颱風效應對東海南部細菌群落之影響

Abstract

海洋細菌浮游生物在海洋生態系統中扮演著重要角色。然而，儘管颱風的強度和頻率預計會由於氣候變遷而增加，颱風對海洋細菌群落的影響尚未被深入研究。本研究在2018年7月超級颱風瑪麗亞襲擊中國東海南部期間，進行了颱風前後的取樣工作，旨在對比（i）颱風前後的環境條件和（ii）颱風前後的海洋細菌群落。考慮到優勢(dominant taxa)和稀有(rare taxa)海洋細菌群落可能對颱風干擾表現出不同的反應，本研究分別檢驗了這兩種細菌群體。颱風前後，共計在8個站點進行了細菌群落和環境因子的收集，每個站點包含4個採樣深度，包括表層（SUR）、葉綠素最大層（DCM）、DCM和底部之間的中間深度（MID）以及底層（BOT）。本研究使用高通量測序技術獲取了細菌的群落組成。幾個物理化學因子，包括溫度、溶氧飽和度、螢光值和無機氮（DIN），在颱風前後顯示出顯著差異。物種多樣性指數（包括豐富度、均勻度和香農多樣性指數）在颱風前後未顯示出顯著差異。然而，就組成而言，整體(dominant taxa + rare taxa)和稀少(rare taxa)物種的細菌群落在颱風前後顯示出顯著差異(p<0.05)，但優勢物種(dominant taxa)的細菌群落則僅達統計顯著標準邊緣(p=0.072)。此外，在上層(SUR和DCM)水體存在著環境差異與群落差異之間的正相關，但在下層(MID和BOT)水體則沒有這種關聯。再者，dbRDA雙變量圖顯示，受颱風事件影響，溫度、鹽度和螢光值可能對中國東海南部的細菌群落產生影響。

Marine bacterioplankton play an important role in the marine ecosystem. Typhoon effects on marine bacterioplankton community are yet to be investigated, albeit that intensity and frequency of typhoons are expected to increase due to climate change. With sampling on board of the research vessel before and after the super typhoon Maria in July 2018 in the southern East China Sea (ECS), the aim of this study is to contrast (i) the environmental conditions and (ii) the bacterioplankton communities before and after the typhoon. This study examined separately for both dominant and rare bacterioplankton, considering that these two groups of bacteria may exhibit different responses to the typhoon disturbance. Bacterioplankton communities along with environmental variables were collected at a total of 8 stations before and after the typhoon, with each station containing 4 sampling depths, including surface (SUR), depth of chlorophyll maximum (DCM), a middle depth between DCM and bottom (MID), and the layer close to the bottom (BOT). This study employed high-throughput sequencing techniques to obtain the community of bacterioplankton. Several physicochemical variables, including temperature, dissolved-oxygen saturation, fluorescence, and DIN, changed significantly pre- and post-typhoon. Species diversity indices (including Richness, Evenness, and Shannon index) showed no significant difference after the typhoon. Whereas for the taxonomic composition, the communities of whole (dominant + rare) taxa and rare taxa were significantly different pre- and post-typhoon (p<0.05), yet the dominant taxa were only marginally significant (p=0.072). In addition, a positive correlation between physicochemical dissimilarity versus community dissimilarity exists in the upper layers (SUR and DCM), but not in the lower layers (MID and BOT). Furthermore, dbRDA biplot indicates that temperature, salinity, and fluorescence explained the bacterial community variation in the southern ESC, which might be influenced by the typhoon.