nitrogen emitted through fossils fuels from the electricity powering the system. The total nitrogen used to grow the lettuce was 13.5 grams (10 g from the growth solution and 3.5 g from the light emission). There was 3.5 grams of nitrogen in the harvested lettuce and a virtual nitrogen factor (VNF) of 2.9 was calculated. Conventional farming on the other hand has a VNF of 5.1, almost double the VNF of the hydroponic system. That means that for every gram of lettuce consumed, 2.9 g was lost to the environment in a hydroponic system while 5.1 grams was lost to the environment in conventional farming.

Author affiliations: UVA Department of Environmental Sciences

The Effect of Hurricanes on the Monthly Anomalies of pH and Dissolved Inorganic Carbon at the Bermuda Atlantic Time-series Study site. Kira Baugh, Hyewon Kim, Scott Doney
Ecological processes have shown sensitive responses to changes in marine carbonate chemistry (e.g., dissolved inorganic carbon (DIC) concentration and pH levels). Through water-column mixing via strong winds, hurricanes can introduce the changes in marine carbonate chemistry and possibly accelerate the process of ocean acidification. Initially, I hypothesized that pH levels and DIC concentration fluxes were linked to hurricane activity, given that colder water introduced from deep water due to hurricanes can absorb more CO_2 from the atmosphere. DIC and pH data collected from the Bermuda Atlantic Time-series Study site, located in the Sargasso Sea (31°40’N, 64°10’W), was analyzed in conjunction with historic hurricane track records to test this hypothesis. The results showed that hurricanes were linked to pH and DIC anomalies. Specifically, hurricanes were associated with a decrease in pH and an increase in DIC concentration (i.e., ocean acidification). In 7 out of the 12 of the cases examined, hurricanes caused a decrease in ocean pH, and in 8 of the 12 of the cases, hurricanes caused an increase in DIC concentration. The effects that hurricanes have on pH levels and DIC concentration indicate that hurricanes can negatively affect ocean ecosystems. As waters continue to warm and major hurricanes become more frequent, ecological processes may become even more vulnerable to climate change.

Author affiliations: UVA Department of Environmental Sciences

The Practice of Dendrochronology for Trees in Tropical Regions. Jordan Chapman
This study focuses on examining the impacts of environmental factors such as average temperature and rainfall on the development of tree rings in deciduous tree species found in a tropical rainforest setting in Madagascar. Approximately 10 years worth of climate data exists for conducting analysis and to provide a medium for comparison. Over 300 different samples have been collected from the region from both deciduous tree species and tropical pines. Annual growth rings are in the processes of being counted, detrended and compared in order to understand the influences which climatic variations exert. This application of dendrochronology will hopefully result in a better understanding of the tree growth dynamics in an ecosystem where they are poorly understood relative to temperate forests. By revealing how past climate patterns shaped growth processes, this study additionally has the goal of quantifying what the expected effects of climate change and associated prolonged periods of drought will be on the rainforests of Madagascar.

Author affiliations: UVA Department of Environmental Sciences

Examining Tree Phenology Using Drone Based Aerial Images. Bailey Costello and Xi Yang
The study of phenology has historic context, but it is especially important today as a result of climate change. Leaf-out and senescence events are shifting temporally, which has ramifications for the water cycle, carbon cycle, plant-animal interactions, and industry. Observing tree phenology can help us build models in order to predict future changes in phenology resulting from warmer temperatures. There are several methods used to monitor tree phenology such as field observations, satellite data, and phenocams. However, these methods have spatial, temporal, and resolution based limitations. In this study, images of a forest section in Virginia are taken using a digital camera attached to a lightweight drone. The images, collected twice a week during the fall and spring and once a week during the summer, are stitched together to create orthomosaics. After calculating the relative greenness, measured as the Green Chromatic Coordinate, for individual trees, it is hypothesized that the timing of leaf-out and senescence events can be determined on the individual tree scale. The findings could have implications for intra-forest variability as well as the effectiveness of drone based remote sensing.

