底棲性有孔蟲群集組成與冷泉生地化環境之關連 - 以臺灣西南海域四方圈合海脊為例

The benthic foraminifera communities in relation to cold seep biogeochemistry – an example from the Four Way Closure Ridge, offshore southwestern Taiwan

蔣孟庭(Meng-Ting Chiang)

指導教授 ： 魏國彥

共同指導教授 ： 林玉詩

國立臺灣大學/理學院/地質科學研究所/碩士(2016年)

https://doi.org/10.6342/NTU201610368

摘要

摘要
底棲性有孔蟲是深海沈積物碳循環中最重要的真核生物之一，然而，其在冷泉生態系中的地位仍在初期研究階段。本研究以數種多變量統計方法探討臺灣西南海域四方圈合海脊冷泉區的底棲性有孔蟲群集結構，以及造成物種組成差異的主要環境因子，並以具備即時影像系統的採樣器在冷泉、過渡區，以及背景環境各採了一根岩芯為研究材料。在表層 1 公分的沈積物中，體型 >250 um 的群集有超過 50% 的膠結質殼體底棲性有孔蟲，可能是因上覆水以及孔隙水中碳酸鹽飽和度偏低所致。冷泉底棲有孔蟲群集的生物多樣性指標在三者中數值最低，過渡區群集與背景群集的數值則十分相近。然而，群集分析顯示過渡區群集與冷泉群群集組成上較相似。指標物種分析結果指出，冷泉的優勢指標物種是膠結質有孔蟲 Haplophramoides bradyi niigataensis，而鈣質有孔蟲 Bulimina aculeata 和 Cassidulinoides differens 則是泛冷泉環境的優勢指標物種。典型相關分析結果顯示，影響底棲性有孔蟲物種組成差異的主要環境因素是孔隙水中的硫酸鹽與溶氧濃度。更多冷泉底棲性有孔蟲生態資訊有賴後續定量研究分析。

關鍵字

底棲性有孔蟲 ； 物種組成 ； 冷泉 ； 四方圈合海脊 ； 指標物種分析 ； 典型相關分析

並列摘要

Abstract
Benthic foraminifera are the most abundant eukaryotes and play an important role in the cycling of organic matter in deep sea environments. However, their ecology in cold seep environments, one of the most unusual seafloor habitats, is just beginning to be revealed. This study employed multiple multivariate statistical approaches to investigate the benthic foraminiferal community composition and the controlling environmental factors in the cold seep region on the Four Way Closure Ridge, offshore SW Taiwan. Sediment cores were retrieved from three sites (seep, transition, and reference) using video-guided sampling equipment. Faunal analysis based on the size class >250 um showed that the three sites shared the same feature of having abundant agglutinated benthic foraminifera (>50%) in the topmost sediment, probably as a result of the low carbonate saturation state in the overlying and pore waters. The cold seep communities had the lowest biodiversity, but cluster analysis indicated substantial similarity in community composition shared between the seep and transition sites. Indicator species analysis suggested Haplophramoides bradyi niigataensis, an agglutinated species, to be the dominant indicator of the seepage hotspot, whereas Bulimina aculeata and Cassidulinoides differens were the dominant indicator species in the broadly defined cold seep region. Canonical correspondence analysis showed that the concentration of sulfate and dissolved oxygen in the pore water were the most significant biogeochemical factors explaining the community variance. The patterns delineated objectively and quantitatively by these numerical ecology tools offered a basic understanding of the benthic foraminiferal ecology in modern cold seeps developed on accretionary wedges.

並列關鍵字

benthic foraminifera ； species composition ； cold seeps ； Four Way Closure Ridge ； indicator species analysis ； canonical correspondence analysis.

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