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MEPS 216:119-127 (2001)
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Abstract
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Exploitation of a chemosynthetic food resource by the polychaete Capitella sp. I
Hiroaki Tsutsumi1,*, Sam Wainright2, Shigeru Montani3, Megumi Saga1, Sagiri Ichihara1, Kazuhiro Kogure4
1Faculty of Environmental and Symbiotic Sciences, Prefectural University of Kumamoto, 3-1-100 Tsukide, Kumamoto 862, Japan
2US Coast Guard Academy, 15 Mohegan Avenue, New London, Connecticut 06320-8100, USA
3Faculty of Agriculture, Kagawa University, Ikedo, Kida-gun, Kagawa-ken 761-07, Japan
4Ocean Research Institute, Tokyo University, 1-15-1 Minamidai, Shinjuku-ku, Tokyo 164, Japan
*E-mail: hiro@pu-kumamoto.ac.jp
ABSTRACT: In organically enriched sediments of coastal areas, sulfate-reducing bacteria decompose organic matter anaerobically, producing high levels of hydrogen sulfide. Chemoautotrophic sulfur-oxidizing bacteria proliferate at the sulfide/oxygen
interface and use hydrogen sulfide as an electron donor. A few species of small polychaete worms, including Capitella sp. I, often dominate the macrofaunal benthic communities in such sulfide-rich environments in the organically enriched sediments.
In this study, we conducted 2 laboratory experiments to determine whether Capitella sp. I can benefit trophically through the exploitation of the organic matter chemosynthetically produced by sulfur-oxidizing bacteria. In the first experiment, we
reared juveniles of Capitella sp. I with natural sediment of very low organic content, with no additional organic matter, under dark conditions, and exposed them to 3 different levels of sodium sulfide. The worms reared in the sulfide treatments
showed better survival, enhanced growth and reproduction. They had lower d13C values (-24.3[per thou], mean) than control worms (-20.1[per thou], mean) and the sediments in which the worms were cultured (-21.4[per thou], mean). The distinctive
d13C signature of the worms in the sulfide treatments indicates that they did not share the same carbon source as the control worms. The second experiment was done in the same manner as the first, but the carbonate in
the water was replaced with 13CO2 in order to trace the autotrophic fixation of carbon dioxide by chemosynthetic bacteria occurring within the sediments. The results indicate that fixation of 13CO2 was promoted
in sediments with Na2S amendments, and further enhanced by the presence of Capitella sp. I. The worms in these sediments had extremely high d13C values (+5218.2[per thou]). The results of this study
introduce the possibility of enhanced survival and growth of Capitella sp. I in sulfide-rich environments in the organically enriched sediments, facilitated by its utilization of a novel source of organic matter.
KEY WORDS: Capitella · Chemoautotrophic bacteria · Stable isotope · Organic enrichment · 13C · 15N
Full text in pdf format
Published in MEPS Vol.
216
(2001) on July 6
Print ISSN: 0171-8630; Online ISSN: 1616-1599.
Copyright © Inter-Research, Oldendorf/Luhe, 2001
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