Bentho-pelagic coupling by sinking marine snow down to 6000m depth

Our current understanding of pelagic ecosystems decreases with depth and lags far behind that of the surface ocean. Our predictive understanding of the deep ocean role remains highly uncertain. Roughly 10 Pg of organic carbon enters the mesopelagic each year and approximately 90% of this organic carbon flux is utilized by the mesopelagic fauna (bacteria, zooplankton, midwater fishes) and 10% continue it’s long road to the abyss. The common understanding is that deep ecosystems are quiet and homogeneous. However, intermittent flux down to the abyss of phyto-detrital particles or evidence of deep vertical plankton and nekton migration, or strong variability at mesoscale or at bentho-pelagic interfaces  demonstrate that, contrary to the main paradigm, the abyssal ecosystem is dynamics. This fundamental lack of a predictive understanding means that although we are currently barely able to accurately predict the resilience of the mesopelagic ecosystem to changes in ocean conditions, predicting the fate abyssopelagic ecosystem is not possible at all. This is becoming increasingly critical for understanding the impacts of future climate changes on deep sea ecology. 

Underwater monitoring with cameras, down to 6000m, allow to cross the mesopelagic frontier down to the abyss and gain substantial understanding of biodiversity and carbon cycling at regional and global scales.

 

During the presentation, we will present, discuss and give perspectives to show that

- global scale monitoring by imaging systems to detect plankton and different types of particles is possible in the deep ocean

- specific coupling between hydrodynamics and plankton dynamics concours to focus the sinking of marine snow at mesoscale down to the abyss,

- vertical flux focusing has an impact on the deep sea life and this knowledge could be relevant at global scale

- mesopelagic and abyssopelagic layers are not only populated by the known midwater crustaceans, fishes and gelatinous metazoans but also by gigantic poorly know rhizarians that could play a role in the deep trophic web but also carbon flux.