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).