FSU Plankton Ecology and

Biogeochemistry Lab


The Costa Rica Dome (CRD) is an open ocean upwelling system in the Eastern Tropical Pacific that, for reasons that are still poorly understood, experiences incredibly strong blooms of the cyanobacteria Synechococcus. In July 2010, I was part of a team of biological oceanographers and marine chemists who participated in a cruise to understand the ecology and biogeochemistry of this unique region, which overlies one of the largest hypoxic zones in the ocean.


My role in the project was to determine the connection between the plankton community and carbon export, while also measuring the magnitude of vertical carbon and nitrogen fluxes out of the surface ocean. In service of the latter objective, I used sediment traps and 234Th:238U disequilibrium measurements to track carbon fluxes out of the euphotic zone and remineralization patterns with depth. To address the first question, I used phycoerythrin (PE) as a pigment tracer to track Synechococcus through the ecosystem. In particular, I measured mesozooplankton gut PE contents and sediment trap PE contents, and also compared the data with protozoan grazing measurements on Synechococcus made by my collaborators. The results showed that while Synechococcus is preyed upon by mesozooplankton to some extent (likely when mesozooplankton are feeding on aggregates), very little Synechococcus arrives undigested into the sediment trap. Most Synechococcus production that was exported to depth was mediated by protozoan trophic transfers, though even this pathway represented only a small proportion of total carbon flux.


In addition to the aforementioned trophic transfer study, I am preparing a manuscript to address the biogeochemistry of the CRD. Preliminary results suggest that despite the productivity of the region, very little carbon is exported out of the base of the euphotic zone (e-ratio ~ 0.05%), because of high remineralization rates beneath the mixed layer. Results also show that nitrate uptake was significantly higher than gravitational fluxes of particulate nitrogen, and suggest preferential remineralization of phosphorus relative to nitrogen and carbon.




This portion of our website is specifically designed to showcase our research for other oceanographers.  If you would like a broader overview of our work that was designed to be more accessible to the general public, please click on the 'Outreach' link on the top right.


Contact: Mike Stukel (mstukel@fsu.edu)

Florida State University

Dept. of Earth, Ocean, and Atmospheric Science

Center for Ocean-Atmospheric Prediction Studies