3.10. Denitrification
Genes involving in all the steps of denitrification (nitrate reductions (narG, napA and napB), nitrite reduction (nirK and nirS), nitric oxide reduction (norB, C) and nitrous-oxide reduction (nosZ) were observed in the CAB of all the five copepod genera, but their relative proportions varied between the genera. The CAB of Temora spp. was found to have a high proportion of potential denitrification genes, especially narG, napA and napB genes, followed by the CAB of Pleuromammaspp., Centropages sp., Calanus spp. and Acartiaspp. (Figure S4).
Among the potential nitrite reductase genes, the proportion of nirK gene was higher than the nirS gene, in all the CAB of copepod genera (Figure S4). Furthermore, the proportion of nirK gene was high in the CAB ofTemora spp. and Acartia spp., whereas a high proportion of nirS was found in Pleuromamma spp. and Calanus spp. (Figure S4).
The next step in denitrification is the reduction of nitric oxide to nitrous oxide by norB, and norC genes. We also observed from the present analysis, we observed that the CAB of Temora spp. have a high proportion of norB gene followed by Acartia spp., while the proportion was low in Pleuromamma spp. followed by Calanusspp. and very low in Centropages sp. (Figure S4). Whereas the gene norC was found high in Pleuromamma spp. followed byCalanus spp. and found to have low in Temora spp. (Figure S4). The final reaction is denitrification, i.e. reduction of nitrous oxide to nitrogen by nosZ gene. The CAB of Acartia spp. followed byCalanus spp. have a high proportion of nosZ gene (Figure S4).