Department of Molecular Sciences, Macquarie University, Sydney, NSW, Australia.
School of Science and Health, Western Sydney University, Penrith, NSW, Australia.
PLoS One. 2018 Dec 26;13(12):e0209857. doi: 10.1371/journal.pone.0209857. eCollection 2018.
Sydney Harbour is subjected to persistent stress associated with anthropogenic activity and global climate change, but is particularly subjected to pulse stress events associated with stormwater input during episodic periods of high rainfall. Photosynthetic microbes underpin metazoan diversity within estuarine systems and are therefore important bioindicators of ecosystem health; yet how stormwater input affects their occurrence and distribution in Sydney Harbour remains poorly understood. We utilised molecular tools (16S/18S rRNA and petB genes) to examine how the phytoplankton community structure (both prokaryotes and eukaryotes) within Sydney Harbour varies between high and low rainfall periods. The relative proportion of phytoplankton sequences was more abundant during the high rainfall period, comprising mainly of diatoms, an important functional group supporting increased productivity within estuarine systems, together with cyanobacteria. Increased spatial variability in the phytoplankton community composition was observed, potentially driven by the steepened physico-chemical gradients associated with stormwater inflow. Conversely, during a low rainfall period, the proportion of planktonic photosynthetic microbes was significantly lower and the persistent phytoplankton were predominantly represented by chlorophyte and dinoflagellate sequences, with lower overall diversity. Differences in phytoplankton composition between the high and low rainfall periods were correlated with temperature, salinity, total nitrogen and silicate. These results suggest that increased frequency of high-rainfall events may change the composition, productivity and health of the estuary. Our study begins to populate the knowledge gap in the phytoplankton community structure and substantial changes associated with transient environmental perturbations, an essential step towards unravelling the dynamics of primary production in a highly urbanised estuarine ecosystem in response to climate change and other anthropogenic stressors.
悉尼港受到与人为活动和全球气候变化相关的持续压力，但特别容易受到与 episodic 期高降雨量期间雨水输入相关的脉冲压力事件的影响。光合作用微生物是河口系统后生动物多样性的基础，因此是生态系统健康的重要生物指标；然而，雨水输入如何影响它们在悉尼港的发生和分布仍知之甚少。我们利用分子工具（16S/18S rRNA 和 petB 基因）来研究悉尼港浮游植物群落结构（原核生物和真核生物）在高降雨期和低降雨期之间的变化。浮游植物序列的相对比例在高降雨期更为丰富，主要由硅藻组成，硅藻是支持河口系统生产力增加的重要功能组，以及蓝藻。观察到浮游植物群落组成的空间变异性增加，这可能是由与雨水流入相关的物理化学梯度变陡驱动的。相反，在低降雨期，浮游光合作用微生物的比例显著降低，持久的浮游植物主要由绿藻和甲藻序列组成，整体多样性较低。高降雨期和低降雨期之间浮游植物组成的差异与温度、盐度、总氮和硅酸盐有关。这些结果表明，高降雨量事件的频率增加可能会改变河口的组成、生产力和健康状况。我们的研究开始填补浮游植物群落结构和与瞬态环境干扰相关的重大变化方面的知识空白，这是揭示高度城市化河口生态系统对气候变化和其他人为胁迫的初级生产力动态的重要一步。