Author affiliations: UVA Department of Environmental Sciences

Observing severe drought influences on ozone air pollution in Central California. Mary Angelique G. Demetillo1, Jaime F. Anderson1, Jeffrey A. Geddes2, Xi Yang1, Emily Y. Najacht3, Solianna A. Herrera1, Kyle M. Kabasares4, Alexander E. Kotsakis5, Manuel T. Lerdau1,6, and Sally E. Pusede1
Drought conditions affect ozone air quality, potentially altering multiple terms in the O3mass balance equation. We present a multiyear observational analysis using data collected before, during, and after the record-breaking California drought (2011–2015) at O3-polluted locations in Fresno and Bakersfield near the Sierra Nevada foothills. We separately assess drought influences on O3chemical production (PO3) from O3concentration. We show that isoprene concentrations, which are a source of O3-forming organic reactivity, were relatively insensitive to early drought conditions, but decreased by more than 50% during the most severe drought years (2014–2015), with recovery as a function of location. We find drought-isoprene effects are temperature dependent, even after accounting for changes in leaf area, consistent with laboratory studies but not previously observed with atmospheric observations at landscape scales. Drought-driven decreases in organic reactivity are cotemporaneous with a change in dominant oxidation mechanisms, with PO3becoming more NOx-suppressed, leading to a decrease in PO3of ~20%. We infer reductions in atmospheric O3loss of ~15%during the most severe drought period, consistent with past observations of decreases in O3uptake by plants.

Author affiliations: 1UVA Department of Environmental Sciences 2Department of Earth and Environment, Boston University, 3Department of Chemistry, Saint Mary’s College 4Department of Physics, University of California Irvine 5Department of Earth and Atmospheric Sciences, University of Houston 6Department of Biology, University of Virginia

The effect of salt marsh geomorphologic classification on rates of transgression. Jessica A. Flester, Linda K. Blum, John H. Porter, Arthur C. Schwarzschild
Transgression was measured in nine Virginia sea-side, mainland salt marshes of three geomorphologic types: headland, hammock, and drowned river valley. Rates and areas of transgression were determined using ArcGIS and aerial photography taken in 2002 and 2017. The total area of marsh created at the upland boundary at each site ranged from 0.11 ha to 2.01 ha. Rates of transgression ranged one order of magnitude from 4.56 x 10-6 ha per m of upland boundary per yr (ha m-1 yr-1) to 4.50 x 10-5 ha m-1 yr-1. Hammock marshes showed the slowest rate of transgression by an order of magnitude compared to the other two marsh geomorphologic types. Headland marshes showed the highest rates of transgression (2.46 – 4.50 x 10-5 ha m-1 yr-1), followed by drowned river valley marshes (1.15-1.64 x 10-5 ha m-1 yr-1), and hammock marshes (4.56-7.07 x 10-6 ha m-1 yr-1). These results are consistent with the literature as previous studies have predicted that headland marshes would show the highest rates of transgression because they are directly adjacent to lagoonal systems with direct exposure to waves and long fetch, whereas hammock marshes and river valley marshes are afforded some level of protection from adjacent lagoons.

Author affiliations: UVA Department of Environmental Sciences

Quantifying and mapping oyster reefs utilizing LiDAR -based remote sensing. Sara Hogan and Matthew Reidenbach
Within the Virginia Coast Reserve (VCR) on the Eastern Shore of Virginia, efforts are underway to restore populations of the eastern oyster, Crassostrea virginica. It is necessary to identify and understand the distributions of oysters and suitable environments to inform future restoration projects. Here we determine if light detecting and ranging (LiDAR) derived data can be used to classify land cover within intertidal regions of the VCR. We also use the locations of existing patches to determine characteristics of suitable oyster habitat using elevation, fetch (as a proxy for wave energy), and water residence time data. It was found that oyster patches mapped using LiDAR-based elevation data overlapped greater than 90% with in-situ GPS ground-truth data. Trained with elevation, intensity, surface slope, and curvature data, the land cover classification was able to identify oyster cover with an accuracy greater than 80 %. Ground-truth patches were found to in a narrow range of elevation (-0.5 to -0.1 m relative NAVD88) and relief from surrounding land (0.15 – 0.87 m). The suitability analysis located 10.9 km2 of total suitable habitat within the VCR that contained similar elevation, fetch, and residence time characteristics of existing reef area, and habitat was most restricted by elevation. The suitability map indicates there is still area available to promote oyster growth which should be targeted for future restoration efforts.

