Swoboda, Steffen

Research interests:

• Forcing factors and transport mechanisms within the biological pump

• Small scale structures and dynamics in marine aggregates

• Marine aggregate formation

• Transparent exopolymeric particles (TEP) and their role in the marine carbon cycle

PhD project summary:

The biological pump is a key regulator for the export and burial of atmospheric CO₂ in the ocean and serves as nutrient supply for ecosystems at depth through the export of organic matter. This organic matter is commonly referred to as marine snow or marine aggregates and the efficiency at which these are exported at depth can be summarized by the interplay between its initial quantity, settling velocity and attenuation. Each of these factors in terms are affected by mechanisms of (trans)formation, translocation, degradation and preservation. This includes biologically mediated factors such as microbial degradation or zooplankton grazing and “repackaging” into fast settling fecal pellets, chemical factors such as adhesion forces or salinity gradients and physical factors including ballasting or current movements.

Generally, this export of organic matter via the biological pump is considered as a unidimensional system where horizontal movement is ignored. However, the relocation of organic matter by lateral advection is thought to be a crucial mechanism, especially in shelf systems which cover ~20% of global ocean production and often exhibit dynamic current regimes. My PhD will therefore focus on the role of lateral advection from shelf systems for the biological carbon pump in the open ocean by combining ship-based observations with mechanistic laboratory-based studies. This will enable us to relate large scale dynamics of the biological pump with the microenvironments which shape biological and physical processes inside aggregates. These small-scale processes determine the turnover and settling of individual aggregates, which again drive the large-scale transformation and transport of organic matter in the ocean.

Published articles:

Schmidt, M., Gerlach, G., Leo, E., Kunz, K. L., Swoboda, S., Pörtner, H. O., … Storch, D. (2017). Impact of ocean warming and acidification on the behaviour of two co-occurring gadid species, Boreogadus saida and Gadus morhua, from Svalbard. Marine Ecology Progress Series, 571, 183–191. https://doi.org/10.3354/meps12130