Status: this preprint was under review for the journal BG but the revision was not accepted.
Estimation of nutrient contributions from the ocean across a river basin using stable isotope analysis
K. Nakayama,Y. Maruya,K. Matsumoto,M. Komata,K. Komai,and T. Kuwae
Abstract. Total nitrogen (TN), which consists of total particulate nitrogen (TPN) and total dissolved nitrogen (TDN), is transported with not only in river channels but also across the entire river basin, including via ground water and migratory animals. In general, TPN export from an entire river basin to the ocean is larger than TDN in a mountainous region. Since marine derived nutrients (MDN) are hypothesized to be mainly transported as suspended matters from the ground surface, it is necessary to investigate the contribution of MDN to the forest floor (soils) in order to quantify the true role of MDN at the river ecosystem scale. This study investigated TN export from an entire river basin, and also we estimated the contribution of pink (Oncorhynchus gorbuscha) and chum salmon (O. keta) to total oceanic nitrogen input across a river basin. The maximum potential contribution of TN entering the river basin by salmon was found to be 23.8 % relative to the total amount of TN exported from the river basin. The contribution of particulate nitrogen based on suspended sediment from the ocean to the river basin soils was 22.9 % with SD of 3.6 % by using stable isotope analysis (SIA) of nitrogen (δ15N).
Received: 24 Oct 2015 – Discussion started: 11 Nov 2015
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We conducted field experiments to understand the recycling of total nitrogen from the ocean across an entire river basin using stable isotope analysis. To our best knowledge, for the world's first we estimated the marine derived nutrients recycling rate. This study also demonstrates that TN may be recycled from the ocean to the river basin not only directly due to runs of salmon, but also indirectly due to subsequent transportation processes, such as sea eagles feeding and defecation.
We conducted field experiments to understand the recycling of total nitrogen from the ocean...
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