NSF Supported Ph.D. Assistantships now available. Please contact Dr. Buchwalter for details.

 

Contact Us

Mailing address:
Department of Environmental and Molecular Toxicology
Box 7633, NC State University
Raleigh, NC 27695-7633

Shipping address:
Suite 1104, 850 Main Campus Dr.
Raleigh, NC 27606

Phone 919.515.2274
Fax 919.515.7169

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

David Buchwalter, Ph.D.
Assistant Professor and Coordinator of Environmental Toxicology Concentration, Department of Environmental and Molecular Toxicology

 

Phone: 919-513-1129
E-mail: david_buchwalter@ncsu.edu

Education
BS, Zoology, University of Massachusetts, Amherst
MS, Toxicology, Oregon State University
PhD, Environmental and Molecular Toxicology, Oregon State University
Postdoctoral, NRC / US Geological Survey, Menlo Park, CA

 

Research Interests

● Ecotoxicology

●Environmental and evolutionary physiology

●Toxicity of metals and ions

●Trophic transfer/food web dynamics

●Aquatic insect osmoregulation and respiration

●Ecological indicators

 

The major themes that we explore in our lab are comparative invertebrate ecophysiology and trace metal bioaccumulation and detoxification. A major goal of our work is to better understand how and why species are differentially responsive to environmental stressors such as trace metals and other ions. We primarily work with field collected populations from both reference and contaminated ecosystems, though we are developing a mayfly (Centroptilum triangulifer) as a model organism.  We are particularly interested in the use of phylogenetic frameworks as a means of predicting a taxon's physiological performance.


Read a news story about our study published in the Proceedings of the National Academy of Sciences: Aquatic Insect 'Family Trees' Provide Clues About Sensitivity to Pollution: http://news.ncsu.edu/news/2008/06/098mkbuchwalterpnas.php

 

1) Comparative aquatic insect ecophysiology
How do species vary in physiological processes critical to their success in aquatic environments? Aquatic insects provide ideal models to study these basic questions because of their fascinating evolutionary histories. Aquatic insects are believed to be derived from terrestrial ancestors who invaded aquatic habitats several times over evolutionary history. As a result, they have developed a variety of solutions to the three major challenges associated with aquatic life: locomotion, respiration and osmoregulation. We are particularly interested in respiratory and osmoregulatory physiology as it relates to the accumulation of contaminants and responses to thermal stress. Current projects include the use radiotracers to measure fluxes of ions into and out of organisms (see below). We are also beginning to explore insect strategies (enzymatic and non-enzymatic) for dealing with oxidative stress. How much physiological variation exists within and among various insect lineages? Can phylogenetic position be a useful predictor of physiological performance?


2) Trace metal bioaccumulation and detoxification
All invertebrates accumulate trace metals in their tissues, but different species accumulate metals differently, even when they are in the same water. Differences in accumulation patterns can arise from different physiological traits including the propensity to accumulate metals directly from water, the assimilation of metals from their diets, and/or the ability to efflux metals from their tissues. We use radiotracers to examine these ecophysiological traits in different species to help understand why some species are so exquisitely sensitive to trace metal toxicity, while others are able to thrive in metal-polluted environments. A major challenge is to better understand the consequences of accumulated metals in different species, because species vary in their abilities to protect cells from oxidative damage via the sequestration of metals by metallothionein-like proteins, glutathione and other proteins. Furthermore, species vary in their abilities to evade oxidative damage resulting from metal exposures, by differential expression of antioxidative enzymes and non-enzymatic antioxidants.


3) Mercury dynamics in the environment
Mercury is a ubiquitous and highly toxic environmental pollutant. We are interested in indentifying factors, both biotic and abiotic, that are responsible for mercury accumulation in different environments and species. We use a Cold Vapor Atomic Fluorescence Spectrophotometer to measure Hg concentrations in various media including tissue samples.  We have performed Hg analyses for collaborators on a diversity of samples, including song bird feathers, black bear tissues, fish tissues, insects and sediments.


