WP 7

Observation of carbon fluxes at sediment-water interfaces

 

Work Package Leaders

 

Description

Seafloor sediments serve as the ultimate sink for carbon provided by the biological pump. Moreover, the rain of particulate organic matter (POM) to the seafloor drives a range of microbial redox reactions that largely control the nutrient (nitrate, phosphate, iron) inventory of the global ocean.   Fluxes of POM reaching the seafloor are highly variable both in time and space. Since their spatial and temporal variability was never fully resolved, current budgets of carbon fluxes across the seabed are poorly constrained. 

In the REEBUS study area off Mauretania, a large part of this variability is related to mesoscale eddies enhancing the POM flux to the seabed. To explore the dynamics of benthic POM fluxes and degradation rates, we will develop and deploy observatories at the seabed that will register particle fluxes, benthic degradation rates and bottom current velocities over a full year with dayly or even higher solution for some properties. The spatial variability of POM deposition will be characterized using advanced seafloor mapping techniques (via ship, remotely operated vehicle (ROV, see figure 1) and (autonomous underwater vehicles (AUV, see figure 2) to derive bythemtric, seafloor backscatter and optical information (photomosaics) on different scales (mm to km). The obtained data sets will combine and detailed environmental DNA and biogeochemical analysis performed through TV-guided lander deployments. The data will be evaluated to provide the first regional budget of benthic carbon fluxes that fully resolve their temporal and spatial variability. For this we will apply machine learning techniques to relate very detailed singles spot analyses to larger areas as mapped by ship-based multibeam using a several layer nested approach (see figure 3). The occurrence and distribution of deep sea fauna and sediment appearances will be used to link our geochemical analyses with different habitat types (see figure 4).

 

General Questions and Research topics

  • Study the effects of eddies on benthic carbon turnover
  • Determine the spatial variability of benthic carbon turnover
  • Determine the temporal variability of benthic carbon turnover
  • Derive a regional budget of benthic carbon turnover in the REEBUS study area
  • Integrate data sets from different temporal and spatial scales to derive an integrated understanding

 

Figure 1. Deep sea observation systems with different landers, remotely operated vehicle (ROV) and a mooring. Picture credit: GEOMAR

 

Figure 2. Autonomous underwater vehicles (AUV) Abyss. Picture credit: Augustin, Kwasnitschka, Klischies (GEOMAR).

 

 

Klaus Wallmann Jens Greinert

 

 

Figure 3. Scale overarching analyses of different data sets for spatial extrapolations. A ship based bathymetric map (resolution 50 m); B autonomous underwater vehicles (AUV)  based batyhetry (3 m); C SideScan (1 m); D photomosaic (5 mm); E sampling (point that represents < 0.25 m2). Picture credit: GEOMAR.

Figure 4. Exemplary deep sea fauna. A Holothurin also called sea cucumber, B Brittle star and C Stalked sponge with an associated sea anemone. The grey gravel in the background are manganese nodules. Pictures were recorded in the Pacific Ocean 10° north-south of Hawaii in a water depht of approx. 4500 m. Picture credit: GEOMAR.