TY - JOUR
T1 - Assimilation of terrigenous organic matter via bacterial biomass as a food source for a brackish clam, Corbicula japonica (Mollusca
T2 - Bivalva)
AU - Yamanaka, Toshiro
AU - Mizota, Chitoshi
AU - Maki, Yonosuke
AU - Matsumasa, Masatoshi
N1 - Funding Information:
The sulfur isotopic analysis was conducted at the Institute of Study for the Earth's Interior, Okayama University, as a joint research program. We are grateful to Professor Minoru Kusakabe for providing laboratory facilities. We also thank Mr. N. Satoh, Mr. S. Kumagai, and Mr. A. Kumagai for their extensive help with fieldwork and in stimulating discussion. We are also grateful to Prof. J. Hobbs of Iwate Medical University for his comments and assistance in improving the English in this manuscript. We appreciate the valuable comments given by two anonymous reviewers and editorial handling by Dr. Bianchi, Editor of this journal. This work is supported in part by the River Environmental Fund in charge of the Foundation of River and Watershed Environment Management, Japan, and by a Grant-in-Aid for Scientific Research (B) from the Japan Society for the Promotion of Science (No. 14380262 ).
PY - 2013/7/10
Y1 - 2013/7/10
N2 - Corbicula japonica collected from the Kitakami River estuary, northeastern Japan, showed lower δ34S values in soft-body parts (+1.7 to+11.0‰) than the ambient seawater sulfate sulfur (+21‰), and this value gradually decreased at successive sites up to 15.8km upstream from the river mouth. Previous study using carbon and nitrogen isotopes suggests that the bivalve nonselectively assimilates particulate organic matter of marine and terrestrial origin by filter feeding. This pattern in δ34S values may indicate a considerable contribution of a food source derived from terrigenous organic matter, which has low δ34S values close to 0‰, and the bivalve has been reported to have cellulase and hemicellulase activities. Unique fatty acids (iso 17:0 and anteiso 17:0 acids), both characteristic of sulfate-reducing bacteria, were observed in the salt-free, soft-body parts of the bivalve. The concentration of monounsaturated fatty acids, possibly derived from bacteria, was also high. Trace amounts of a polyunsaturated fatty acid (20:5ω3) specific to dinoflagellates were detected. In Corbicula habitats, reductive sandy layers with ample sulfides that were sporadically intercalated into the oxidative sandy sediment were often observed. The stable isotopic signatures of sediment sulfides (acid-volatile sulfide) and associated pore-water sulfates were-8.9 to+8.6‰ and+22.4 to+26.3‰, respectively, indicating the existence of bacterial sulfate-reducing activity and thiobios biomass. These isotopic signatures of the sediment, with the fatty acid composition of the bivalve, confirm the importance of a food source derived from bacteria belonging to the thiobios in the substrate sediments via pedal feeding, rather than direct digestion of terrigenous organic matter, in this estuarine ecosystem.
AB - Corbicula japonica collected from the Kitakami River estuary, northeastern Japan, showed lower δ34S values in soft-body parts (+1.7 to+11.0‰) than the ambient seawater sulfate sulfur (+21‰), and this value gradually decreased at successive sites up to 15.8km upstream from the river mouth. Previous study using carbon and nitrogen isotopes suggests that the bivalve nonselectively assimilates particulate organic matter of marine and terrestrial origin by filter feeding. This pattern in δ34S values may indicate a considerable contribution of a food source derived from terrigenous organic matter, which has low δ34S values close to 0‰, and the bivalve has been reported to have cellulase and hemicellulase activities. Unique fatty acids (iso 17:0 and anteiso 17:0 acids), both characteristic of sulfate-reducing bacteria, were observed in the salt-free, soft-body parts of the bivalve. The concentration of monounsaturated fatty acids, possibly derived from bacteria, was also high. Trace amounts of a polyunsaturated fatty acid (20:5ω3) specific to dinoflagellates were detected. In Corbicula habitats, reductive sandy layers with ample sulfides that were sporadically intercalated into the oxidative sandy sediment were often observed. The stable isotopic signatures of sediment sulfides (acid-volatile sulfide) and associated pore-water sulfates were-8.9 to+8.6‰ and+22.4 to+26.3‰, respectively, indicating the existence of bacterial sulfate-reducing activity and thiobios biomass. These isotopic signatures of the sediment, with the fatty acid composition of the bivalve, confirm the importance of a food source derived from bacteria belonging to the thiobios in the substrate sediments via pedal feeding, rather than direct digestion of terrigenous organic matter, in this estuarine ecosystem.
KW - Biomarkers
KW - Corbicula japonica
KW - Fatty acids
KW - Food resources
KW - Kitakami River, northeastern Japan
KW - Sulfur isotopes
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U2 - 10.1016/j.ecss.2013.04.011
DO - 10.1016/j.ecss.2013.04.011
M3 - Article
AN - SCOPUS:84878381867
SN - 0272-7714
VL - 126
SP - 87
EP - 92
JO - Estuarine, Coastal and Shelf Science
JF - Estuarine, Coastal and Shelf Science
ER -
