Expeditions

RV POSEIDON cruise 425 (Fischer), Las Palmas - Las Palmas, 16.1.-30.1.2011 (scheduled)

During the scheduled cruise to the coastal upwelling area off Cape Banc (Mauritania) we plan to conduct particle flux studies using moored sediment traps, free-drifting sediment traps (see pictures to the right), in situ pumps, water samplers and the multiple plankton net for the collection of zooplankton.

Abstract (proposal by Fischer, Iversen and Mollenhauer)
The coastal upwelling area off NW Africa is a highly dynamic production system where organic material is transported offshore via filaments and eddies. This transport and the decay of organic carbon in the water column are dependent on the sinking velocities of larger ‘marine snow’ particles and zooplankton fecal pellets, which in turn are controlled by various ballast minerals. During the cruise, we plan to perform maintenance and exchange of instrumentation at the two mooring systems CB and CBi off Cape Blanc (Mauritania), which are equipped with sediment traps, oceanographic instruments, and optical systems attached to a technical platform (MSD=Multi-Sensor-Device). The MSD-platform with a video system has been deployed the past two years and provided novel data on bi-daily particle concentrations and size-distributions at 1200 m depths at site CBi where trap fluxes are recorded with approximately weekly resolution. Long-term records of particle fluxes have already been obtained since 1988 at the mesotrophic site CB and since 2003 at the eutrophic site CBi, serving to document potential changes in the ecosystem of the NW African coastal upwelling. Additionally, short-term flux changes, the composition and decay of larger particles will be studied using free-drifting sediment traps deployed at the eutrophic station CBi. We plan to obtain high vertical and horizontal resolution of particle distributions at 11 stations with vertical imaging profiles using a 16 MPixel camera and turbidity sensor. At selected key stations, the composition of organic material, in particular the concentrations of individual biomarkers in relation to water depth and particle sinking velocities as well as the bacterial populations on sinking particles shall be investigated. Direct measurements of aggregate size-specific degradation, sinking velocities, microbial degradation, bacterial community, and chemical composition will be performed on aggregates re-formed from in situ collected water samples in roller tanks and related to the in situ measurements. By combining in situ particle observations, experimental microbiological studies, and organic-geochemical analysis in a high resolution transport model (with aggregation and NPZD-ecosystem modules), we expect to gain a better understanding of particle transport, aggregation and disaggregation as well as remineralization processes in the water column on longer time scales.

During the cruise, we plan to perform maintenance and exchange of instrumentation at the two mooring systems CB and CBi off Cape Blanc, Mauritania. Long-term records of particle fluxes have already been obtained since 1988 at site the mesotrophic site CB and since 2003 at the eutrophic site CBi, serving to document potential changes in the ecosystem of the NW African coastal upwelling. Additionally, short-term flux changes, the composition and decay of larger particles will be studied using free-drifting sediment traps. We plan to study the regional and temporal variability of particle distribution and dynamics and the remineralisation of organic carbon in the water column off Cape Blanc and north of the Cape Verde Islands. The composition of organic material, in particular the concentrations of individual biomarkers in relation to water depth and particle sinking velocities as well as the bacterial populations on sinking particles shall be investigated. The comparison between particles from Cape Blanc and Cape Verde (very high dust input) will allow investigations on the influence of ballast minerals on particle composition and bacterial populations on the particles and their degradation. To do so, we intend to use water samplers, CTD’s (with oxygen and turbidity sensors), optical systems, in situ-pumps as well as the ROV Cherokee for the observation of the in situ behaviour of larger particles. Experimental aggregation using roller tanks will be another important aspect for our investigations. By combining in situ particle observations, experimental microbiological studies, organic-geochemical analysis and satellite observations and the application of a high resolution transport model (with aggregation and NPZD-ecosystem modules), we expect to gain a better understanding of particle transport scenarios, aggregation and disaggregation as well as remineralization processes in the water column shall.

