Dr. Jason P. Turner
Department of Marine Science
University of Hawaii at Hilo
200 W. Kawili St.
Hilo, HI 96720
Ph.D. Texas A&M University (2004)
M.S. Texas A&M University (1998)
B. A. Texas A&M University at Galveston (1994)
Foodweb ecology of estuarine and marine systems primarily focusing upon upper trophic levels and higher vertebrates (fishes, sea turtles, marine mammals). Presently utilizing analytical approaches to retrospectively determine dietary preferences using fatty acids (PUFAs) and stable isotopes (δ13C & δ15N).
I have been involved with marine biological research for the past 10 years and have conducted projects spanning several different habitats, techniques and taxonomic groups. Research projects have included the use of morphometrics, physiology, tracking studies, fisheries research, and ecosystem dynamics. I have worked with all levels of organism within the aquatic environment including plankton, invertebrates, fishes, sea turtles, and marine mammals. Essentially I am a marine ecologist with a special interest in food web dynamics and novel dietary tracers. I have used a suite of biomarkers to answer questions relating to the movement of individuals and organic nutrient resources through aquatic ecosystems.
My current research involves the use of biomarkers (fatty acids and stable isotopes) as tracers to retrospectively determine dietary histories of fishes and invertebrates and sources of organic matter in estuarine and marine systems. My approach relies on utilization of classic carbon and nitrogen stable isotope (δ13C & δ15N) analysis as well as analyses using polyunsaturated fatty acids or PUFAs. While most ecologists are familiar with the application of C and N stable isotopes as food web tracers, the use of fatty acids for this purpose has only recently been applied to studies of aquatic food webs. There are three important distinctions when using stable isotopes and fatty acids as tracers. First, C and N are conservative tracers and fatty acids are not strictly conservative. Second, fatty acids provide a much richer milieu of information from which energy (and especially lipid) flow can be inferred. Finally, specific polyunsaturated (multiple, double-bonded) fatty acids are essential for proper growth, development, survival, fecundity, and hatchability in many aquatic fishes and invertebrates and therefore can reflect the quality of nutrient resources in specific microhabitats.
Recently I have used fatty acid composition to describe the energetic basis for small crustacean and juvenile fish production in Sargassum mat ecosystems in the Gulf of Mexico, suggesting that phytoplankton is the major source of organic matter entering this food web, not Sargassum, the largest supply of biomass in the system. This analysis was possible because the fatty acid profiles of Sargassum, green algae (which grow as periphyton on the Sargassum), and phytoplankton differ dramatically. Under normal circumstances between 10-20 different fatty acids can be used as tracers of energy and lipid flow. These fatty acids can range from saturated fatty acids which primarily serve as energy stores to long-chain PUFAs which serve critical physiological roles as precursors of reproductive and growth hormones, regulators of cell membrane fluidity, and perhaps even as determinants of dietary food quality. Further, I have used both stable isotope and fatty acid tracer approaches to backtrack the ecosystem energy flow networks in commercially, recreationally, and ecologically important fishery species in coastal Louisiana. Specifically, we collected samples across a gradient of known lake productivity (spanning oligotrophic to eutrophic) and lake morphology from very shallow (and likely benthic dominated) to very deep (and likely pelagic dominated) systems. The biggest challenges with using fatty acids as energy flow tracers are due to the fact that they are not entirely conservative, and that a tremendous amount of information will be obtained from all of the different fatty acids assessed. I currently use trophic mixing models to untangle this flow network. Trophic position of ecosystem components are determined using carbon and nitrogen stable isotopes while feeding linkages are determined using fatty acids and stomach contents. Energy budgets for each nursery habitat for the entire study area are then calculated using models in order to balance energy flow in and out of each trophic group.
I am currently exploring projects which will utilize these techniques to answer specific questions relating to the flora and fauna of the Big Island of Hawaii. See "Research" for the latest descriptions.