4) The use of insects as ecological indicators
The use of insects as indicators of ecological condition has a long and rich history. While biologists and ecologists can use insect communities to infer whether or not systems are ecologically impaired, the ability to use resident biota to determine the causes of this putative impairment remains elusive. Generalizations hinder the utility of many current bioassessment protocols. The use of a single tolerance value to describe a taxon's susceptibility to all stressors is a major problem in bioassessment today. Generalizations are also problematic with the lumping of broad taxonomic groups (e.g. "chironomids are tolerant" or "mayflies are sensitive"). These generalizations are pervasive in bioassessment today and need to be replaced by a more fundamental understanding of how and why certain species are responsive to environmental stressors. Work in our lab explores physiological traits in a phylogenetic context to better understand the mechanisms underlying sensitivity differences among taxa.


5). Development of a mayfly model for ecotoxicology and toxicogenetic studies
With collaborators at the Stroud Water Research Center, we are working to develop the mayfly Centroptilum triangulifer as a new model organism. This parthenogenic species is amenable to lab culture and is a promising test organism for life cycle assays. We have recently completed a large cDNA sequencing effort, and have identified numerous genes of toxicological interest.

 

Lab Personnel

Lingtian Xie, Ph.D, Postdoctoral Research Associate
Lingtian Xie obtained his Ph.D in Environmental and Evolutionary Biology from the University of Louisiana at Lafayette in 2002. He joined Dr. Buchwalter's lab in December 2005 as a Post-Doctoral Research Associate. His research focuses on responses of aquatic organisms to contaminants at different biological levels (population, organismal, biochemical, and molecular levels). His previous work focused on the evolution of resistance to contaminants in aquatic organisms, detoxification mechanisms, and fitness costs associated with evolution of resistance. He also studied the effects of endocrine disruption chemicals in fish (rainbow trout and Japanese medaka). He is currently working on the purification of metal-binding proteins in aquatic insects using HPLC/MS. His other interest includes determination of mercury levels in biological samples using cold vapor atomic fluorescence spectrophotometry.   Xie Publications

Beth Cable B. Cable
Beth obtained her BS in biochemistry from Miami University in Oxford, OH. She joined the Buchwalter lab as an MS student in fall 2008. Her work is part of an effort to understand the proximal stressors associated with ecological changes in mountaintop removal/valley fill coal mining impacted streams in the Appalachians. Beth’s work will include elemental analyses of field collected stream insects in addition to lab based work looking at manganese bioaccumulation from dissolved and dietary sources in aquatic insects.

Justin ConleyConley
Justin obtained his BS in Environmental Studies from Warren Wilson College in Asheville, NC in 2004 and his MS in Environmental Science from the University of Tennessee at Chattanooga in 2007.  He joined Dr. Buchwalter’s lab in fall 2008 as a Ph.D. student in Environmental Toxicology.  His previous work focused on the detection of pharmaceuticals in the Tennessee River and potential impacts on secondary productivity.  His current work focuses on the identification of stressors to aquatic insects in streams impacted by mountaintop removal – valley fill coal mining.  Further, will be investigating the biodynamics and toxicological effects of dissolved and dietary selenium on aquatic insects.
Conley Publications

Sarah Wickman
Sarah obtained her BS in Biology from the University of Northern Iowa in Cedar Falls, IA in 2003.  She joined Dr. Buchwalter’s lab in fall 2009 as a Ph.D. student in Environmental Toxicology.  She was previously involved in research investigating signal transduction of oncogenic pathways and small molecule inhibitors of preclinical glioma models. Her current work is part of an NSF-funded project focused on comparative ion trafficking in stream insects. Sarah’s work will characterize dissolved fluxes (influx and efflux) of Ca, Cd and Zn in hydropsychid caddisflies and ephemerellid mayflies. This work will be examined in an evolutionary context, and employ phylogenetically based statistical tools to examine the extent to which phylogeny can inform physiological processes.  Wickman Publications

 

 

Lab Emeriti

Caitrin Martin, MS
Caitrin finished her MS in July, 2007, focused on dietary Cd accumulation in predatory stoneflies (see her 2007 ES&T paper in the publications section). She is now a Peace Corps Volunteer in Senegal , West Africa.

