Premium
Fluvial transport of carbon along the river‐to‐ocean continuum and its potential impacts on a brackish water food web in the Iwaki River watershed, northern Japan
Author(s) -
Iwata Tomoya,
Suzuki Takao,
Togashi Hiroyuki,
Koiwa Naoto,
Shibata Hideaki,
Urabe Jotaro
Publication year - 2013
Publication title -
ecological research
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.628
H-Index - 68
eISSN - 1440-1703
pISSN - 0912-3814
DOI - 10.1007/s11284-013-1047-8
Subject(s) - dissolved organic carbon , environmental science , watershed , hydrology (agriculture) , total inorganic carbon , carbon sink , carbon cycle , carbon fibers , brackish water , environmental chemistry , geology , carbon dioxide , ecology , chemistry , ecosystem , oceanography , salinity , climate change , geotechnical engineering , machine learning , computer science , biology , materials science , composite number , composite material
Riverine transport of dissolved inorganic carbon (DIC) from land to the ocean is an important carbon flux that influences the carbon budget at the watershed scale. However, the dynamics of DIC in an entire river network has remained unknown, especially in mountainous Japanese watersheds. We examined the effects of watershed land use and geology on the transports of inorganic carbon as well as weathered silica (Si) and calcium (Ca) in the Iwaki River system where agricultural and residential areas have developed in the middle and lower parts of the watershed. The concentration and stable carbon isotope ratios (δ 13 C) of DIC showed the longitudinal increase of 13 C‐depleted inorganic carbon along the river. As a result, most streams and rivers were supersaturated in dissolved CO 2 that will eventually be emitted to the atmosphere. The possible origin of 13 C‐depleted carbon is CO 2 derived from the decomposition of organic matter in agricultural and urban landscapes, as well as from in‐stream respiration. In addition, agricultural and urban areas, respectively, exported the large amount of dissolved Si and Ca to the rivers, suggesting that CO 2 increased by respiration accelerates the chemical weathering of silicate and carbonate materials in soils, river sediments, and/or urban infrastructure. Furthermore, riverine bicarbonate flux is likely to enter shell carbonates of Corbicula japonica, an aragonitic bivalve, in the downstream brackish lake (Lake Jusan). These results revealed that the flux of DIC from the human‐dominated watersheds is a key to understanding the carbon dynamics and food‐web structure along the land‐to‐river‐to‐ocean continuum.