• Speaker: Dra. María L. Calleja. Max Planck Institute







Esporles, November 25, 2019.


The export of surface ocean dissolved organic carbon (DOC) excess to deeper layers through convective mixing is a well-recognized seasonal passive transport of carbon into the ocean interior.


The semi-labile fraction of subducted DOC provides a substrate to heterotrophic prokaryotes (HP) inhabiting the upper mesopelagic layer and leads to remineralization processes and oxygen consumption.


Together with this mechanism active transport by vertically migrating animals, that feed in the surface at night and retreat in mesopelagic waters during the day, represents an important, albeit not quantified, daily supply of DOC from the surface to deep waters, with consequences for the mesopelagic prokaryotic community only recently explored.


We have studied processes related to both passive and active vertical transfer of DOC to the mesopelagic waters of the central Red Sea, one of the warmest oligotrophic marine basins in the world.


Passive seasonal transport of semi-labile DOC was estimated to contribute to ~20% of the oxygen respiration, mostly occurring at the lower epipelagic-upper mesopelagic boundary layer, while DOC actively supplied by daily migrating fish was identified to be of a labile nature (consumed at a mean rate of 2.1 µmol C L-1) and sustaining high HP growth efficiencies in the mesopelagic realm.


The consequences of this effect in the twilight zone for the global ocean, and the impact on global biogeochemical cycles is unknown.





Date and Time: Wednesday, December 11th, 12:00-13:00h

Place: IMEDEA Seminar Room