David Goodwin, Ph.D.

RESEARCH INTERESTS

My research involves documenting and interpreting records of environmental variation archived in the hard parts of modern and fossil organisms. This is accomplished primarily through calibration of environmental conditions with skeletal archives: specifically, geochemical variations and patterns of shell growth. The geochemical component of my work focuses largely on stable isotopes and trace elements, while the analysis of growth patterns focuses on periodic increments deposited in response to biological and environmental stimuli as well as astronomical pacemakers. Together, these analytical techniques, commonly referred to as sclerochronology, have facilitated work in several different research areas. While each has a different focus, they are connected by a common theme: how are environmental conditions recorded in the geologic record in general, and in the skeletons of organisms in particular? And, how can these archives be used to address a variety of biological and geological questions? My current research focuses on three areas of primary interest: 

• understanding records of environmental variation recorded in the shells of bivalve mollusks, how these archives are influenced by the biology of the animal, and how to design sampling and analytical techniques that maximize the utility of sclerochronologic archives;
• using sclerochronological archives to address ecological and paleoecological questions, particularly those related to the growth and geographic distribution of modern and fossil organisms, and to understand the environmental factors that control these variables—especially in times of rapid climate change; and,
• documenting and interpreting the fossil record of bivalve evolution through investigation of ontogenetic patterns of shell growth within a phylogenetic context.

The common thread that runs through each of these areas is the idea that organisms with accretionary skeletons are essentially biological chart recorders: their shells (teeth, bones, etc.) contain records of the environmental conditions experienced during growth. 

STUDENT RESEARCH OPPORTUNITIES

Collaborating with students on research projects is one of the best parts of my job. It's a win-win situation. You help develop new ideas that contribute to the geological/biological understanding of our world, learn how to do research and get invaluable experience that will help get into graduate school or land a job after college. I get the privilege of working one-on-one with enthusiastic, motivated students and their fresh ideas.

I keep an “ideas" file in my desk. It contains a list of potential small research projects. You can peruse the file to find projects that interest you or use these suggestions to help formulate your own questions. In return, I ask that upon completion of your own project you add a idea to file. In this way, you will inspire new students and myself to move in new research directions.

Projects will include development of a scientifically significant hypothesis, grant writing (if necessary) to cover field and analytical expenses (don't worry—writing proposals is easier that you might think), field and lab work, and preparation and presentation of your work.

HOW TO BUILD A MICROMILL

The micromill has become one of the most important tools used in sclerochronological research today.  And while there are excellent "out-of-the-box" options available, most notably the New Wave Micromill and the Carpenter Microsystems microsampler, these systems are expensive, can be difficult to maintain, and most importantly, are essentially "black boxes" to the end user. Accordingly, I hope my simple, inexpensive, and straightforward design will be useful to those interested in adding micromilling capabilities to their own labs.

Before I go any further, a note on my motives...I am not interested in profiting from this design, nor am I affiliated with any of the companies that manufactured the components I have used. I think of this project as an open-source micromill design. The basic design for this micromill is based on the original Dettman-Lohmann micromill (Dettman, D.L., and Lohmann, K.C., 1995, Microsampling carbonates for stable isotope and minor element analysis; physical separation of samples on a 20 micrometer scale. Journal of Sedimentary Research, 65,3a: 566-569). If you have comments, questions or concerns, please feel free to contact me.

Please keep in mind this site is a work in progress. This is the second micromill system I have designed and constructed. I will continue to update this site as I make progress. 

First things first…

• Computer-controlled micro motion-control is cool!
• When doing scientific research, black boxes should be avoided at all costs!
• There is nothing like the satisfaction that comes from designing and building something yourself.

So what does a mincromill do? The video below show a micromill drilling a single sample from a cross-section of a bivalve mollusk shell. The video was shot using a Sony Cyber-Shot 8.1 compact camera. The camera was mounted on a tripod and positioned looking down one of the oculars of a binocular microscope. This is exactly what you would see if you were looking through the microscope at the micromill.

SCLEROCHRONOLOGY LISTSERV

The Sclerochronology Listserv is a discussion list for all those interested in the field of sclerochronology.  The listserv exists to promote electronic communication among sclerochronologists. While intended primarily for professionals and students, the sclerochronology listserve welcomes participation and input for all those interested in the field. I maintain the Sclerochronology Listserv here at Denison.

ISOGEOCHEM

Isogeochem is an e-mail discussion list and reference web site for stable isotope geochemistry. The objective of the discussion list is to promote the exchange of news and information among those with an interest in stable isotope geochemistry, to provide new contacts within the stable isotope community, and to enhance collaborative efforts among researchers from varying disciplines. The list is intended not only as a discussion forum for isotope geochemists, but also as a source of information and help for researchers from other fields interested in applying stable isotopes as a tool in their own studies. (Text taken from the Isogeochem web site.)

MOLLUSK GROWTH FUNCTION GENERATOR

The Mollusk Growth Function Generator (AKA: MoGroFunGen) is a novel mathematical method that relates shell growth and time using oxygen isotope variation to reconstruct intra-annual growth rates in bivalve mollusks.