流清河湾浮游生物群落对河口环境变化的不同响应及其关键驱动因素

Differential responses of the plankton community to environmental changes in the estuary of the flowing Qinghe BayWeng Chenshi1,2,3, Li Zhixiang2,3, Wang Yingzhe1,2,3, DING Dongsheng2,3, CUI Zhengguo2,3, QU Keming2,3, Hu Haiyan1, WEI Yuqiu2,3①

中文关键词: 流清河湾  浮游生物群落  环境变化  赤潮  温度  气象灾害  

英文关键词: Liuqinghe bays  Plankton communities  Environmental change  Red tide  Temperature  Meteorological hazards  

中文摘要:

      河流和海洋环境之间存在着紧密的交互关系,因此河口生态系统在生物多样性过程中扮演着重要角色。浮游植物和浮游动物已经被证实可以作为河口生态系统水质状况的生物指标。因此,综合评价多重环境因素对河口生态系统中浮游植物和浮游动物群落的影响至关重要。目前,关于流清河湾浮游生物群落及环境因子影响的研究相对空白,因此我们于2021年3月(春季)、8月(夏季)和10月(秋季)采集了流清河湾海域7个站位的水样,获得了生物数据(即浮游植物和浮游动物)及环境因子数据。研究结果表明,3个航次共鉴定出浮游植物3门94种,以硅藻为主,丰度及碳生物量在夏季达到最大值(242.50 ± 136.40 × 103 cells/m3; 946.89 ± 810.66 μg C/m3)；浮游动物共10类48种,桡足类出现次数最多,但春季最优势浮游动物为浮游幼虫夜光虫(Noctiluca miliaris),且丰度及生物量在春季最大(5665.71 ± 4576.32 (ind/m3; 431.55 ± 298.80 mg/m3)。通过冗余分析(RDA)和Pearson相关性分析探究了环境因子对浮游生物优势种和组成的影响。结果表明,流清河湾浮游生物存在显著的时空变化,其中春夏季浮游生物优势种的主要影响因素是温度和营养盐浓度；影响秋季浮游生物优势种的主要驱动力是温度、盐度及营养盐,并且春秋季存在发生赤潮的潜力。此外,洋流、陆地径流及气象灾害等也是影响浮游生物优势种群落组成的重要因素。本研究的结果有利于提高对河口生态系统浮游生物群落的了解,为科学管理流清河湾生态环境和深入了解海湾浮游生物群落变化的机制提供理论基础。

英文摘要:

      Estuarine ecosystems play an important role in biodiversity processes because of the close interrelationships between riverine and marine environments. Phytoplankton and zooplankton have been shown to serve as ecological indicators of water quality status in estuarine ecosystems. Therefore, an integrated evaluation of the effects of multiple environmental factors on phytoplankton and zooplankton communities in estuarine ecosystems is essential. Previous studies have often been limited to the interaction between a single phytoplankton or zooplankton and environmental factors, while studies on the mechanism of the overall planktonic response to environmental factors have been lacking. Therefore, we collected water samples from seven stations in the waters of Liuqinghe River Bay in March (spring), August (summer) and October (fall) 2021, respectively. Redundancy analysis (RDA) and Pearson correlation analysis were used to explore the effects of environmental factors on phytoplankton and zooplankton dominant species and communities. The results showed that there were large seasonal differences in water temperature in the study area, with the highest water temperature (23.70 ± 0.17 °C) in summer and the lowest water temperature (5.91 ± 0.03 °C) in spring; changes in the mean salinity of offshore estuarine waters (with variations ranging from 30.29 to 31.70) were usually caused by inputs from estuarine runoff, showing obvious seasonal characteristics, and salinity among different stations did not significant differences; pH decreased with increasing water temperature. Compared with the first three hydrological parameters, chemical oxygen demand (COD), Chl a and nutrient salts did not show obvious seasonal patterns. In 2021, 94 species of phytoplankton from 3 phyla were identified during the 3 cruises, with 80 species of Bacillariophyta being the most abundant, followed by 13 species of Pyrrophyta and 1 species of Chrysophyta, and it is worth mentioning that the same species of Chrysophyta was identified in all the 3 cruises. The spring cruise in 2021 identified a total of 44 species from 3 phyla; the summer cruise had the richest community composition with 58 species from 3 phyla; and the fall cruise identified 55 species from 3 phyla. In addition, the mean abundance of phytoplankton in Liuqinghe River Bay in 2021 reached its maximum in summer (242.50 ± 136.40 × 103 cells/m3 ), and the mean abundance in spring (19.38 ± 12.23 cells/m3 ) was at the lowest level. Whereas, the seasonal variation of mean phytoplankton biomass in 2021 in Liuching River Bay showed the same trend with abundance, with maximum carbon biomass (946.89 ± 810.66 μg C/m3) in summer and the lowest level of carbon biomass (31.15 ± 20.96 μg C/m3) in spring. A total of 48 species of zooplankton were identified in 10 groups, with copepods being the most numerous (15 species), followed by pelagic larvae and hydroidomedusa (11 species each), tunicate (3 species), chaetognaths and cladocera (2 species each), and one species of jellyfish, amphipoda, mysidacea and euphausia. A total of 14 species of zooplankton from five taxa were identified during the spring cruise; 28 species from seven taxa were identified during the summer cruise; and 25 species from eight taxa were identified during the fall cruise. Copepods and pelagic larvae had the highest frequency of occurrence in the samples from each seasonal cruise, but the frequency of hydroidomedusa gradually increased over time. Moreover, the mean zooplankton abundance in the study area showed a clear seasonal pattern ranging from 55.00 ± 12.52 ~ 5665.71 ± 4576.32 (ind/m3), with the maximum mean abundance in spring and the minimum mean abundance in fall. Biomass exhibited a similar seasonal pattern to abundance, showing an overall decreasing trend. In 2021, the phytoplankton Shannon-Wiener diversity index (H′) and Pielou’s evenness index (J) in Liuqinghe Bay varied greatly among the three seasons, and there were significant differences among different stations; the average Pielou’s evenness index (J) of phytoplankton did not differ significantly among seasons, especially in spring and summer, but the Pielou’s evenness index (J) fluctuated greatly among different stations. In general, phytoplankton biodiversity was richest in summer and poorest in spring, while the evenness index was relatively evenly distributed in spring and summer and more scattered in fall. The zooplankton Shannon-Wiener diversity index (H′) and Pielou’s evenness index (J) showed very similar trends, with zooplankton Shannon-Wiener diversity index (H′) and Pielou’s evenness index (J) generally higher in summer and fall than in spring, and the fluctuation of Shannon-Wiener diversity index (H′) in summer and fall was also stronger than that in spring. The overall trend was higher in summer than in fall than in spring. Over all, there were significant spatial and temporal variations of plankton in Liuqinghe Bay, in which the main influences on plankton dominant species in spring and summer were temperature and nutrient salt concentration; the main drivers affecting plankton dominant species in fall were temperature, salinity and nutrient salts, and there was a potential for red tides to occur in spring and fall. In addition, ocean currents, land runoff and meteorological hazards are also important factors influencing the community composition of dominant zooplankton species. The results of this study will help to improve the understanding of plankton communities in estuarine ecosystems and provide a theoretical basis for the scientific management of the ecological environment of Liuqinghe Bay and an in-depth understanding of the mechanisms of plankton community changes in the bay.