Work Package 5

Particle size distribution and export fluxes and zooplankton-particle interactions

Work Package Leaders


Sinking of organic material from the surface to the deeper ocean depends on the size and characteristics of biogenic particles, which vary strongly with time and location. It determines the period over which biomass is available as food for higher trophic levels: once particles sink into the oxygen minimum zone, they will be inaccessible for most marine fish species. Because particle sinking moderates the horizontal displacement of organic matter, it also causes “nutrient-trapping” on the shelf and keeps organic matter or recycled nutrients close to the shore.

General Questions and Research topics

With measurements of particle concentrations, their size distribution and composition in the open ocean and during a mesocosm experiment we aim to investigate the following questions:

(1) How do particle flux and composition vary with upwelling intensity?

(2) How much primary production is exported into suboxic waters, instead of being transferred to higher trophic levels?

(3) How do particle size, flux, and zooplankton community composition vary with time (mesocosms) and space (ship-based).


The data sets obtained in this project, complemented by already available data of UVP (Underwater Vision Profiler) and zooplankton catches, will help to calibrate the size-resolved regional model employed in WP6.

Dr. Rainer Kiko mounts the UVP5 on a CTD-Rosette
(photo: Sunke Schmidtko, GEOMAR)


Dr. Jan Taucher deploys a special underwater camera into a mesocosm
(photo: Tim Boxhammer)

The UVP5, a camera system for plankton
and particle imaging that can be deployed down to 6000 m depth (photo: R. Kiko, GEOMAR)


Reinhard Koch

Rainer Kiko
Photo: Jan Steffen (GEOMAR)

Helena Hauss

Jan Taucher

Iris Kriest