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David Buchwalter


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Date: 04/01/19 - 3/31/23
Amount: $352,782.00
Funding Agencies: National Science Foundation (NSF)

Overview: The biodiversity of freshwater ecosystems is typically dominated by aquatic insects. These insects evolved from terrestrial ancestors and have unique physiological characteristics that differ from other freshwater taxa (fish, crustaceans, molluscs) that evolved from marine ancestors. It has become clear that salinity plays a major role in shaping where species can live. Very few insects have successfully invaded marine environments, and when freshwaters become saltier, profound biodiversity losses are observed. It has been a challenge to understand the physiological basis for these observations because laboratory models for obligate freshwater insect species did not exist until very recently. The Buchwalter lab has been instrumental in developing a lab-reared mayfly – Neocloeon triangulifer as a promising laboratory model organism. This project combines several physiological approaches in this new model organism (ion uptake rate studies using radiotracers, respirometry, gene expression) with comparative studies to better understand the energetic basis for how and why performance of aquatic insects varies with transport rates of major ions. The project capitalizes on ecological niche models that provide hypotheses about how salinity contributes to determining where different species can live. The project uses these models to select species for phylogenetically informed comparative experiments to link physiological traits to species distributions in nature. Intellectual Merit: This project will reveal for the first time how the transport rates of major ions (Na+, Ca++, SO4-2) vary with developmental stage, metabolic rates, and energetic status in an obligate freshwater insect. Because the thermal reaction norms of this species have just recently been established, it is now possible to explore the combined effects of salinity and thermal change to better understand how these abiotic factors combine to determine ecological niches. This unique interdisciplinary approach combining phylogenetically informed comparative physiology, community ecology and niche modeling will provide new insights into the physiological mechanisms that determine the spatial distribution of aquatic invertebrate species. The work will advance the fields of osmoregulatory physiology and invertebrate ecology from a basic science perspective. Additionally, this project will provide tools for monitoring and predicting the distribution of aquatic invertebrates and the impacts human salinization may have on biodiversity. Broader Impacts: This project will engage high school students by providing curricular materials and research experience for high school teachers through the Kenan Fellows ( program. Additionally, the project will increase the participation of underrepresented groups in science by providing well-paid summer research internships for students from Historically Black Colleges. The project will also provide a rich interdisciplinary training environment for both undergraduate and graduate students. Increases in salinity associated with land use and climate change will require that water resource managers possess the appropriate knowledge and tools to effectively manage this growing threat. The data we produce should greatly advance our ability to interpret biological response to salinity and other stressors. To rapidly improve the use and interpretation of this information, we will develop two outreach activities that targets water resource managers. First, we will revise the Western Monitoring Center’s web site ( (1) provide access to the field- and laboratory-derived salinity preference/tolerance estimates that we produce and (2) include pages that discuss appropriate use and interpretation of these data. Second, we will organize a 2-3 day workshop for water resource managers that will cover natural spatial and temporal variation in freshwater salinity regimes, patterns and causes of increasing salinization, and use of laboratory- and field-derived response signatu

Date: 02/28/20 - 1/31/22
Amount: $3,938,845.00
Funding Agencies: National Institutes of Health (NIH)

Per- and polyfluoroalkyl substances (PFAS) are emerging as a major public health problem in North Carolina and across the United States. PFAS comprise a class of over 5,000 compounds. Their unique chemical properties have been harnessed to make consumer and industrial products more water, stain, and grease resistant; they are found in products as diverse as cosmetics and flame-retardants. PFAS are resistant to degradation, move easily through the environment, and accumulate in living organisms. Exposure to PFAS has been associated with health effects including cancer and toxicity to the liver, reproductive development, and thyroid and immune systems. Despite widespread detection in the environment and evidence of increasing human exposure, understanding about PFAS toxicity, its bioaccumulative potential in dietary sources such as aquatic organisms, and effective remediation remain notably understudied. The recent discovery by this proposed Center’s Deputy Director, Dr. Detlef Knappe, of widespread PFAS contamination in the Cape Fear River watershed in NC underscores that these compounds are in need of immediate investigation.. The goal of our Center is to advance understanding about the environmental and health impacts of PFAS. To meet this goal we are employing a highly trans-disciplinary approach that will integrate leaders in diverse fields (epidemiology, environmental science and engineering, biology, toxicology, immunology, data science, and advanced analytics); all levels of biological organization (biomolecule, pathway, cell, tissue, organ, model organism, human, and human population); state-of-the-art analytical technologies; cutting-edge data science approaches; a recognized track record in interdisciplinary, environmental health science (EHS) training; and well-established partnerships with government and community stakeholders.

