東海橈足類群集結構與水文之關係

Abstract

橈足類在海洋食物網中為連結初級生產者與較高階消費者間的能量傳遞者，為保持漁業資源永續性的重要因子。東海地區為重要漁場，因複雜的洋流系統而有多樣的水文環境。統合橈足類群集對於不同水文環境之關係是必要的，進一步可推測群集的形成機制。本研究目標為描述東海地區橈足類物種組成，並探究各水團的橈足類指標物種，假說為東海地區橈足類物種組成會與水團相對應。本研究於2006年夏季及2008年冬季航次收集橈足類樣本及環境變數。以無階層分群法 (nonhierarchical clustering analysis) 觀察測站間物種組成結構之相似性。利用前進特徵選擇法 (forward selection)找出可顯著解釋橈足類群集的環境變數，並以Redundancy analysis探討物種組成與水團的關鍵環境變數之關係。使用指標物種分析探究各水團的橈足類指標物種。本研究在夏、冬季各定義了4個、3個水團。無論夏季或冬季，無階層分群法的第一群中之主要的對應水團為台灣暖水團，第二群對應水團為河口水。且物種群落相似性的界線與水團大致吻合。根據指標物種分析，夏季有9物種為夏季台灣暖水團之指標物種；2物種為夏季第二混合水團之指標物種；1物種為夏季河口水指標物種。冬季有12物種為冬季台灣暖水團指標物種；1物種為冬季混合水團指標物種；2物種為冬季河口水指標物種。本研究指出東海橈足類群集結構分佈與水團相對應，並探究出各水團的指標物種。

Copepods link primary producers with organisms of higher trophic levels in marine food webs, and are crucial for sustainability of fisheries. The East China Sea (ECS) is an important fishery ground having diverse hydrographic conditions with complex circulation. It is necessary to understand the relationship between copepod communities and hydrographic conditions, and investigate the mechanisms shaping the community structures. This study aimed to describe the composition of copepods assemblages in the ECS, and explored the indicator species of water masses. We hypothesized that the copepod community structures correspond with water masses. Copepods composition and environmental data were collected from two cruises during June 2006 and January 2008 in the ECS. We defined water masses by T-S diagrams. The similarity of copepod communities among stations was explored by nonhierarchical clustering analysis (NHC). Redundancy analysis (RDA) through the forward selection procedure was used to investigate variance of copepods composition with important environmental factors of water masses. The indicator species analysis (IndVal) was applied to extract the indicator species of each water mass. We defined four and three water masses in the summer and winter cruises, respectively. During summer, community structures of the first NHC cluster corresponded with the water mass of the Taiwan Warm Current (TWC.s); while the second cluster was coincident with the Estuary (E.s). The first and second NHC clusters of community structures in the winter cruise corresponded with the TWC.w, and E.w, respectively. According to the indicator species analysis in summer, 9 species were the indicator species for the TWC.s, 2 species for the Mix.s2, and one species for the E.s. During winter, 12 species were the indicator species for the TWC.w, 2 species for the E.w, and only one species for the Mix.w. In this study, our results indicated obvious water mass-specific indication within copepods communities, and recognized the indicator species of specific water mass in the ECS.