Author affiliations: UVA Department of Environmental Sciences

Assessment of nutrient concentration and availability in ice-wedge polygon successional stages in a coastal Arctic tussock tundra in Jago, Alaska. Kelcy Kent and Howard Epstein
Nitrogen availability strongly influences plant productivity and distribution in Arctic environments. Recently, the Arctic has experienced warmer temperatures and the resulting permafrost thaw along the coastal Arctic tundra has caused ground subsidence, ponding, and the release of solutes and nutrients, impacting vegetation distribution. In patterned ground (polygon) permafrost systems, nutrient cycling can vary substantially across ice-wedge polygon successional stages. A better understanding of fine-scale spatial and temporal nutrient cycling among these ice-wedge polygon trajectories will improve the ability to predict tundra response to warming. This study took place during July and August of 2018 in a coastal tussock tundra site in Jago, Alaska. The study aims to identify and quantify plant-available inorganic nitrogen and total dissolved nitrogen in the soil, water tracks, and ponds of various successional stages of ice-wedge polygons, and to quantify %N and C:N ratios in plant biomass in each successional stage. Water samples were taken from various inundated or water-logged ice-wedge polygon successional stages and water tracks flowing throughout the transect, and NO3- and NH4+ uptake in each site type were assessed with buried bag experiments and AgWestern ion probes. Biomass was clipped from each successional stage to compare functional group composition, mass, and C:N ratios. Clippings of the common tussock-forming sedge Eriophorum angustifolium was also taken from each successional stage to use as a benchmark species to compare C:N ratios across site types. Preliminary results show that though there are relatively small concentrations of NH4+, and especially NO3-, at all sites sampled, there is a greater availability of NH4+ and total dissolved nitrogen in sites that are experiencing some form of degradation and are waterlogged or inundated. This suggests that thaw and ponding may increase N availability to plants. Though the AgWestern ion probes suggest greater N uptake rates at sites experiencing some form of degradation, C:N ratios of E. angustifolium appear relatively consistent across sites. Future work includes completing the assessment of the buried bag experiments to compare with the data from the AgWestern ion probes; analysis of biomass clippings from each ice wedge polygon successional stage for vegetation functional group composition, mass, and C:N ratios; and further studying nutrient availability in relation to ice-wedge degradation or stabilization and the impending effect on Arctic tundra vegetation in additional sites in the coastal Arctic tundra.

Author affiliations: UVA Department of Environmental Sciences

Data assimilative modeling of marine ecosystem and microbial dynamics in the coastal West Antarctic Peninsula. Hyewon Kim1, Ya-Wei Luo2, Hugh W. Ducklow3, Oscar M. Schofield4, Deborah K. Steinberg5, Scott C. Doney1
The coastal West Antarctic Peninsula is a rapidly warming ecosystem, with observed responses of marine ecosystem processes to changing physical forcing. To explore ecological and microbial responses to changing environments through carbon flows mediated via complex marine food-web interactions, we developed a one-dimensional data assimilative ecosystem model based on a variational adjoint scheme. By assimilating eleven different biological data types from Palmer Long-Term Ecological Research observations and optimizing model parameters, the data assimilation scheme significantly minimized model-observation misfit and reached a local cost function minimum for each growth season analyzed. Overall, optimized model solutions presented a better performance in simulating bacterial dynamics while they also appropriately captured the dynamics of unassimilated data type (e.g. zooplankton). Despite significantly different physical forcing for each modeled growth season, key ecosystem and microbial indices (i.e. carbon export and bacterial production to net primary production or NPP ratios) presented little year-to-year variability as a result of balanced intercompartmental flows dictated by different trophic mechanisms. Those key ecosystem and microbial indices also indicated that all three years were more characterized by microbial food-webs. Numerical experiments with temperature perturbations revealed that bacterial processes were likely suppressed by low temperatures for some growth seasons and that NPP and carbon export may decrease while bacterial activity may be promoted under future ocean warming scenarios.

Author affiliations: 1Department of Environmental Sciences, University of Virginia, 2State Key Laboratory of Marine Environmental Science, Xiamen University 3Lamont-Doherty Earth Observatory, Columbia University, 4Department of Marine and Coastal Sciences, Rutgers University, 5Virginia Institute of Marine Science

