It has been proposed that, within flood-pulse systems, seasonally dynamic conditions promote extremely high levels of biodiversity. In this paper, we aim to understand how variation in environmental conditions and habitat availability, across space and time, influences the structure and composition of plankton diatom communities within the Tonle-Sap Lake (Cambodia) during two flood-pulse cycles. We hypothesize that (i) communities vary considerably across space and time, (ii) environmental filtering accounts for a substantial portion of the variation in community composition, and (iii) shifts in meta-community structure occur seasonally, due to variation in both environmental conditions and habitat availability. A principal component analysis and a permutational multivariate analysis of variance were used to characterize spatio-temporal variations in environmental conditions, community structure and composition. Determinants of community variations across space were identified by redundancy analyses and variation partitioning, while seasonal changes in meta-community structure were assessed by investigating temporal changes in β-diversity. Our results indicate that (i) spatial variations in community structure and composition are largely influenced by the seasonal flood-pulse, (ii) environmental filtering is the most likely process driving the compositional changes, and (iii) changes in diatom life-form community provide insights into the hydrological functioning of the Tonle Sap. We conclude that the survey of diatom communities may constitute a relevant sensor of hydrological change in the system and could be used to derive regionally specific hypotheses about how global climate change is impacting the lake’s functioning.

中文翻译：

---

热带洪水脉冲湖中的浮游硅藻群落动态：洞里萨湖（柬埔寨）

有人提出，在洪水脉冲系统中，季节性动态条件促进了极高水平的生物多样性。在本文中，我们旨在了解环境条件和栖息地可用性的变化如何在两个洪水脉冲周期期间影响洞里萨湖（柬埔寨）内的浮游生物硅藻群落的结构和组成。我们假设 (i) 社区在空间和时间上有很大差异，(ii) 环境过滤占社区组成变化的很大一部分，以及 (iii) 元社区结构的变化季节性发生，由于环境和时间的变化条件和栖息地可用性。使用主成分分析和方差的置换多元分析来表征环境条件、群落结构和组成的时空变化。通过冗余分析和变异划分确定了跨空间群落变异的决定因素，而通过调查β多样性的时间变化来评估元群落结构的季节性变化。我们的结果表明（i）群落结构和组成的空间变化在很大程度上受季节性洪水脉冲的影响，（ii）环境过滤是最有可能驱动组成变化的过程，以及（iii）硅藻生命形式群落的变化深入了解洞里萨湖的水文功能。