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Dr. Robyn Hannigan - Environmental Scientist
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Did you know that fish have growth rings, just like trees? Tree rings are easy to count, as they are just part of the trunk, growing outward. But can you guess where to find growth rings in a fish? They’re in a surprising place—the ear bones, which are called otoliths. These help fish balance and let them know which way is up. They can be incredibly small or pretty big…anywhere from one-tenth of an inch to a full inch.

In my Water-Rock-Life (WRL) research lab at Arkansas State University, my students and I are studying the ear bone chemistry of fish from local rivers. Besides age and growth rates, we can look at the chemistry of the rings on the ear bones to find out their migration patterns, preferred habitat, and exposure to chemical pollution.

Our work is important to people who manage fish populations because we can find out about reproduction and survival rates of fish. The U. S. fishing industry is a 50 billion dollar a year industry.  Also, Native communities rely on fishing for food and for maintaining their cultural history. More and more fish species are disappearing because of over fishing or poor management because people don’t know where the fish are reproducing or how many fish that are stocked in a river actually survive to adulthood. Using the otoliths, we can provide fisheries managers with important information that can help set guidelines for minimum size and catch limits. This way, we protect species by protecting the areas that are used for breeding and give young fish enough time to mature and reproduce.

All of my research is about using a technique called mass spectrometry to identify and measure unknown quantities of chemicals in all kinds of samples from fish ear bones to human hair. First we take a sample, and using a mass spectrometer, break it apart with heat or light energy into its smallest bits, which are called ions. Each ion has a mass that identifies it, sort of like a fingerprint. Using the masses of the ions we make, we know what is in a sample.  To find trace amounts of elements in otoliths, I measure the mass of individual ions by zapping the ear bone with a laser, making ions of individual atoms and counting the abundance of those ions.

Just as I go through a complex process to discover the makeup of different chemicals present in the otoliths, I went through a complicated process of self-discovery on my way to becoming an environmental geochemist. I had a rough start in school because although I loved making up science experiments at home, I wasn’t a very good student. Growing up poor, I felt the pressure of low expectations all around me. I thought studying science meant boring classes, and it took me a long time to realize that it could be fun and exciting like it was at home.

My professors at the State University of New York at Buffalo and the University of Rochester believed in me enough to give me a leg up when I needed it and to push me beyond my own expectations. I got a late start, but once I found out I was good at something, I pursued it wholeheartedly.

My experience led me to create the Research Internships in Science of the Environment (RISE) summer program. Each year underrepresented minority college students come from across the country to create their own projects in a professional lab. Here they can discover their capabilities as future scientists. And from the diverse insight that they bring, I’ve expanded my own research. Just as in life, diversity is key to the growth of science.

Remember that it’s okay to learn at your own pace. Thanks to mentors who saw my potential, I went beyond even my own expectations. If you find what you like, connect with people who will give you the opportunity to explore to the fullest. Never lose your enthusiasm for science.


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