Potential contributions of nitrifiers and denitrifiers to nitrous oxide sources and sinks in China's estuarine and coastal areas

[摘要] Nitrous oxide (N 2 O) is an important ozone-depletinggreenhouse gas produced and consumed by microbially mediated nitrificationand denitrification pathways. Estuaries are intensive N 2 O emissionregions in marine ecosystems. However, the potential contributions ofnitrifiers and denitrifiers to N 2 O sources and sinks in China'sestuarine and coastal areas are poorly understood. The abundance andtranscription of six key microbial functional genes involved innitrification and denitrification, as well as the clade II-type nosZ gene-bearing community composition of N 2 O reducers, were investigatedin four estuaries spanning the Chinese coastline. The results showed thatthe ammonia-oxidizing archaeal amoA genes and transcripts were more dominant inthe northern Bohai Sea (BS) and Yangtze River estuaries, which had lownitrogen concentrations, while the denitrifier nirS genes and transcripts weremore dominant in the southern Jiulong River (JRE) and Pearl River estuaries,which had high levels of terrestrial nitrogen input. Notably, the nosZ clade IIgene was more abundant than the clade I-type throughout the estuaries exceptfor in the JRE and a few sites of the BS, while the opposite transcriptdistribution pattern was observed in these two estuaries. The gene andtranscript distributions were significantly constrained by nitrogen andoxygen concentrations as well as by salinity, temperature, and pH. The nosZ cladeII gene-bearing community composition along China's coastline had a high level ofdiversity and was distinctly different from that in the soil and in marineoxygen-minimum-zone waters. By comparing the gene distribution patternsacross the estuaries with the distribution patterns of the N 2 Oconcentration and flux, we found that denitrification may principallycontrol the N 2 O emissions pattern.

[学科分类] 大气科学