Abstract
Abstract. The colonization by a large number of sea animals, including penguins and seals, plays an important role in the nitrogen cycle of the tundra ecosystem in coastal Antarctica. However, little is known about the effects of sea animal colonization on ammonia-oxidizing archaea (AOA) and bacteria (AOB) communities involved in nitrogen transformations. In this study, we chose active seal colony tundra soils (SSs), penguin colony soils (PSs), adjacent penguin-lacking tundra soils (PLs), tundra marsh soils (MSs), and background tundra soils (BSs) to investigate the effects of sea animal colonization on the abundance, activity, and diversity of AOA and AOB in maritime Antarctica. Results indicated that AOB dominated over AOA in PS, SS, and PL, whereas AOB and AOA abundances were similar in MS and BS. Penguin or seal activities increased the abundance of soil AOB amoA genes but reduced the abundance of AOA amoA genes, leading to very large ratios (1.5×102 to 3.2×104) of AOB to AOA amoA copy numbers. Potential ammonia oxidation rates (PAORs) were significantly higher (P=0.02) in SS and PS than in PL, MS, and BS and were significantly positively correlated (P<0.001) with AOB amoA gene abundance. The predominance of AOB over AOA and their correlation with PAOR suggested that AOB play a more important role in the nitrification in animal colony soils. Sequence analysis for gene clones showed that AOA and AOB in tundra soils were from the Nitrososphaera and Nitrosospira lineages, respectively. Penguin or seal activities led to a predominance of AOA phylotypes related to Nitrososphaera cluster I and AOB phylotypes related to Nitrosospira clusters I and II but very low relative abundances in AOA phylotypes related to cluster II, and AOB phylotypes related to clusters III and IV. The differences in AOB and AOA community structures were closely related to soil biogeochemical processes under the disturbance of penguin or seal activities: soil C : N alteration and sufficient input of NH4+–N and phosphorus from animal excrements. The results significantly enhanced the understanding of ammonia-oxidizing microbial communities in the tundra environment of maritime Antarctica.
Highlights
Nitrification, the oxidation of ammonia to nitrate through nitrite, plays a pivotal role in the global biogeochemical nitrogen cycle (Nunes-Alves, 2016)
We investigated the abundance, potential activity, and diversity of soil ammoniaoxidizing archaea (AOA) and ammonia-oxidizing bacteria (AOB) in five tundra patches, including a penguin colony, a seal colony, the adjacent animal-lacking tundra, tundra marsh, and background tundra, where soil biogeochemical properties were subjected to the differentiating effects of sea animal activities
AOA amoA gene diversity was higher in penguinlacking tundra soils (PLs) and marsh soils (MSs) than in background tundra soils (BSs), whereas AOB amoA gene diversity was higher in seal colony tundra soils (SSs) and penguin colony soils (PSs) compared with that in adjacent animal-lacking tundra soils (Table S1)
Summary
Nitrification, the oxidation of ammonia to nitrate through nitrite, plays a pivotal role in the global biogeochemical nitrogen cycle (Nunes-Alves, 2016). Q. Wang et al.: Effects of sea animal colonization on soil AOB and AOA in Antarctica soils (Alves et al, 2013; Daebeler et al, 2017). Environmental drivers, including substrate concentration, oxygen availability, pH, and salinity, might be responsible for the different AOA and AOB abundances and distribution (Alves et al, 2013; Bouskill et al, 2012; Le Roux et al, 2008; Wang et al, 2015). There is still a large gap in our understanding of factors that control AOA vs AOB prominence, and the relationships between nitrification rates and ammonia-oxidizer dynamics need to be explored in Antarctica
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