RV Poseidon cruise 396 (Fischer), Las Palmas - Las Palmas

Abstract (proposal Fischer, Mollenhauer)
The coastal upwelling off NW Africa is a highly dynamic production system where organic material is transported offshore via filaments and eddies. This transport and the decay of organic carbon in the water column are at least partly dependent on the sinking rates of larger particles which in turn are controlled by various ballast minerals. During the cruise (24.2. to 8.3.2010), we performed maintenance on and exchange instrumentation at the two mooring systems CB and CBi off Cape Blanc, Mauritania (Figure right), which were equipped with sediment traps, oceanographic instruments and optical systems attached to a technical platform (MSD). Long-term records of particle fluxes have already be obtained from 1988 at site CB and from 2003 at site CBi, serving to document potential changes in the NW African coastal upwelling. Additionally, studied the regional and temporal variability of particle distribution and dynamics as well as the remineralisation of organic carbon in the water column at 4-6 stations along an E-W transect (Figure right). To do so, we used water samplers, CTD’s, optical systems and in situ pumps. With the combination of in situ particle observations, experimental microbiological studies, organic-geochemical analysis and satellite observations and the application of a high resolution transport model (with an aggregation and NPZD module), particle transport scenarios, aggregation and remineralization processes in the water column shall be studied.

MSM Merian cruise 11 Leg 2 (Bickert), Dakar - Las Palmas de Gran Canaria

On March 15th, MSM Merian cruise 11 Leg 2 started in Dakar (Senegal). Sediment trap moorings were recovered and redeployed at the stations CB and CBi of Cape Blanc, Mauritania, complemented by an intense study program of the particle fluxes in that area. About 5 stations were dedicated to the sampling of planktonic orgamisms of the upper water column. These investigations complement already existing studies of particle transport. Such research is important with respect to production and settling of particles and hence their use as proxies in paleoceanography. Water samplers combined with a CTD device and a fluorescence sensor were used to sample the water column. In-situ pumps helped to sample the suspended matter. Radiometric datings of specific organic compounds were used to constrain the sources and transport mechanism of the organic material. A further objective was the direct determination of the sinking velocity of different particles, which is still a matter of intense debate. Diachronous vertical camera profiling along an E-W transect over the sediment trap sites CB and CBi aimed at documenting the variability of the particle distribution on short time scales. Further mooring work was done in the working Area F north of Canary Islands (CI/ESTOC). Finally, wind-blown dust was collected throughout the entire cruise to better constrain the provenance of the terrigenous material. MSM Merian cruise 11 Leg 2 ended in Las Palmas de Gran Canaria on April 9th, 2009.

RV POSEIDON cruise 365 Leg 1 (Ruhland) and 2 (Fischer): Las Palmas - Las Palmas

The cruise was divided into two parts, one into the area of the ESTOC and DOLAN site north of the Canary Islands (13.4.-16.4.2008). The second part (18.4. - 29.4.2008) sailed southwards into the Mauritanian upwelling area off Cape Blanc (see figure to the right). Two sediment trap moorings were served, one equipped with a platform containing a special CTD with various sensors and a video camera system. At 7 sites, the water column was sampled with the ROV Cherokee, the ParCa-CTD and NISKIN water collectors. Dust samplers collected Saharan dust during transit times.

Deployment of the ROV Cherokee equipped with a settling chamber (at the frontal part) for in situ meansurements of particle settling rates.

Cruise track of RV M.S. MERIAN 04b (Fischer)

Cruise track of RV M.S. MERIAN cruise 04b (Las Palmas - Las Palmas, 19.3. - 1.4.2007). In area A, the DOLAN data buoy and the ESOTC mooring were retrieved and redeployed. On the Cape Blanc area B, we recovered and redeployed two moorings and performed additional optical, chemical, micropaleontological and microbiological studies in the water column.

The DOLAN data buoy during the recovery 60 nm north of the Canary Islands

Satellite chlorophyll on march 16, 2007 in the study area B (upper right figure) in the Cape Blanc filament (off Mauretania). GeoB stations and the mooring sites are also shown.

Cruise track of RV POSEIDON 344-1 (Fischer) and 344-2 (Ruhland)

Cruise track and study area off Cape Blanc (Mauretania) during RV POSEIDON cruise 344-1 (Las Palmas - Las Palmas, 20.10. - 2.11.2006). Two sediment trap moorings have been exchanged and water and particle samples have been recovered at 5 sites in an E-W transect. The particle camera ParCa and the ROV Cherokee have been launched at several sites.