Assessing Acid Deposition as a Control on Forest Productivity and Water Use. Jacob Malcomb1, Todd Scanlon1, Howie Epstein1, Daniel Druckenbrod4, Matthew Vadebonceour2, Lixin Wang3, Matthew Lanning3
The Clean Air Act and its amendments have resulted in substantial declines in deposition of acidic nitrogen and sulfur compounds over the forests of the eastern United States. Recent studies have attributed increases in forest water use efficiency (WUE) — the ratio of forest primary productivity to water lost via transpiration — to changes in acid deposition, but the underlying mechanisms remain poorly understood. We examined environmental controls on tree aboveground net primary production (ANPPstem) and water use efficiency in a watershed subjected to 26 years of acidification treatments, and in an adjacent control catchment, at the Fernow Experimental Forest in West Virginia. ANPPstem was greater for three of four species in the untreated catchment, implying that acid deposition is a negative control on tree growth. Notably, three species in the treated catchment were less sensitive to water availability, suggesting that acid deposition may alter tree response to climate. WUE was calculated as the ratio of aboveground primary productivity (derived from tree ring and forest inventory data) to catchment evapotranspiration. WUE did not differ between watersheds, but this result may be partially attributable to the dominance of black cherry, an acid-tolerant species, in the treated catchment. These results suggest that assessment of whole-forest response to acid deposition should consider tree species composition.

Author affiliations: 1UVA Department of Environmental Sciences, 2University of New Hampshire, 3IUPUI, 4Rider University

Comparing the Diurnal Cycles of Column Averaged and Surface CO2 in Park Falls, WI. Kayla Mitchell
In general atmospheric circulation models of CO2, vertical transport of CO2 through a column is an area of some uncertainty. Characterizing the diurnal cycle of column averaged CO2 and comparing it to that of surface CO2 helps determine the strength of vertical mixing between the free troposphere and atmospheric boundary layer. Column averaged CO2 measurements from TCCON’s site in Park Falls Wisconsin are compared to Park Falls surface CO2 measurements from NOAA’s flask network. Data from 2005 to 2011 are filtered, manipulated, and plotted using Matlab. Diurnal CO2 variability between column averaged and surface CO2 is qualitatively analyzed using a series of visual representations and quantitatively analyzed using statistical analysis. Trends and discrepancies between surface and column CO2 are interpreted through economic, ecologic, and atmospheric lenses. On average, diurnal variability is lower in column averaged CO2 than surface CO2 and higher in July than January. Increased uptake of CO2 by photosynthesis in the summer is evident in lower summer CO2 averages and an observable annual cycle each year. Less photosynthesis, less respiration, and a shallower boundary layer could explain reduced winter diurnal variability in both surface and column CO2. Column and surface CO2 diurnal variability behave most differently in July, suggesting less vertical/horizontal mixing, more temperature inversions, and a more stable summer atmosphere in Park Falls, WI.

Author affiliations: UVA Department of Environmental Sciences

How Busy can a Bee Be? Exploring Whether Native or Exotic Flora Influence Bumble Bee Foraging Efficiency and Colony Success. Sophia M. Rosenberg1 and David E. Carr1,2
Habitat loss is an important factor in the decline of native bumble bees. Habitat restorations have positive effects on wild bee abundance and diversity, but the effects of these efforts on individual colonies is not well documented. In this study, we documented 1) the abundance of floral species in both fallow and restored warm season grass fields, 2) diurnal variation in pollen resource availability, and 3) the effects of floral resource availability on the foraging efficiency and success of experimental Bombus impatiens colonies. We found there was no significant difference of total floral density between the warm season and fallow fields, but native species were at significantly higher densities in warm season grass fields. Most species experienced significant pollen depletion between the morning and afternoon. The rate of pollen return and the proportion of bees with pollen returning to colonies did not differ significantly between warm season and fallow fields. Higher abundance of Penstemon digitalis and Securigera varia significantly increased the rate at which bees came into the hive with pollen and significantly increased the proportion of bees returning with pollen. Conversely, bees returned to the hive with pollen at a significantly slower rate with increasing abundance of Carduus. The rate at which pollen entered the colony had no effect on bee body size or total brood production. Our results ultimately revealed no consistent differences between warm season and fallow fields, but a small number of species play an outsized role as pollen resources for bumble bees.

