ALBERT

Description: Redfield ratios of remineralization are calculated based on chemical data analysis on isopycnal surfaces. The concentrations of dissolved inorganic carbon used in this study were corrected for the anthropogenic CO2 content as estimated with a back-calculation technique. The corrections increased the apparent carbon remineralization by 25-30%, thus proving important for the reliable estimation of Redfield carbon ratios in the presence of anthropogenic CO2. Best estimates from this study largely confirm the more recently published Redfield ratios of remineralization. The following results were obtained for the latitude range 3-41°N along 20-29°W in the Northeast Atlantic Ocean: Corg: P ratio = 123 ± 10; Corg : N ratio = 7.2 ± 0.8; -O2 :Corg ratio = 1.34 ± 0.06; -O2 : P ratio = 165 ± 15; N: P ratio = 17.5 ± 2.0. These ratios are in close agreement with the average composition of phytoplankton and represent respiration of organic matter consisting on average of 52% protein, 36% polysaccharide, and 12% lipid.

Description: Rivers are an important transport route of anthropogenic litter from inland sources toward the sea. A citizen science approach was used to evaluate the litter pollution of rivers in Germany: schoolchildren within the project “Plastic Pirates” observed floating macrolitter at 282 sites and took meso-/microplastic samples (i.e. particles 1 mm - 25 mm) at over 164 sites across the entire country during the years 2016 and 2017. Floating macrolitter quantities ranged from 0 to 8.25 items m -1 h -1 (average of 0.34 ± 0.89 litter items m -1 h -1 ) and floating macrolitter was sighted at 54% of sampling sites. The quantities of floating meso-/microplastics ranged from 0 to 220 particles h -1 (average of 6.86 ± 24.11 meso-/microplastics h -1 ). They were present at 57% of the sampling sites. Given that only particles 〉 1 mm were sampled and analyzed, the pollution of rivers in Germany by microplastics is likely a ubiquitous problem, regardless of the size of the river. We identified six plastic pollution hotspots where 60% of all meso-/microplastics collected in the present study were found. The composition of the particles at these hotspots indicates plastic producers and possibly the construction industry and wastewater treatment plants as point sources. An identification of litter hotspots would enable specific mitigation measures, adapted to the respective source, and thereby prevent the release of large quantities of small plastic particles in rivers. The adopted large-scale citizen science approach was especially suitable to detect pollution hotspots by sampling a variety of rivers, large and small, and enabled a national overview of litter pollution in German rivers.

Description: Redfield stoichiometry has proved a robust paradigm for the understanding of biological production and export in the ocean on a long-term and a large-scale basis. However, deviations of carbon and nitrogen uptake ratios from the Redfield ratio have been reported. A comprehensive data set including all carbon and nitrogen pools relevant to biological production in the surface ocean (DIC, DIN, DOC, DON, POC, PON) was used to calculate seasonal new production based on carbon and nitrogen uptake in summer along 20°W in the northeast Atlantic Ocean. The 20°W transect between 30 and 60°N covers different trophic states and seasonal stages of the productive surface layer, including early bloom, bloom, post-bloom and non-bloom situations. The spatial pattern has elements of a seasonal progression. We also calculated exported production, i.e., that part of seasonal new production not accumulated in particulate and dissolved pools, again separately for carbon and nitrogen. The pairs of estimates of 'seasonal new production' and 'exported production' allowed us to calculate the C : N ratios of these quantities. While suspended particulate matter in the mixed layer largely conforms to Redfield stoichiometry, marked deviations were observed in carbon and nitrogen uptake and export with progressing season or nutrient depletion. The spring system was characterized by nitrogen overconsumption and the oligotrophic summer system by a marked carbon overconsumption. The C : N ratios of seasonal new as well as exported production increase from early bloom values of 5-6 to values of 10-16 in the post-bloom/oligotrophic system. The summertime accumulation of nitrogen-poor dissolved organic matter can explain only part of this shift.