Daniel Lambert
Daniel worked with us for several months as an undergraduate, and contributed to our work in metal trophic transfer studies and digestive processes. He is now enrolled in the College of Veterinary Medicine at NCSU.

Jen Flippin
After completing her MS in Toxicology at NCSU, Jen worked with us on studies of Hg bioaccumulation and oxidative responses.

Esther Seisay Adam-Samura
Esther worked with us as an undergraduate for two years.  She ran respirometry experiments and assisted with other projects.

 

Book Chapters:

    Buchwalter, D.B. 2008. Metals. In: Introduction to Biochemical Toxicology. 4th Edition. Edited by: E. Hodgson and R.C. Smart. John Wiley and Sons. New York.

    Resh, V.H., D.B. Buchwalter, G.A. Lamberti and C.H. Eriksen, 2007. Aquatic Insect Respiration. In: An Introduction to the Aquatic Insects of North America . 4 th Edition. Edited by: R.W. Merritt, K.W. Cummins and M.B. Berg. Kendall/Hunt. Dubuque, Iowa.


Peer Reviewed Publications:

2009

  1. Conley, J.M., D.H. Funk and D.B. Buchwalter. 2009. Selenium bioaccumulation and maternal transfer in the mayfly /Centroptilum triangulifer/ in a life-cycle, periphyton-biofilm trophic assay. /Environ. Sci. Technol. /43:7952-7957.
  1. Xie, L. D.H. Funk and D.B. Buchwalter. 2009. Trophic transfer of Cd from natural periphyton biofilms to the grazing mayfly /Centroptilum triangulifer/ in a life cycle test. /Environmental Pollution/. E-Pub ahead of print.
  1. Xie, L., J.L. Flippin, N. Deighton, D.H. Funk, D.A. Dickey and D.B. Buchwalter. 2009. Mercury (II) bioaccumulation and antioxidant physiology in four aquatic insects. Environ. Sci. Technol. 43:934-940.

2008

  1. Buchwalter, D.B., S.N. Luoma. C.A. Martin, D.J. Cain, L., Xie, L. and Garland, Jr. T. 2008.  Aquatic insect ecophysiological traits reveal phylogenetically based differences in dissolved cadmium susceptibility. Proc. Nat. Acad. Sci. 105:8321-8326.
  1. Buchwalter, D. B., Daniel J. Cain, William H. Clements, and Samuel N. Luoma. 2008. Correction to: Using Biodynamic Models to Reconcile Differences between Laboratory Toxicity Tests and Field Biomonitoring with Aquatic Insects. Environ. Sci. Technol. 42: 3117.
  1. Cope, W.G., R.B. Bringolf, D.B. Buchwalter, T.J. Newton, C.G. Ingersoll, N. Wang, T. Augspurger, F.J. Dwyer, M.C. Barnhardt, R.J. Neves, and E. Hammer. 2008. Differential exposure, duration, and sensitivity of Unionoidean bivalve life stages to environmental contaminants. J. N. Am. Benthol. Soc. 27:451-462.
  1. Xie, L, D. Lambert , C.A. Martin,D.J. Cain, S.N. Luoma and D.B. Buchwalter. 2008. Cadmium biodynamics in the oligochaete Lumbriculus variegatus and its implications for trophic transfer. Aquat. Tox. 86:265-271

2005-2007

  1. Martin , C.A. , D. J. Cain, S.N. Luoma and D.B. Buchwalter. 2007. Cadmium Ecophysiology in Seven Stonefly (Plecoptera) Species: Delineating Sources and Estimating Susceptibility. Environ. Sci. Technol. 41:7171-7177.
  1. Buchwalter, D. B., Cain, D.J., W.H. Clements and S.N. Luoma. 2007.Using Biodynamic Models to Reconcile Differences Between Laboratory Toxicity Tests and Field Biomonitoring with Aquatic Insects. Environ. Sci. Technol. 41:4821-4828.
  1. Cain, D.J., D.B. Buchwalter and S.N. Luoma. 2006. The influence of metal exposure history on the bioaccumulation and subcellular distribution of aqueous cadmium in the insect Hydropsyche californica. Environ. Toxicol. Chem. , Vol. 25 (4):1042-1049.
  1. Buchwalter, D.B. and S.N. Luoma. 2005. Differences in dissolved Cd and Zinc uptake among species of stream insects: Mechanistic explanations. Environ. Sci. Technol. 39: 498-504.

