Organic carbon isotopes in sediments have been frequently used to identify the source of organic matter.Here we present a study of organic δ^(13)C on two sediment profiles influenced by guano from Guangjin and Jinqin...Organic carbon isotopes in sediments have been frequently used to identify the source of organic matter.Here we present a study of organic δ^(13)C on two sediment profiles influenced by guano from Guangjin and Jinqing islands in the Xisha Archipelago,South China Sea.Organic matter from ornithogenic coral sand sediments has two main sources,guano pellets and plant residues,and their organic δ^(13)C(δ^(13)C_(OM)) are significantly different.Organic carbon δ^(13)C_(guano) is much higher thanδ^(13)C_(plants),and δ^(13)C_(OM)of bulk samples is intermediate.Based on a two-end-member mixing model,the proportions of guano-and plant-derived organic matter in the bulk samples were reconstructed quantitatively.The results showed that seabirds began to inhabit the islands around approximately1200-1400 AD,and that guano pellets have been an important source of soil organic matter since then.With the accumulation of guano-derived nutrients,plants began to develop prosperously on the islands in the last 200 years,which is reflected by the significant increase of plant-derived organic matter in the upper sediment layer.However,guano-derived organic matter decreased greatly in recent decades,indicating a rapid decrease in seabird population.Our results show that organic δ^(13)C can be effectively used to quantitatively determine different source contributions of OM to bulk ornithogenic coral sand sediments.展开更多
基金funded by the National Natural Science Foundation of China(Nos.41376124,41402148 and 41076123)the Fundamental Research Funds for the Central Universities(JZ2017HGTB0201)
文摘Organic carbon isotopes in sediments have been frequently used to identify the source of organic matter.Here we present a study of organic δ^(13)C on two sediment profiles influenced by guano from Guangjin and Jinqing islands in the Xisha Archipelago,South China Sea.Organic matter from ornithogenic coral sand sediments has two main sources,guano pellets and plant residues,and their organic δ^(13)C(δ^(13)C_(OM)) are significantly different.Organic carbon δ^(13)C_(guano) is much higher thanδ^(13)C_(plants),and δ^(13)C_(OM)of bulk samples is intermediate.Based on a two-end-member mixing model,the proportions of guano-and plant-derived organic matter in the bulk samples were reconstructed quantitatively.The results showed that seabirds began to inhabit the islands around approximately1200-1400 AD,and that guano pellets have been an important source of soil organic matter since then.With the accumulation of guano-derived nutrients,plants began to develop prosperously on the islands in the last 200 years,which is reflected by the significant increase of plant-derived organic matter in the upper sediment layer.However,guano-derived organic matter decreased greatly in recent decades,indicating a rapid decrease in seabird population.Our results show that organic δ^(13)C can be effectively used to quantitatively determine different source contributions of OM to bulk ornithogenic coral sand sediments.