Author affiliations: 1UVA Department of Environmental Sciences, 2Blandy Experimental Farm

I know what you did last summer: Foraging in Bombus griseocollis (Hymenoptera: Apidae) as revealed by motion capture video technology. Amber Slatosky
The majority of detailed studies regarding colony-wide individual foraging in Bombus (Hymenoptera: Apidae) use commercially-reared bumble bees that produce large colonies of small workers (B. impatiens). Fewer studies examine the foraging patterns of bumble bees that produce fewer, large workers such as B. griseocollis. Past research has shown that bumble bees carrying conopid fly larvae (Diptera: Conopidae) are less likely to carry pollen and are more likely to spend time away from the colony. This work explores activities of parasitized and unparasitized individuals in two B. griseocollis colonies: time spent foraging, overnighting behavior, and pollen return. These activities were passively observed by using a Raspberry Pi computer and camera module with motion capture software and later reviewed for data collection (a unit and imagery will be available for viewing). Results for B. griseocollis suggest that conopid flies impact foraging in different ways for different species. Also reported are: rates of pollen return, pollen color, pollen load size, and a sampling of individual bee foraging behaviors over the experimental period.

Author affiliations: UVA Department of Environmental Sciences

A comparison of modeled and observed CO2 species variability in the North Atlantic near Bermuda during 1988-2009. Xi Wu and Scott Doney
The oceans have taken up approximately 25% of anthropogenic CO2 emissions since the industrial revolution, playing an important role in controlling the atmospheric CO2 levels. We analyzed over 20-year (1988-2009) global climate model (CESM1) output of monthly CO2 species and relevant physical and biological variables at the Bermuda Atlantic Time-series Study (BATS; 31°40’N, 64°10’W) site in the North Atlantic. The model output of sea surface temperature (SST), mixed layer depth and surface partial pressure of CO2 (pCO2) fit well with the observed data, whereas the salinity, dissolved inorganic carbon (DIC), Alkalinity (Alk), salinity normalized DIC (nDIC) and Alk (nAlk) in surface seawater were underestimated by the model, which might be caused by terristrial carbon and weathering inputs from rivers that are not included in the model. The model underestimated the magnitude of the seasonal cycle for those variables but captured the phasing overall. In summer, high temperature decreased the solubility of CO2 and increased pCO2; meanwhile, strong photosynthesis absorbed CO2 and lowered DIC and pCO2, and vice versa in winter. In this case, both modeled and observed surface pCO2 showed maximum values in summer and minimum values in winter, which illustrated temperature dominated the seasonal cycle of pCO2. Alk were not quite affected by temperature and photosynthesis and did not show significant seasonal variations. The model well captured the observed increasing long-term trends of seasonally detrended CO2 species resulting from the continual uptake of anthropogenic CO2. Overall, the model did an acceptable job at simulating CO2 species variability at BATS.

Author affiliations: 1UVA Department of Environmental Sciences, 2College of Chemistry and Chemical Engineering, Ocean University of China

The effects of winds on sediment dynamics in South Bay, VCR. Qingguang Zhu and Patricia Wiberg
Seagrass meadows adjacent to marshes have the potential to affect sediment delivery and wave energy, and thus influence state change of adjacent marshes. As an important parameter representing the sediment supply capability to these systems, suspended sediment concentration (SSC) is highly variable in response to tidal and storm forcing. We recorded SSC, tides, waves and collected seabed surface samples at 3 sites on a marsh and adjacent water body in South Bay, Virginia Coast Reserve (VCR). We find that sediment in seagrass meadow is finer than bare flat and marsh, and the responses of significant wave height and SSC are different between seagrass meadow and bare flat.

Author affiliations: UVA Department of Environmental Sciences

Keynote Address. DR. PATRICIA YAGER

4:00-4:50pm // Clark Hall // Room 107
Expand to view abstract.

Melting ice sheets impact more than sea level. The Amundsen Sea polynya (Antarctica) is a biological oasis that is the greenest place in all of the coastal Southern Ocean. It is also a large sink for atmospheric carbon dioxide. The region supports krill, snow petrels, penguins, crabeater seals, orca whales, minke whales, and many other species. This ecosystem richness has been linked to the nearby melting glaciers. Our multidisciplinary effort aims to understand the processes and mechanisms behind this link. We find that when warm, deep ocean water interacts with the base of an ice shelf, the meltwater triggers a buoyant upwelling of seawater rich in fertilizer for coastal plankton, triggering a massive bloom. The bloom also depends on light, however, tightly coupling productivity to the seasonal sea ice zone, which is also disappearing. Our goal is to better understand how this important ecosystem will respond to additional climate change.

Author affiliations: University of Georgia, Department of Marine Sciences

Closing Remarks.

4:50-5:00Pm // Clark Hall // Room 107


5:00-6:30pm // Clark Hall // Odum Room


Photo Credit:
Jake Malcomb
PhD Student of Ecology
Advisor: Howie Epstein

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