Welcome to the Rhubarb talks website
The 'Rhubarb Talks' are a series of seminars by PhD students for PhD students at NOCS.
Upcoming seminars are posted below and cover a whole range of scientific exploits. Talks are held every other Monday afternoon at 4.30pm in the postgrad lounge (node 086) and are accompanied by nibbles and refreshments.
For more info or to volunteer for a talk, please contact The Rhubarb Team: Liz (E.Sargent@noc.soton.ac.uk), Rosanna (R.Greenop@noc.soton.ac.uk), Maike (mjsp106@soton.ac.uk) or Sara (Sara.Cregeen@noc.soton.ac.uk)
Tuesday 3rd of April Liz Sargent will present: Assessing the direct contribution of
TRICHODESMIUM TO export
Trichodesmium, a colonial marine
cyanobacterium,
is integrally involved in ocean biogeochemical cycling as it is a
significant supplier of fixed nitrogen to the warm surface ocean.
Recent reports have
suggested that Trichodesmium is also important in the subsurface layer, and actively fixes nitrogen in the deep chlorophyll maximum (DCM); however, the role
Trichodesmium plays in the biogeochemistry of deeper waters has yet to be described. This study focuses on
Trichodesmium’s involvement in the direct export process.
Contrary to previous expectations, results suggest that despite its
buoyancy this organism is a constituent of sinking material. Sampling on
research cruises in the eastern subtropical and tropical
Atlantic, and in the Gulf of Mexico showed Trichodesmium was
commonly present below 100 m in three forms: tufted colonies, free
filaments, and free filaments included in aggregations with other
organisms/faecal matter. The Marine Snow Catcher (MSC),
a 100 L messenger-operated PVC closing water bottle, and
in situ Stand Alone Pumping Systems (SAPS) were used to collect
sinking particles, which were imaged and preserved for post-cruise
assessment. All sub-DCM MSC collections between 80-250 m in areas where
Trichodesmium was a significant counterpart of the surface population included negatively buoyant colonies sinking at 12 - 120 m d-1, as well as free filaments; SAPS collections also revealed the presence of free filaments in low concentrations
as deep as 500 m. Further microscopic analysis of these colonies will allow for the elucidation of the mechanism of sinking in
Trichodesmium, such as gas vacuole collapse, as well as aiding in describing its involvement in the export flux of POC and PON.
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