Effects of nitrogen sources and plankton food-web dynamics on habitat quality for the larvae of Atlantic bluefin tuna in the Gulf of Mexico

OneNOAA Science Seminar Series

Title: Effects of nitrogen sources and plankton food-web dynamics on habitat quality for the larvae of Atlantic bluefin tuna in the Gulf of Mexico
Seminar No. 6 of 13 in NOAA's RESTORE Science Program Seminar Series: Actionable Science in the Gulf of Mexico

Speaker: Dr. Michael Stukel, Associate Professor, Florida State University

Sponsor: NOAA RESTORE Science Program and NOAA's National Ocean Service Science Seminar Series. Points of contact: Andrew.Lade@noaa.gov and for webinar questions, Tracy.GIll@noaa.gov

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Abstract: Bluefin tuna spawn in some of the most oligotrophic regions of the Gulf of Mexico. In these stratified, low nutrient waters, low abundances of their mesozooplankton prey can lead to high starvation rates among Bluefin larvae and commensurately decreased recruitment. Larval prey availability may become an even greater concern for this species in a future ocean in which warmer temperatures simultaneously drive decreased ecosystem productivity through increased stratification and increased food requirements as a result of higher metabolism. To investigate linkages between physical circulation, the lower trophic level food web, and larval Bluefin, we have pursued two complementary modeling approaches: three-dimensional coupled ecosystem modeling and mass-balanced constrained food web modeling. In the first approach, we have developed a three-dimensional ecosystem model from nutrients to large and predatory mesozooplankton, and validated the model against SEAMAP zooplankton abundance measurements and in situ zooplankton rate measurements. We then developed a Lagrangian larval tuna model to advect simulated larvae through the dynamic prey field to quantify growth, starvation, predation, and survivorship. We use this model to investigate processes promoting larval tuna survivorship in current and future climate conditions. With our second approach, we explicitly acknowledge that larval tuna are selective feeders on specific mesozooplankton taxa and hence have constructed a mass-balance constrained food-web model that includes much greater complexity within the zooplankton community. This food-web model is constrained using extensive (nutrients to tuna) measurements made during Lagrangian experiments conducted on two focused cruises in the Gulf of Mexico. This modeling approach allows us to trace nitrogen from upwelled nitrate and nitrogen fixation through zooplankton communities and into larval tuna. We then show how these modeling approaches can be linked to mechanistically predict the impact of interannual and longer-scale changes in the Gulf of Mexico on larval tuna recruitment.

Bio: Dr. Michael Stukel is an associate professor at Florida State University. His research spans the intersection of plankton ecology and marine biogeochemistry. He has a love for all the zooplankton of the oceans and a passion for understanding how these microscopic organisms influence everything from the global climate to local fisheries yield. Appendicularians are his favorite plankton. Unless it's ctenophores. Or salps. Perhaps phaeodarians, krill, Lingulodinium polyedrum, hyperiid amphipods, Tomopteris, or pyrosomes. It might be copepods. But he doesn't like chaetognaths. They always get stuck on the filter.

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(Michael Stukel, PhD, Associate Professor, Florida State University)