利用環境DNA高通量複合分子條碼技術以探究臺灣東部及西部外海魚類群聚在空間和季節上之差異

Abstract

前人研究顯示，臺灣海域海洋生物的空間與季節性分佈之波動，主要受到其周圍三大水團的匯聚以及季風變化的影響。然而，針對海洋魚類群聚模式的研究大多侷限於稚魚的研究，這在一定程度上是由於採樣的限制。為了解決這一問題，本研究運用環境DNA高通量複合分子條碼技術，克服傳統方法的侷限，對臺灣的海洋魚類多樣性以多尺度的方式進行全面的評估，並進一步探討驅動時空變動的潛在環境因素。本研究於2023年成功完成了為期一年的季節性採樣，其範圍涵蓋了臺灣周圍的24個離岸採樣點。基於先前的研究結果，本分析將臺灣劃分為西部和東部兩個地理區域進行研究。91個採集樣本的分析共偵測到1,026種海洋魚類，包含了從小型底棲和中上水層魚類到大型掠食性大洋性魚類的多樣物種。透過基於距離的冗餘分析檢測到群聚組成在空間上和季節性的顯著差異，此結果推測是受各自區域獨特的海洋條件所影響。在西部海域，北部群聚在組成上呈現出明顯的季節性變化，反映了溫暖的南海表層水團和低溫的中國沿岸水團之間的交替主導，而南部群聚在組成上的變化較小，顯示其全年受到溫暖南海表層水團和黑潮分支水團的持續影響。在東部海域，魚類群聚組成之季節性變化受到黑潮動態的驅動。值得注意的是，在北部採樣點觀察到一個獨特的模式，這可能是由於黑潮撞擊大陸棚引發的湧升流所帶來的環境效應所致。本研究結果為臺灣海域在時空上，由不同的海洋現象影響下形成的海洋魚類多樣性模式提供了新的見解，對未來針對有效管理海洋生態系統的長期調查提供了寶貴的資料。

Earlier studies have shown that the spatial and seasonal distribution and fluctuations of marine organisms in Taiwan are primarily influenced by the three water masses converging in its surrounding areas, as well as by monsoon dynamics. However, research on the patterns of marine fish communities has largely been limited to the studies of larval fishes, partly due to sampling constraints. To address this gap, this study employs environmental DNA (eDNA) metabarcoding to comprehensively assess fish diversity at various scales in Taiwan, aiming to overcome the limitations of conventional methods and further identify the potential environmental factors driving spatiotemporal variations. Throughout this study, a year-long seasonal sampling was successfully conducted across 24 offshore sites around Taiwan in 2023. Based on previous findings, the analysis delineates two geographic regions of Taiwan—the West and the East—for the investigation. Through the analyses of 91 collected samples, a total of 1,026 marine fish taxa are detected, representing a diverse range of species from small benthic and pelagic fish to large predatory oceanic species. Significant spatial and seasonal differences in the community composition are detected, influenced by distinct oceanographic conditions in each region as revealed by distance-based redundancy analysis. In the West, the northern communities exhibited clear seasonal shifts between the dominance of warm South China Sea Surface Water and cold China Coastal Water, while southern communities showed less variation, reflecting the year-round influence of warm South China Sea Surface Water and Kuroshio Branch Water. In the East, seasonal changes in fish community composition are driven by the dynamics of Kuroshio Current. It is noteworthy that a unique pattern was observed at the northern sampling sites, which may be attributed to the environmental effects caused by upwelling triggered by the Kuroshio Current colliding with the continental shelf. These findings provide new insights into the patterns of marine fish diversity in the Taiwan’s waters, shaped by various oceanographic processes over time and space, offering valuable information for future long-term surveys aimed at effective marine ecosystem management.