How a Lemon Shark Inspired a Career in Aquatic Toxicology or What I Am Doing with My Life.

”I had dreamed of becoming a scientist in general, and a paleontologist in particular, ever since the Tyrannosaurus skeleton awed and scared me at New York’s Museum of Natural History when I was 5 years old.”
– Stephen Jay Gould, Rocks of Ages: Science and Religion in the Fullness of Life (1999)

My own Tyrannosaur was a lemon shark (Negaprion brevirostris) at the Cincinnati Zoo when I was about that same age.  The powerful presence of this living creature held forth here for my kindergarten-self to observe seared itself into my brain, locking in those neurons which would direct me to a biological life.   I know this fact to be true because my Mom recently unearthed a drawing I did from the first day of kindergarten, which of course was of a fish.  And while my drawing skills haven’t improved markedly, my love of fish and intellectual curiosity grew exponentially.  That intellectual T. rex, struck again when I was twenty only in the form of an orangethroat darter (Etheostoma spectabile), held gently in my hands while kneeling in a creek, still cold with spring rains.  That beautiful little fish, shimmering orange, green, and blue in the April sun, showed me the steps to the path that would lead me to becoming a biologist.  What I later realized was that for others to have that same transformative moment, those fish and the water where they live must be protected.  So my career path transitioned from enthusiastic student, to biologist, to ichthyologist, to environmental researcher.lemon shark orangethroat darter

fish art at fiveMy undergraduate life saw my introduction to molecular ichthyology, looking at genetic differences between behaviorally divergent salmon populations.  My Master’s work focused on using molecular techniques to identify changes in population genetics associated with differences in metal concentrations, particularly those associate with anthropogenic impacts in pristine environments. Later, working with a US EPA contractor, I was able to use my skills as an ichthyologist and an environmental scientist through the course of many field and laboratory projects.  My doctoral work focused on understanding and prioritizing the risk/hazard of environmental contaminants.  As I moved into my NRC Associateship, I felt confident that I would be able to utilize all those hard acquired skills in challenging and cutting edge research being done at the US EPA Midcontinent Ecology Division Laboratory.

As an NRC Associate, I work with a team of talented scientists at the US EPA to develop novel and innovative approaches to environmental assessment and monitoring for chemical toxicity.  The EPA Mid-Continent Ecology Division (MED), where I hold my appointment, has long been known as source for high quality environmental science and aquatic toxicology, and is in large part responsible for many of the standard monitoring and assessment methods within the Agency, nationally, and internationally.  This history of high quality research resulting in improved environmental practice was one of the primary reasons I applied for my fellowship at this lab.  The other reason was the opportunity to work with the EPA scientists, many of whom are considered global experts within the field of aquatic toxicology.  Most of my research focuses on chemicals of emerging concern (CECs).  This category, CECs, is a catch-all for a wide swath of compounds with limited (often non-existent) regulatory criteria and rudimentary (if any) aquatic toxicological profiles.  While continually improving analytical techniques can detect these chemicals in aquatic systems, little in known about their potential effects on organisms. My research focuses on two areas: prioritizing CECs based on available data, and applying molecular and omics approaches to field studies. Working with two world class scientists as mentors, Dr. Gerald Ankley and Dr. Daniel Villeneuve, as well as a support team of extraordinary scientists, I have been able to work on a number of different projects which are expected to advance the field.

Much of my work has focused on the development and refinement of effects-based aquatic testing and monitoring.  Effects-based monitoring thus far has been focused on short-term whole animal toxicity endpoints.  While these data are incredibly powerful, the power is retrospective, identifying problems only after they have reached the point of causing adverse effects.  As identified in National Research Council’s “Toxicity Testing in the 21st Century” testing (and monitoring) strategies need to move away from whole organism testing towards more molecular and in vitro evaluations.  The approach to accomplishing this and the focus of much of my research is the utilization of the “adverse outcome pathway” (AOP).  This approach recognizes that pathways are involved, initiated by a chain of events starting with an exposure and leading along increasing levels of biological organization until it reaches impacts on the population level.  The adverse outcome pathway approach, defined and championed by the EPA researchers at MED, provides a framework that links this response pathway to events that are important to established regulatory endpoints (e.g., mortality, development, reproduction and extirpation).  In the lab, much work has been done to establish key chemical and biological events and links between these levels of biological organization; the focus, and primary challenge of my research, is to transition these concepts to the field.  In the field, this AOP-focused effects-based monitoring provides a means to evaluate complex environments with multiple stressors in a way that is not possible through traditional chemical-based assessment.  Our research efforts are focused on using caged fathead minnows (Pimephales promelas; the white rat of aquatic ecotoxicology) as a means to monitor biological response to the environment.  While this is still a whole organism in-vivo test, by evaluating multiple endpoints from within each single fish, overall we are able to increase the volume of information gathered, while decreasing the overall number of fish used per evaluation.  Fish are exposed in the field for anywhere between 6 hours and 15 days, depending on the study.  The fish are necropsied and multiple tissues are collected, including liver, gonad, blood/plasma, brains/pituitary, thyroid enriched tissue, gills, and brains (we also save the remaining tissue for chemical analysis.  My favorite analogy for this process is that the fish are “parted out like a stolen Camaro”.  Multiple assays are done including transcriptomics, metabolomics, targeted qPCR, measurements of steroid hormones and vitellogenin (a key biomarker for exposure to endocrine active compounds).  Aside from the development of the field studies, one of my primary duties has been to assimilate this plethora of data into information that is useful to scientists and eventually regulators.  This has taken the form of presentations at national meetings (Society of Environmental Toxicology and Chemistry) and several manuscripts, the first of which was just accepting into Environmental Science and Technology.caged fathead

