Recent results

Preservation and observation of sinking marine snow

We deployed a drifting buoy equipped with two particle trap arrays (four cylindrical traps on each) within the Cape Blanc filament over 2.5 days in spring 2011 (6 nm drift). A satellite tracking system (GlobalTrack, South-Africa) reported a GPS position of the drifter every two hours. The trap depths were 100 m and 400 m. For each trap depth, two of the collection cylinders had a viscous gel at the bottom to catch particles without destroying their original structure. The material caught in the gel will be used to estimate the particle size spectra of settling material via photographic analyses.

The figure to the right shows an image form the material collected by the sampling cups filled with gels after recovery. The left hand picture shows the material collected at 100 m depth and the right hand side is a picture of the material collected at 400 m depth. A scale bar is provided in the lower left. It is observed that most of the particles collected at 100 m were fecal pellets from krill and copepods. At 400 m depth, most of the particles were small and spherical and only a minor part of the total collected material consisted of intact fecal pellets (Iversen et al., unpubl.)

Nepheloid layers and biomarkers

The figure to the right shows the distribution of nepheloid layers (detected with the CTD-turbidity sensor and ParCa) and the Tex86-values of suspended matter from the water-column and from surface sediment (E-W-transect off Cape
Blank, Mauritania, RV-Poseidon cruise POS 396, Feb-Mar 2010; Basse et al. unpubl.)

Particle data from a video system (MSD platform) and mass fluxes over two annual cycles

The picture to the right shows a comparison of sediment trap fluxes (upper panels) with particle data derived from a moored video camera system (lower panels) from off Cape Blanc, NW-Africa. It appears that the number of particles determines the mass fluxes. Particle sizes (ESD), however, are generally low and do not change that much during the two annual cycles of observation (Nowald et al., unpubl.).

Dust record off Cape Blanc since 1988

The figure to the right shows a time-series of the percentage of dust (on a seasonal basis) in particles collected with sediment traps from 1988 to 2010. Data are from deep ocean sediment traps from the CB site located about 200nm off Cape Blanc, Mauritania. It appears that the contribution of Saharan dust in the settling particles decreases since 1988 in this area (Fischer et al., unpubl.)

Bacterial distribution and abundance in the water column

Preliminary data for a depth profile of bacterial abundance was done during the RV Poseidon cruise 396 is shown on the right. A decrease of total cell counts with depth was found while bacterial abundance showed fluctuations corresponding largely to the particle nepheloid layers in the water column, obtained with optical systems and turbidity sensors (S. Thiele, MPI, unpubl. data).