ALBERT

Description: The present dataset relates to a study that explored dissolved organic matter dynamics under three scenarios: a particle-free environment, a particle-enriched system with polystyrene microplastics, and a particle-enriched system with inorganic particles (water insoluble SiO₂). In part 1 of the experiment, natural marine organic matter was obtained by culturing a non-axenic strain of Chaetoceros socialis in 2 L flasks under each of three scenarios (1C = control, 2PS = polystyrene, 3S = silica). After the growth phase, filtered samples from the three flasks containing dissolved organic matter and bacteria were incubated separately in the dark in 4 replicates closed quartz cuvettes per treatment (total = 12 cuvettes, 28 mL capacity quartz cuvettes 10 cm path length, Hellma 120-QS, Quartz SUPRASIL, Hellma Analytics) at a temperature of of 20 °C ± 2 °C for 5 days to monitor changes in CDOM. In this phase, Chromophoric dissolved organic matter (CDOM), a bulk optical property, was monitored daily to examine changes in its quality and quantity and to compare degradation dynamics in the three systems (1C, 2PS and 3S). The dataset for part 2 reports CDOM absorption coefficient at 355 nm (a355, m⁻¹) as well as spectral slope parameters in different wavelengths as indicators of CDOM degradation processes and microbial activity: spectral slope S between 302 and 322 nm (S302-322, nm⁻¹), between 275 and 295 nm (S275-295, nm⁻¹), and between 350 and 400 nm (S350-400, nm⁻¹), as well as slope ratio SR, as SR = S275-295:S350-400.OC was estimated estimated in each cuvette from CDOM absorbance by applying the approach developed by Fichot and Benner (Fichot, C.G.; Benner, R. Geophys. Res. Lett. 2011, 38, doi:10.1029/2010GL046152) using culture specific parameters previously calibrated (Galgani, L. et al., Sci. Rep. 2018, 8, doi:10.1038/s41598-018-32805-4).

Description: The sea-surface microlayer (SML) is the ocean's uppermost boundary to the atmosphere and in control of climate relevant processes like gas exchange and emission of marine primary organic aerosols (POA). The SML represents a complex surface film including organic components like polysaccharides, pro- teins, and marine gel particles, and harbors diverse microbial communities. Despite the potential relevance of the SML in ocean-atmosphere interactions, still little is known about its structural characteristics and sen- sitivity to a changing environment such as increased oceanic uptake of anthropogenic CO2. Here we report results of a large-scale mesocosm study, indicating that ocean acidification can affect the abundance and activity of microorganisms during phytoplankton blooms, resulting in changes in composition and dynam- ics of organic matter in the SML. Our results reveal a potential coupling between anthropogenic CO2 emis- sions and the biogenic properties of the SML, pointing to a hitherto disregarded feedback process between ocean and atmosphere under climate change.

Description: The interface layer between ocean and atmosphere is only a couple of micrometers thick but plays a critical role in climate relevant processes, including the air-sea exchange of gas and heat and the emission of primary organic aerosols (POA). Recent findings suggest that low-level cloud formation above the Arctic Ocean may be linked to organic polymers produced by marine microorganisms. Sea ice harbors high amounts of polymeric substances that are produced by cells growing within the seaice brine. Here, we report from a research cruise to the central Arctic Ocean in 2012. Our study shows that microbial polymers accumulate at the air-sea interface when the sea ice melts. Proteinaceous compounds represented the major fraction of polymers supporting the formation of a gelatinous interface microlayer and providing a hitherto unrecognized potential source of marine POA. Our study indicates a novel link between sea ice-ocean and atmosphere that may be sensitive to climate change.