Abstract
In maritime Antarctica, sea animals, such as penguins or seals, provide a large amount of external nitrogen input into tundra soils, which greatly impact nitrogen cycle in tundra ecosystems. Denitrification, which is closely related with the denitrifiers, is a key step in nitrogen cycle. However, effects of sea animal activities on tundra soil denitrification and denitrifier community structures still have received little attention. Here, the abundance, activity, and diversity of nirS‐ and nirK-encoding denitrifiers were investigated in penguin and seal colonies, and animal-lacking tundra in maritime Antarctica. Sea animal activities increased the abundances of nirS and nirK genes, and the abundances of nirS genes were significantly higher than those of nirK genes (p < 0.05) in all tundra soils. Soil denitrification rates were significantly higher (p < 0.05) in animal colonies than in animal-lacking tundra, and they were significantly positively correlated (p < 0.05) with nirS gene abundances instead of nirK gene abundances, indicating that nirS-encoding denitrifiers dominated the denitrification in tundra soils. The diversity of nirS-encoding denitrifiers was higher in animal colonies than in animal-lacking tundra, but the diversity of nirK-encoding denitrifiers was lower. Both the compositions of nirS‐ and nirK-encoding denitrifiers were similar in penguin or seal colony soils. Canonical correspondence analysis indicated that the community structures of nirS‐ and nirK-encoding denitrifiers were closely related to tundra soil biogeochemical processes associated with penguin or seal activities: the supply of nitrate and ammonium from penguin guano or seal excreta, and low C:N ratios. In addition, the animal activity-induced vegetation presence or absence had an important effect on tundra soil denitrifier activities and nirK-encoding denitrifier diversities. This study significantly enhanced our understanding of the compositions and dynamics of denitrifier community in tundra ecosystems of maritime Antarctica.
Highlights
Nitrogen (N) is an essential element for the biosynthesis of key cellular components, such as proteins and nucleic acids, in all organisms (Kuypers et al, 2018)
NirS- and nirK-encoding denitrifiers were detected in all tundra soils, the abundances of nirSencoding denitrifiers were significantly higher than those of nirK-encoding denitrifiers (Figure 2), which agreed with the results from other environments, such as the Yellow River
The nirK gene abundances (7.4 × 102–6.2 × copies g−1) were significantly lower compared with nirS gene, consistent with those (103– copies g−1 soil) in soils from King Sejong Station in Antarcitc (Jung et al, 2011), and Svalbard (Hayashi et al, 2018)
Summary
Nitrogen (N) is an essential element for the biosynthesis of key cellular components, such as proteins and nucleic acids, in all organisms (Kuypers et al, 2018). Penguin and seal colonies have a significant impact on tundra soil bacterial community structure (Ma et al, 2013; Zhu et al, 2015a), and the abundances, community compositions, and activities of ammonia oxidation archaea (AOA) and bacteria (AOB) are closely related to sea animal activities (Wang Q. et al, 2019). Our main objectives were (1) to examine potential denitrification rates in tundra soils; (2) to investigate the abundance, diversity, and community structures of nirS- and nirK-encoding denitrifiers; and (3) to determine effects of sea animal activities and environmental variables on the abundances, community compositions, and activities of the denitrifiers in tundra soils of maritime Antarctica
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