Date: 05/01/15 - 4/30/20
Amount: $390,974.00
Funding Agencies: National Science Foundation (NSF)

Freshwater ecosystems support a disproportionate percentage of earth’s biodiversity and are among the most threatened by human activities and global climate change in general and global warming in particular. Insects dominate fresh-water ecosystems in terms of biodiversity and ecological processes. Thus, many effects of global change and other anthropogenic activities on freshwater ecosystems will likely be manifested via thermal effects on aquatic insect performance (growth, survival, and reproduction). Temperature controls the developmental timing, species distributions, and community structure, but both the thermal limits of individual taxa and the underlying physiological mechanisms that determine those limits remain poorly understood. Thus we remain limited in our ability to predict how thermal variation shapes freshwater communities in space and time. The work proposed here takes major steps towards achieving our long-term goal of understanding how temperature drives the macro-ecology of aquatic insects by first linking rigorous, full life-cycle laboratory rearing experiments that quantify thermally-mediated life history outcomes/performance to physiological studies that define the mechanisms underlying those life history outcomes. We focus on thermal effects on energy allocation through integrated approaches (respirometry, calorimetry, molting frequency, gene expression) that ultimately tie physiological processes to fitness. Finally, we extend our physiological understanding to the macro level by determining if the physiological effects of temperature are consistent with the predictions of empirical species distribution models (ESDMs).

Date: 04/01/16 - 12/31/18
Amount: $55,085.00
Funding Agencies: Electric Power Research Institute, Inc.

The primary objectives or our work are to beter understand the behavior (speciation and potential for biological uptake) of arsenic in aquatic food webs. Primary goals as as follows: 1. Assess the stability and rates of interconversion of arsenate and arsenite in water under different environmental conditions (dissolved oxygen, pH). These experiments are designed to understand how important abiotic arsenic species intervonversions are under different environmental conditions. 2. Assess the influence of pH on uptake kinetics of arsenate vs. arsenite into periphyton As uptake into periphyton is known to be influenced by a number of variables, including temperature, redox conditions, pH, and nutrient concentrations (e.g., P). This task is aimed at understanding how pH may differentially impact the uptake kinetics of arsenate versus arsenite into periphyton. 3. Compare the trophic availability of As from periphyton exposed to arsenate vs arsenite. Here we will determine whether As oxidation state in solution has any bearing on As bioavailablity from periphyton. 4. Compare the speciation of As in periphyton after exposure to arsenate vs arsenite using XANES. Aquatic primary producers are known be able to transform arsenic via oxidation, reduction, and methylation. These proceses have not investigated in periphyton. In addition, arsenic is known to associate with other elements based on oxidation state (e.g., AsV and Fe). The specific associations of arsentate vs. arsenite in periphyton may have important impliacations for trophic transfer.

Date: 07/01/16 - 6/30/17
Amount: $37,860.00
Funding Agencies: NCSU Center for Human Health and the Environment

Arsenic is a widespread environmental contaminant that poses risks to human health throughout the world. Engineered systems for the removal of arsenic from fast-flowing waters are currently unable to accommodate the dual needs of arsenic removal and water conveyance. This lack of technical capacity can lead to substantial release and exposure of hazardous quantities of arsenic, causing arsenic environmental health risks from settings as varied as Superfund sites in the US and rice production fields in Asia. The overall goal of our proposed work is to develop and test novel fabric-based technologies, which may be utilized within contaminated flowing-water streams, for removing arsenic from water. We hypothesize that surface-functionalized, arsenic -binding fabrics, in concert with ecological engineering measures, can provide a practical means for maximizing arsenic removal from contaminated water. Here, we will integrate textile-science, aqueous- and soil-chemistry, and ecological-engineering research to optimize selective arsenic-removal properties of surface-functionalized fabrics and quantify the removal rates and ultimate fate of arsenic within water-fabric systems. The proposed work will catalyze a new, interdisciplinary partnership among scientists with a unique set of expertise from CALS, COT, COS, and COE at NCSU. This research will also support ongoing efforts to develop larger proposals for NIEHS and NSF, and results will lead to potentially patentable technologies with wide-ranging implications for treating chemically contaminated water.

Date: 10/01/14 - 6/30/16
Amount: $203,151.00
Funding Agencies: Utah, State of

Concerns about water quality in the Great Salt Lake (Utah) have prompted the need to evaluate the toxicity of priority pollutants to the dominant invertebrate fauna of the lake. In support of this goal, toxicity tests will be performed for methyl mercury, ammonia, copper, arsenic and lead in two species - brine shrimp and brine flies.

