The Guangxi Key Laboratory of Beibu Gulf Marine Biodiversity Conservation, College of Marine Sciences, Beibu Gulf University, Qinzhou, 535011, China.
BMC Ecol Evol. 2024 Oct 22;24(1):129. doi: 10.1186/s12862-024-02315-1.
Sanniang Bay (SNB) and Dafeng River (DFR), located in the northern Beibu Gulf, is well-known as one of the eight habitats for humpback dolphins in China. This region is representative of typical estuarine and bay ecosystems and produce complex hydrodynamic seawater conditions. Moreover, anthropogenic pressure, such as eutrophication and large-scale infrastructure projects, have caused ongoing habitat deterioration and loss. It is urgent to know the phytoplankton community and their relationships with environmental factors in this region.
In this study, we assessed the diversity and assembly mechanisms of phytoplankton communities, as well as their relationship with the physicochemical characteristics of seawater in SNB and DFR region using 18 S rDNA metabarcoding analysis. The results showed that seasonal changes markedly impacted the alpha diversity of the phytoplankton community. From March to July, with the average temperature increasing from 25.2℃ to 28.1℃,the Shannon or Species Richness were negatively correlated with temperature. During hot season (in Sep, average temperature 32.1℃), phytoplankton diversity was negatively correlated with nutrients (NH, NO, PO, TN). Additionally, during the rainy season, the Bray-Curtis similarity of the phytoplankton community was significantly lower than during the dry season. In March, the distance among the sampling sites was most strongly and positively correlated with the Bray-Curtis dissimilarity. Stochastic processes, specifically dispersal limitation and ecological drift, are the primary drivers of community assembly, while deterministic assembly processes (mainly heterogeneous selection) contribute a relatively minor portion (< 17%).
Rising temperature diminished the diversity of phytoplankton in SNB and DFR, and nutrient inputs and eutrophication in estuarine areas will aggravate the loss of phytoplankton diversity.
三埯湾（SNB）和大风江（DFR）位于北部湾北部，是中国著名的八大中华白海豚栖息地之一。该地区是典型的河口和海湾生态系统的代表，产生复杂的水动力海水条件。此外，人为压力，如富营养化和大规模基础设施项目，导致栖息地持续恶化和丧失。迫切需要了解该地区浮游植物群落及其与环境因素的关系。
本研究采用 18S rDNA 宏条形码分析，评估了 SNB 和 DFR 地区浮游植物群落的多样性和组装机制及其与海水理化特性的关系。结果表明，季节变化明显影响浮游植物群落的α多样性。从 3 月到 7 月，平均温度从 25.2℃增加到 28.1℃，香农或物种丰富度与温度呈负相关。在炎热季节（9 月，平均温度 32.1℃），浮游植物多样性与营养物质（NH、NO、PO、TN）呈负相关。此外，在雨季，浮游植物群落的 Bray-Curtis 相似性显著低于旱季。3 月，采样点之间的距离与 Bray-Curtis 不相似性呈最强正相关。扩散限制和生态漂移等随机过程是群落组装的主要驱动因素，而确定性组装过程（主要是异质选择）的贡献相对较小（<17%）。
温度升高降低了 SNB 和 DFR 浮游植物的多样性，而河口地区的营养物质输入和富营养化将加剧浮游植物多样性的丧失。
