Application of 515N to trace the impact of penguin guano on terrestrial and aquatic nitrogen cycles in Victoria Land, Ross Sea region, Antarctica

摘要

Penguin colonies in Antarctica offer an ideal "natural laboratory" to investigate ecosystem function and the nitrogen (N) cycle. This study assessed the spatial distribution of penguin-derived N from guano and quantitatively assessed its impact on plant N utilization strategies in Victoria Land, Ross Sea region, Antarctica. Soil, moss, and aquatic microbial mats were collected inside and outside an active Adelie penguin (Pygoscelis adeliae) colony and analyzed for δ~(15)N of total and inorganic nitrogen (NH_4~+-N and NO_3~--N). The soil total nitrogen (TN), NH_4~+-N, and NO_3-N concentrations, as well as their δ~(15)N values were significantly higher in guano-impacted areas than those in guano-free areas, verifying that guano is an important N source at and near penguin colonies. However, even far from the penguin colonies, soil δ~（15)N values resembled those in penguin colonies, suggesting strong spatial impacts of penguin-derived N. The moss impacted by guano was more enriched in δ~(15)N than in guano-free areas. The δ~(15)N values of NH_4~+-N and NO_3-N in soils covered with moss revealed that the moss might prefer inorganic N in the absence of guano, while the dissolved organic N would become an important source for moss growing on ornitho-genic soils. Aquatic microbial mat samples near penguin colonies were ~(15)N-enriched, but ~(15)N-depleted at upland sites.