2002-2004

  1. Buchwalter, D.B., J.F. Sandahl, J.J. Jenkins, and L.R. Curtis. 2004. Roles of uptake, biotransformation, and target site sensitivity in determining the differential toxicity of chlorpyrifos to 2 nd - 4 th instar Chironomus riparius . Aquat. Tox. Vol. 66(2): 149-157.
  1. Buchwalter, D.B., J.J. Jenkins, and L.R. Curtis. 2003. Temperature influences on water permeability and chlorpyrifos uptake in aquatic insects with differing respiratory strategies. Environ. Toxicol. Chem. Vol. 22(11): 2806-2812.
  1. Buchwalter, D.B., J.J. Jenkins, and L.R. Curtis. 2002. Respiratory strategy is a major determinant of [ 3 H]-H 2 O and [ 14 C]-chlorpyrifos accumulation in aquatic insects. Can. J. Fish. Aquat. Sci. 59:1315-1322.

1994-1998

  1. Fort D.J., Stover E.L., Bantle J.A., Rayburn J.R., Hull M.A., Finch R.A., Burton D.T., Turley S.D. , Dawson D.A., Linder G., Buchwalter D., Dumont J.N., Kumsher-King M., Gaudet-Hull A.M. 1998. Phase III interlaboratory study of FETAX, Part 2: Interlaboratory validation of an exogenous metabolic activation system for frog embryo teratogenesis assay--Xenopus (FETAX). Drug Chem. Toxicol. Vol. 21(1):1-14.
  1. Buchwalter, D.B., G. Linder, and L.R. Curtis. 1996. Modulation of cupric ion activity by pH and fulvic acid as determinants of toxicity in Xenopus laevis embryos and larvae. Environ. Toxicol. Chem. , Vol. 15(4): 568-573.
  1. Bantle, J.A., D.T. Burton, D.A. Dawson, J.N. Dumont, R.A. Finch, D.J. Fort, G. Linder, J.R. Rayburn, D.B. Buchwalter, M.A. Maurice, and S.D. Turley. 1994. Initial Interlaboratory Validation Study of FETAX: Phase I Testing . J. App. Tox. Vol 14(3): 213-223.
  1. Bantle, J.A., D.T. Burton, D.A. Dawson, J.N. Dumont, R.A. Finch, D.J. Fort, G. Linder, D.B. Buchwalter, J.R. Rayburn, and S.D. Turley. 1994. FETAX Interlaboratory Validation Study: Phase II testing. Environ. Toxicol. Chem. , Vol.13(10): 1629-1637.

Other Articles:

    Buchwalter, D.B., L. Xie and Y. Arai 2009. Assessing Mercury Contamination and Bioavailability in Great Smoky Mountains National Park Aquatic Habitats. Final report to Great Smokey Mountains Conservation Society.

    Buchwalter, D.B., and D.J. Cain. 2005. Species-specific responses to environmental contaminants: A case for comparative physiology. SETAC Globe 6(3). 31-32.

    Buchwalter, D.B, Jenkins, J.J., Judd, D.D., and Curtis, L.R. 2001. Testing toxicological hypotheses based on ecological observations: A case study using aquatic insects and epithelia. SETAC Globe 2(1).

    Jenkins, J.J. and D. Buchwalter. 1998. Pesticides: Human and Environmental Health. In: Nutrient and Pest Management Considerations in a Resource Management System Plan. National Employee Development Center , USDA Natural Resources Conservation Service.