Date: 03/01/15 - 2/28/16
Amount: $60,000.00
Funding Agencies: NCSU Water Resources Research Institute

The combustion of coal to meet demands for energy produces byproducts (“ash”) containing trace elements known to be toxic to fish, wildlife, and people. North Carolina ranks ninth among states in the annual generation of coal-derived ash. The recent spill of 39,000 tons of coal ash into the Dan River highlights the need to understand both the immediate and long-term impacts of trace element inputs at the base of aquatic food webs, which controls bioaccumulation in fish and higher organisms. The storage of another 102 million tons of ash in 33 basins throughout North Carolina is also of concern with regard to past and future releases of potentially toxic trace elements into ground and surface water resources. This project focuses on arsenic – one of the primary elements of concern related to coal ash. Arsenic is challenging because it exists in many forms that vary tremendously in their toxicity and bioavailability. As such, measurements of total arsenic in environmental media or biological tissues do not provide sufficient information to assess potential risk. Our research focuses on biological processes that play primary roles in determining the forms of arsenic present in the tissues of aquatic organisms. This project combines bioaccumulation and trophic transfer studies using radiotracers with detailed studies of arsenic speciation using X-ray Absorption Near Edge Structure (XANES) spectroscopy. This research spans different trophic levels (periphyton, invertebrates and fish) to explicitly assist in the interpretation of field monitoring efforts of the Dan River coal ash spill site.

Date: 10/01/13 - 12/31/14
Amount: $5,000.00
Funding Agencies: Society of Environmental Toxicology & Chemistry

As a 3rd year doctoral student in Dr. David Buchwalter’s laboratory at North Carolina State University, Ms. Poteat has developed a dissertation project that encompasses mechanistic studies of metal bioaccumulation and interactions in aquatic insects as well as comparative/evolutionary aspects of metal bioaccumulation in aquatic organisms. Because aquatic insects form the backbone of biomonitoring programs in the United States and are the most commonly used bioindicators of environmental quality in freshwater ecosystems, it is important to understand their underlying physiologies. Ultimately, Ms. Poteat is interested in identifying how and why insect species are differentially responsive to metals. She is applying evolutionary physiology perspectives to better understand and predict how metal bioaccumulation parameters vary within and among different faunal groups. Her ultimate goal is to test whether phylogenetic methods can be used to enable prediction and extrapolation of metal bioaccumulation/toxicity in aquatic communities. Overall, her work has the potential to improve water quality criteria development, risk assessment and bioassessment by combining mechanistic and comparative methods to predict metal sensitivity parameters for data-poor species and decreasing the need for resource-intensive in vivo testing.

Date: 06/01/13 - 12/31/14
Amount: $60,000.00
Funding Agencies: NCSU Water Resources Research Institute

The objectives of this proposed work are to understand the thermal and flow requirements of North Carolina aquatic macroinvertebrates. Macroinvertebrates are the primary faunal group used by the North Carolina Division of Water Quality in ecological monitoring programs because they predominate in aquatic ecosystems, and are responsive to environmental change. However, the scientific community lacks the ability to predict how communities will be altered due to changing thermal and flow regimes that result from human activities and predicted climate change. Both temperature and flow have the ability to directly affect respiration in water breathing species. This proposed research will use state-of-the-art respirometry techniques with carefully selected species to provide a major first step in giving resource managers the ability to predict which specific taxa are likely to be the most responsive to thermal and flow change.

Date: 08/29/11 - 6/30/14
Amount: $112,500.00
Funding Agencies: US Geological Survey (USGS)

As currently practiced, biomonitoring approaches are generally successful in determining whether or not systems are ecologically impaired. However, these approaches were not designed to allow end users to identify causes of impairment, or predict how a community might change in responses to stressors like temperature. Because we don?t understand why and how species are differentially responsive to elevated temperatures, we are limited in our ability to interpret species composition data in light of climate change. This limitation is pervasive, hampering programs at the local, state, and national levels where millions of dollars are spent annually. The primary objective of this program is to experimentally determine the thermal tolerance ranges for several key invertebrate species. These values will be compared to empirical derived values generated by USGS personnel in Tacoma WA. Aquatic insects are a key biomonitoring group because of their dominance in the total biodiversity found in a given habitat and their central role in ecosystem functioning. Further, as poikilotherms, insect growth, survival, and persistence at a site is highly temperature dependent. Thus, they are key ?sentinel? species to; 1) quantify (described herein), 2) monitor (done routinely in the northwest), and 3) indicate (product of this proposal) the effects of climate change. By combining a statistical description of critical (and therefore exploitable for prediction) temperature ranges in key species with laboratory testing of the thermal range of that same species, we seek to ?add value? to existing local, state and regional biomonitoring programs by developing species specific temperature tolerance values. These values can then be used by scientists and resource managers to predict locations and communities (based on their species assemblages) of greatest vulnerability to changing temperatures.

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