干旱区生态环境知识资源中心

We analyzed delta N-15 in both acid-treated and untreated sediment profiles fromMcMurdo Sound of the Ross Sea region, East Antarctica thatwere influenced by penguin guano. The difference between treated and untreated delta N-15 (Delta N-15) was significant in three profiles which were heavily impacted by guano, and minor in two profiles with less guano influence. We determined that the total nitrogen in the sediments is primarily derived from penguin guano and algae, and used an N-species test to explain the variation of Delta N-15 in two profiles. It was found that post-depositional decomposition and ammonia volatilization, which have important roles in the cold and arid environment of East Antarctica, would render an elevated delta N-15 through kinetic isotopic fractionation in the inorganic nitrogen from guano. N-species analysis revealed that the percentage of inorganic nitrogen in total nitrogen, indicative of the degree of guano influence, is the key factor controlling Delta N-15 in the sediments. This hypothesis successfully explained the nitrogen isotopic composition in the remaining three sediment profiles. We conclude that the parameter Delta N-15, rather than traditionally used untreated delta N-15, can be taken as an effective proxy for the strength of avian influence on ornithogenic sediments in East Antarctica. (C) 2013 Elsevier B.V. All rights reserved.