ABSTRACT: Phytoplankton bloom events result in distinct changes in the composition and availability of nutrients as well as physical conditions within aquatic ecosystems, resulting in significant effects on bacterial communities. Using a metabarcoding approach, this study investigated the effect of a harmful algal bloom (HAB) of Heterosigma akashiwo in the Sundays Estuary, South Africa, on bacterial community structures in this estuarine ecosystem over an entire bloom event. The occurrence of bacterial lineages occurring in both the oxygen-rich surface water and hypoxic bottom waters in this study reflects the respiratory flexibility and potential for both aerobic and anaerobic metabolism across a wide range of bacterial phylogenetic lineages. A close correlation between the bacterial community profiles and the physiological state of the bloom was observed, with Flavobacteria found in increased relative abundances during the H. akashiwo HAB. Flavobacteria are commonly reported in the literature associated with algal blooms, which is indicative of their central role in the degradation of algal-derived organic matter. Halieaceae were prevalent during the bloom, whilst Synechococcales, Cryomorphaceae and Sporichthyaceae were found to be positively correlated with the decay of the H. akashiwo bloom. Rhodobacteraceae correlated significantly with the H. akashiwo bloom; however, unlike the Rhodobacteraceae specific bloom-associated genera reported in literature (predominantly Roseobacter), up to 74% of the Rhodobacteraceae sequence reads in this study were assigned to the genus Litorimicrobium. The distinct bacterial community profiles recorded throughout the H. akashiwo HAB can be attributed to the influence of the bloom-forming species as well as under-representation of estuarine-occurring HABs in the literature.

中文翻译：

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Heterosigma akashiwo藻类有害繁殖期间的细菌群落动态

摘要：浮游植物开花事件导致水生生态系统中营养物的组成和可用性以及物理条件发生明显变化，从而对细菌群落产生重大影响。使用metabarcoding方法，这项研究调查了有害藻华（HAB）的影响赤潮异弯藻在南非的周日河口，在整个开花过程中研究了该河口生态系统中的细菌群落结构。在这项研究中，在富氧地表水和低氧性底水中都发生了细菌谱系，这反映了广泛的细菌系统发育谱系的呼吸灵活性以及有氧和无氧代谢的潜力。观察到细菌群落特征与水华的生理状态之间存在密切的相关性，其中黄杆菌在H. akashiwo HAB期间相对丰度增加。黄杆菌属在与藻华有关的文献中通常报道了它们的存在，这表明它们在藻源性有机物的降解中起着重要作用。Halieaceae布隆期间普遍，而Synechococcales，Cryomorphaceae和Sporichthyaceae被发现与所述的衰减正相关H.弯藻开花。红景天科与赤潮H.bloom显着相关。然而，不同于Rhodobacteraceae特定开花相关属在文献中报道（主要Roseobacter），上升到74％Rhodobacteraceae在这项研究中的序列读数被分配给Litorimicrobium属。在整个akashiwo HAB中记录到的独特的细菌群落特征可归因于形成花的物种的影响以及文献中出现河口的HAB的代表性不足。