AUTHOR=Li Niu , Li Jingrou , Nie Ming , Wu Ming , Wu Jihua 

TITLE=Effects of grazing prohibition on nirK- and nirS-type denitrifier communities in salt marshes

JOURNAL=Frontiers in Microbiology

VOLUME=14

YEAR=2023

URL=https://www.frontiersin.org/journals/microbiology/articles/10.3389/fmicb.2023.1233352

DOI=10.3389/fmicb.2023.1233352

ISSN=1664-302X

ABSTRACT=<sec id="sec1"><title>Introduction</title><p>Grazing prohibition is an effective management practice to restore salt marsh functioning. However, the effects of grazing exclusion on denitrifying microbial communities and their controlling factors in salt marshes remain unclear.</p></sec><sec id="sec2"><title>Methods</title><p>In this study, we surveyed soil physicochemical properties and above- and below-ground biomass and using quantitative polymerase chain reaction and Illumina MiSeq high-throughput sequencing technology to determine the relative abundance, composition, and diversity of nitrite reductase <italic>nirS</italic>- and <italic>nirK</italic>-type denitrifying bacterial communities associated with grazing prohibition treatments and elevations.</p></sec><sec id="sec3"><title>Results</title><p>The abundance of <italic>nirS</italic>-type denitrifiers increased with grazing prohibition time, whereas the abundance of <italic>nirK</italic>-type denitrifiers remained unaltered. Moreover, <italic>nirS</italic>-type denitrifiers were more abundant and diverse than <italic>nirK</italic>-type denitrifiers in all treatments. Grazing prohibition significantly altered the operational taxonomic unit richness, abundance-based coverage estimator, and Chao1 indices of the <italic>nirS</italic>-type denitrifying bacterial communities, whereas it only minimally affected the structure of the <italic>nirK</italic>-type denitrifying bacterial community.</p></sec><sec id="sec4"><title>Discussion</title><p>The results imply that the <italic>nirS</italic> community, rather than <italic>nirK</italic>, should be the first candidate for use as an indicator in the process of salt marsh restoration after grazing prohibition. Substances of concern, total nitrogen, and salinity were the key environmental factors affecting the abundance and community composition of <italic>nirS</italic> and <italic>nirK</italic> denitrifiers. The findings of this study provide novel insights into the influence of the length of grazing prohibition and elevation on <italic>nirS</italic>- and <italic>nirK</italic>-type denitrifying bacterial community composition in salt marshes.</p></sec>