Figure 10. Meridional-Seasonal relationship between N2O concentration and in-situ oxygen in the BUS. Colour code represents the sum of NO3- and NO2- concentrations (in µmol L-1). In the summer season, the samples were marked with black circles. The best fitted model, accompanied by the corresponding r-squared value (r2) and the total number of samples (n) are also presented.
Our depth-cross section plots also reveal the potential consumption of N2O in the inner shelf of Lüderitz in summer campaign (Figure 5). This, in conjunction with nutrient depletion, points towards a possible denitrification process, leading to a breakdown in correlation.
Overall, there is a more heterogeneous distribution of N2O in the water column during summer, indicating a potential small-scale variability compared to the homogenous distribution observed in winter (Figures 3, 4, 5, and 9).
Our extended investigations into the primary factors influencing seasonal-spatial outgassing in the nBUS have revealed that the drivers of F CO2 and F N2O exhibit similarity within the BUS. Factor 1 accounts for approximately 60% of the total variance for both gases during the winter season. Despite oxygen displaying a negative correlation with various parameters such as wind speed, ΔCO2, ΔN2O, F CO2and F N2O, we propose that, particularly in winter, biological processes associated with oxygen depletion significantly contribute to the emissions of CO2 and N2O. This contribution becomes notably pronounced, particularly in conjunction with upwelling events, in regions adjacent to the coast in Kunene and Walvis Bay, where the highestp CO2 values were also observed (Figure 11).