Benthic foraminifera as trophic links between phytodetritus and benthic metazoans: carbon and nitrogen isotopic evidence

Abstract

MEPS Marine Ecology Progress Series Contact the journal Facebook Twitter RSS Mailing List Subscribe to our mailing list via Mailchimp HomeLatest VolumeAbout the JournalEditorsTheme Sections MEPS 357:153-164 (2008) - DOI: https://doi.org/10.3354/meps07309 Benthic foraminifera as trophic links between phytodetritus and benthic metazoans: carbon and nitrogen isotopic evidence Hidetaka Nomaki1,*, Nanako O. Ogawa1, Naohiko Ohkouchi1, Hisami Suga1, Takashi Toyofuku1, Motohiro Shimanaga2, Takeshi Nakatsuka3, Hiroshi Kitazato1 1Institute for Research on Earth Evolution, Japan Agency for Marine-Earth Science and Technology (JAMSTEC), 2–15, Natsushima-cho, Yokosuka City, Kanagawa 237-0061, Japan 2Aitsu Marine Station, Center for Marine Environment Studies, Kumamoto University, 6061 Aitsu, Matsushima-machi, Kamiamakusa-shi, Kumamoto 861-6102, Japan 3Institute of Low Temperature Science, Hokkaido University, Kita-19, Nishi-8, Kita-Ku, Sapporo 060-0819, Japan *Email: nomakih@jamstec.go.jp ABSTRACT: We examined the trophic levels of deep-sea benthic foraminifera and metazoans based on stable carbon and nitrogen isotopic compositions of soft tissue to evaluate the role of foraminifera in deep-sea benthic ecosystems. Living benthic foraminifera and metazoans were collected from 2 bathyal sites in Sagami Bay, Japan (water depths 750 and 1430 m) on 3 occasions (April 2004, November 2004 and August 2005). Both carbon and nitrogen isotopic compositions significantly differed among the analysed foraminiferal species. At the deeper site δ15N of the benthic foraminifera ranged from 6.7 to 11.0‰ (typically 7 to 10‰) with considerable interspecies variations. This implies that most benthic foraminifera utilize primarily surface sediments (4.5‰) or particulate organic matter (6.4‰) as their food sources. Many metazoan meiobenthic organisms, in particular polychaetes of meiofaunal size, some harpacticoid copepods, and kinorhynchs (examined only at the shallower site), exhibited δ15N heavier than foraminifera, suggesting that they occupy higher trophic levels than benthic foraminifera. Macro- and megabenthos (spatangoids, ophiuroids and Dentalioida) exhibited δ15N of 10 to 14‰, suggesting they belong in trophic levels 1 to 2 steps higher than metazoan meiobenthos and benthic foraminifera. Similar isotopic trends were observed at the shallower site. Combining the isotopic evidences and the observations on gut contents of some metazoan meiobenthos, together with previous experimental results, the benthic foraminifera in the bathyal Sagami Bay are considered a bridge in the energy flow from phytodetritus and sediments to metazoans. KEY WORDS: Benthic foraminifera · Metazoan meiobenthos · Carbon isotopic composition · Nitrogen isotopic composition · Trophic level · Deep-sea food web · Foraminiferivory Full text in pdf format Supplementary appendices PreviousNextCite this article as: Nomaki H, Ogawa NO, Ohkouchi N, Suga H and others (2008) Benthic foraminifera as trophic links between phytodetritus and benthic metazoans: carbon and nitrogen isotopic evidence. Mar Ecol Prog Ser 357:153-164. https://doi.org/10.3354/meps07309Export citation RSS - Facebook - Tweet - linkedIn Cited by Published in MEPS Vol. 357. Online publication date: April 07, 2008 Print ISSN: 0171-8630; Online ISSN: 1616-1599 Copyright © 2008 Inter-Research.