Science

The focus of expedition is to study marine snow.

Life in the surface ocean generates a vast amount of sinking organic material, molts, exudates and other remnants, all byproducts of the race to outcompete all other life for resources.

Biological communities vary geographically, and with depth, and although they all feed on and leave their unique impact on marine snow, they don’t all do it in the same manner.

How the varying structure of biological communities impacts marine snow, the vertical flux of organic carbon, and ultimately the ocean’s capacity to regulate atmospheric CO2, is a key question for the expedition.

… and the more technical part:

The biological communities will be characterised using water bottles to collect the microscopic plants, the phytoplankton, and nets and a Video Plankton Recorder for the zooplankton.

How does surface mixing in a dynamic ocean alter the phytoplankton communities, as well as their rate of production, will be one critical question. Phytoplankton are also altered by grazers, the zooplankton, which are very mobile vertically. During the expedition, 335micron mesh MultiNets will sample every 5 meter depth horizon between the surface and 1 000 meters, and day and night sampling will track the vertical migration of zooplankton.

Such high resolution sampling will also generate a wealth of measurements on zooplankton biomass, taxonomic information about the changing communities, and their grazing impact on both phytoplankton and the settling marine snow.

The leftovers of grazing will also be analysed. Collection of live zooplankton from the WP2 Net will allow us to determine faecal pellet production rates of the dominant species in the region. We will compare faecal pellet production rates with two other methods, PELAGRA floating sediment traps and in the Marine Snow Catcher, hoping to obtain consistent results of a process that is otherwise challenging to quantify.

The Marine Snow Catcher, essentially a large water bottle, is a specifically designed equipment to sample the large sinking particles (> 0.5 mm) that constitute marine snow. The particles will be photographed and their sinking rates measured.

Specially prepared gels placed in the collection cups of the PELAGRA free floating traps will also fix the fragile marine snow particles in a matrix without changing their shape or structure. By deploying 6 free floating PELAGRA traps simultaneously between 100 and 800 meters for 3 days, we can follow the evolution of marine snow as it sinks out of the surface.

Results from the latest edition of “Down to the Twilight Zone” expedition will then be put into longer term temporal context, provided by the PAP observatory providing data every few hours on water column properties and the long term downward flux of carbon at 3000m.

We hope you can join us

Richard Lamp itt Chief Scientist on the James Cook “Down to the Twilight Zone”

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