Abstract
Expansion of penguin activity in maritime Antarctica, under ice thaw, increases the chances of penguin feces affecting soil microbiomes. The detail of such effects begins to be revealed. By comparing soil geochemistry and microbiome composition inside (one site) and outside (three sites) of the rookery, we found significant effects of penguin feces on both. First, penguin feces change soil geochemistry, causing increased moisture content (MC) of ornithogenic soils and nutrients C, N, P, and Si in the rookery compared to non-rookery sites, but not pH. Second, penguin feces directly affect microbiome composition in the rookery, not those outside. Specifically, we found 4,364 operational taxonomical units (OTUs) in 404 genera in six main phyla: Proteobacteria, Actinobacteria, Gemmatimonadetes, Acidobacteria, Chloroflexi, and Bacteroidetes. Although the diversity is similar among the four sites, the composition is different. For example, penguin rookery has a lower abundance of Acidobacteria, Chloroflexi, and Nitrospirae but a higher abundance of Bacteroidetes, Firmicutes, and Thermomicrobia. Strikingly, the family Clostridiaceae of Firmicutes of penguin-feces origin is most abundant in the rookery than non-rookery sites with two most abundant genera, Tissierella and Proteiniclasticum. Redundancy analysis showed all measured geochemical factors are significant in structuring microbiomes, with MC showing the highest correlation. We further extracted 21 subnetworks of microbes which contain 4,318 of the 4,364 OTUs using network analysis and are closely correlated with all geochemical factors except pH. Our finding f penguin feces, directly and indirectly, affects soil microbiome suggests an important role of penguins in soil geochemistry and microbiome structure of maritime Antarctica.
Highlights
Antarctica is unique due to its isolation from other continents, extreme climate, minimum of human activity, and indigenous organisms
We previously found that penguin rookery soils have different microbiome composition from pristine soils and soils colonized by human and seals (Wang et al, 2015)
Our results showed penguin feces dramatically changed soil geochemistry of the rookery area compared to that of three other sites
Summary
Antarctica is unique due to its isolation from other continents, extreme climate, minimum of human activity, and indigenous organisms. Animal feces could improve soil phosphorus (Zhu et al, 2014), organic matter, nitrogen (e.g., NO3−-N, and NO2−-N) (Legrand et al, 1998; Barrett et al, 2006; Aislabie et al, 2008). Penguins excrete organic nitrogen (OrN) and ammonia into soils (Mizutani and Wada, 1988; Zhu et al, 2010; Crittenden et al, 2015). Continued release of these C and N resources to the exposed soils will result in changed soil geochemistry and microbiome composition. The availability of nitrogen will further drive the function of these nitrogen-utilizing flora and change the composition of the entire flora (Pochana and Keller, 1999; Guyonnet et al, 2017)
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