The other major project I am involved with focuses on the prioritization of CECs for evaluation.  One of the major groups of CECs are pharmaceuticals, which we now know are found in virtually every municipal effluent.  The concern with human and veterinary drugs is that they are biologically active, engineered to cause a specific biological effect in a target organism.  While typically targeted at humans or other mammals, given the overall conservation of the critical targets, there is great potential for effects in non-target organisms, particularly aquatic species, like fish and macroinvertebrates.  Of the 5000 or so active pharmaceutical ingredients, only a handful have been evaluated for chronic (non-lethal) effects in aquatic organisms, and even those tested have not been evaluated for their specific biological consequences of the drug action.  The research we are doing here at MED focuses on a multi-faceted approach to prioritization.  There are several key elements to our approach, including: evaluation of protein sequence similarity (to identify the likelihood of response in non-target organisms), identification of molecular modes of action (MOA), and mining the vast repositories of pharmacological development data.  The focus of my work is to develop a read-across, from mammals (where there is an enormous data set of pharmacokinetic/dynamic information), to fish (and other aquatic organisms), where little data exists.  By mining the mammalian literature and databases I have developed an extensive, fully referenced database.  It currently contains information for 1400 drugs and 120 therapeutic classes, and includes physical properties, pharmacokinetics, toxicity and therapeutic dose parameters.  The database forms the core of a computer application that utilizes probabilistic distributions to prioritize pharmaceuticals.  These prioritizations can take the form of individual parameters or multi-parameter assessment, and in use of the probabilistic approach given the program the ability to assess both drugs in the database and those not yet included, or even unknown.  My work will be incorporated into a larger overall framework which includes specific information about the adverse outcomes based on MOA and the molecular target similarity.  In our research here at MED we have utilized the database and program in a number of different ways.  As part of our developing monitoring and assessment program for CECs, I used the program to identify a prioritized list of drugs for inclusion into our analytical chemistry evaluation.  We have also used it to identify compounds for study for several MOA specific analyses.  Further we are currently using it to develop a list of target compounds for the assessment of the mammal to fish read-across approach, specifically understanding how mammalian pharmacokinetic responses might translate in fish.

My time at the EPA in Duluth, MN has provided me an opportunity to hone my skills and develop as a scientist.  I have been afforded the opportunity to develop some unique and challenging projects.  I am also allowed an inside look at the development of environmental monitoring and assessment directed at policy and methods.  The tests and approaches, codified into regulatory endpoints, provide a repeatable and simplified way to assess the environment, but they did not all start that way.  They start with an idea: “how things can be done better?” “How can we better protect the environment?” that progresses into testing, application and analysis of the results, and re-evaluation, in an iterative process to identify approaches that work and fix or discard those that do not.  All along the way important considerations, like reducing the number of organisms or moving towards more in vitro assays, are incorporated into the framework.  Working with the world class researchers here has challenged me to become a better writer, presenter, investigator, and overall a better scientist.

As a scientist, I am always looking for my next “T-rex” moment, that moment of terrified astonishment, that spike of intellectual adrenaline that will drive my curiosity and creativity into the next evolution of my career.  Along the way I also hope that I can inspire that moment in those around me through mentoring, teaching, or just inspired collaboration with fellow scientists.  Moving into my third year of my post-doc and looking to the future, and what that next step will be, I know that no matter where that it is, my time at the EPA-MED lab will have served me well.



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One Response to How a Lemon Shark Inspired a Career in Aquatic Toxicology or What I Am Doing with My Life.

  1. Pingback: I am a Fish Nerd/the Amazon Rainforest is awesome | Jason's Ramble

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