Benthic foraminifera as trophic links between phytodetritus and benthic metazoans: carbon and nitrogen isotopic evidence
Benthic foraminifera as trophic links between phytodetritus and benthic metazoans: carbon and nitrogen isotopic evidence
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DOI：
10.3354/meps07309
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发表时间：
2008-04
影响因子：
2.5
通讯作者：
H. Nomaki;N. Ogawa;N. Ohkouchi;Hisami Suga;T. Toyofuku;M. Shimanaga;T. Nakatsuka;H. Kitazato
中科院分区：
文献类型：
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作者：
H. Nomaki;N. Ogawa;N. Ohkouchi;Hisami Suga;T. Toyofuku;M. Shimanaga;T. Nakatsuka;H. Kitazato
基于软组织稳定碳氮同位素组成，研究了深海底栖有孔虫和后生动物的营养水平，以评价有孔虫在深海底栖生态系统中的作用。本研究于2004年4月、2004年11月及2005年8月三次在日本相模湾的两个深海地点（水深750及1430米）采集活底栖有孔虫及后生动物。碳和氮同位素组成在分析的有孔虫物种之间存在显著差异。深层底栖有孔虫的δ 15 N值在6.7 ~ 11.0‰之间（典型值为7 ~ 10‰），种间差异较大。这表明大多数底栖有孔虫主要利用表层沉积物（4.5‰）或颗粒有机物质（6.4‰）作为食物来源。许多后生动物的小底栖生物，特别是小动物大小的多毛类、一些羽足类桡足类和kinorhynchs（仅在较浅的部位检测），其δ 15 N比有孔虫重，表明它们比底栖有孔虫具有更高的营养水平。大型和巨型底栖动物（蛛形、蛇形和齿形）的δ 15 N值为10 ~ 14‰，比后生小底栖动物和底栖有孔虫高1 ~ 2级。在较浅的地点也观察到类似的同位素趋势。结合同位素证据和对一些后生减数生底栖动物肠道内容物的观察，结合以往的实验结果，相模湾深海底栖有孔虫被认为是植物碎屑和沉积物向后生动物能量流动的桥梁。
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 dif- fered among the analysed foraminiferal species. At the deeper site δ 15 N 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 mat- ter (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 δ 15 N heavier than foraminifera, suggesting that they occupy higher trophic levels than benthic foraminifera. Macro- and megabenthos (spatangoids, ophiuroids and Dentalioida) exhibited δ 15 N 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 meio- benthos, 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.