MOBYDICK – Marine Ecosystem Biodiversity and Dynamics of Carbon around Kerguelen: an integrated view
Position of stations on the time-averaged map of March 2018 phytoplankton biomass (chlorophyll a concentration) over the study area during the MOBYDICK cruise.


The initial strategy was based on repeated sampling (~10 days interval) at 2 contrasted stations (M2 and M4) and additional sampling at 2 intermediate stations (M1 and M3). Station M2 is located in high–production iron fertilized waters above the Kerguelen plateau, and station M4 is located in low-production HNLC waters. Despite rough sea conditions encountered during the cruise (wind gusts up to 85 knots), the four stations have been sampled for every planned parameter. Station M1 was visited once only, M2 three times, M3 two times and M4 two times.

Chlorophyll map generated via NASA GIOVANNI application

The basic biogeochemical stocks (dissolved and particulate organic C, N, and P, particulate inorganic carbon, biogenic silica, inorganic nutrients) and flux parameters (community production and respiration) have been measured. C vertical export determined by the 234Th approach is presently under estimation.

Phytoplankton have been sampled using different gears:

  • A 35 μm mesh phytoplankton to sample the top 100 m of surface waters.
  • a bottenet (20 μm mesh sieve) mounted on a CTD rosette. 

Different gears have also been used to sample zooplankton (micro, meso and macro), and micronekton:

  • a zooplankton multinet of 100 μm mesh sieve to sample smaller species including the upper part of the microzooplankton, allowing vertical collections in successive water layers.
  • Traditional WP2, WP3 and Bongo plankton nets (330 μm)  to quantitatively estimate in situ abundance of mesozooplankton, macrozooplankton and gelatinous plankton.
  • a mesopelagic trawl for collection of micronekton.

    Sampling was performed at different times of the day to capture diel cycles. Species taxonomy, abundance and size distribution of zooplankton are currently determined using image analyses (Zooscan, microscopical observations).

A combination of instruments have been used to measure in situ distributions of (living and non-living) particles at high spatial resolution covering the size spectra from 1 μm to 15 cm:

  • Laser In Situ Scatterometer Transmissometer (LISST, 1-250 μm)
  • Underwater Vision Profiler (UVP, > 100 μm)
  • Laser Optical Particle Counter (LOPC, 1.5 mm to 35 mm)

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