CC&E Spring 2017 Seminar Series – A Surprising Role for Picocyanobacteria in the Opean-Ocean Silicon Cycle

This Friday, January 20, 2017 the College of the Coast & Environment will be hosting Dr. Jeff Krause from the Dauphin Island Sea Lab in Alabama and Assistant Professor, University of South Alabama in Mobile, Alabama. Dr. Krause’s topic for the seminar will be “A surprising role for picocyanobacteria in the open-ocean Silicon cycle.” Please join us in the Dalton J. Woods Auditorium for this very informative talk.


Surprisingly, picocyanobacteria from the genus Synechococcus were observed to accumulate elemental Silicon. Despite the low absolute quantities (amoles Si cell-1), the ratio of Si to organic-matter was nearly 50% of that for diatoms in the eastern equatorial Pacific. Initial comparison of Si standing stocks suggested that the contribution of Synechococcus to Si, at times, exceeded that for living diatoms in this region due to disparity in their relative abundances. Here I report factors regulating Si accumulation in Synechococcus in the laboratory and their contribution to total biogenic silica production in the North Atlantic subtropical gyre. While many clear patterns emerge in the culture data set, e.g. variability in Si quota as a function of silicic acid concentration, the purpose of Si accumulation in Synechococcus remains a mystery. During field work in the North Atlantic subtropical gyre, the picoplankton size class was observed to contribute a measurable, and at times significant, proportion of biogenic silica standing stock and to its rate of production. Our results suggest picoplankton may have a small, but relatively stable, contribution to biogenic silica in this region, which underlies a more dynamic microplankton biogenic silica pool driven by diatoms. If the Si form associated with cells is hydrated amorphous silica, this may provide picocyanobacteria cells or aggregates of dead cells with ballast, potentially increasing export efficiency in the open ocean. Regardless of the ballast effect, our understanding of the factors controlling regional biogenic silica production and our interpretations of particulate matter elemental ratios (e.g. Si:C) in the mid-ocean gyres both require revision.

Lunch will be provided immediately following the seminar in the conference room next to the auditorium.

Time: 11:30 a.m. – 12:15 p.m.
Where: Dalton J. Woods Auditorium
LSU Energy, Coast, and Environment Building