Liu Bingqing, Chen Mianrun, Wang Chunsheng
School of Oceanography, Shanghai Jiao Tong University, Shanghai 200030, China.
South China Sea Institute of Planning and Environmental Research/Nansha Islands Coral Reef Ecosystem National Observation and Research Station, State Oceanic Administration, Guangzhou 510300, China.
Microorganisms. 2024 Sep 30;12(10):1982. doi: 10.3390/microorganisms12101982.
Daya Bay, a semi-enclosed bay in the northern South China Sea and to the east of the Pearl River Estuary, is rich in biological resources and diverse habitats. Current research on mesozooplankton in Daya Bay has mainly focused on aspects such as species composition, biomass, and biodiversity in the zooplankton community. However, there is limited research on the top-down effects of mesozooplankton on prey communities. This study conducted seasonal in-situ cultivation experiments from 2015 to 2017. By combining mesozooplankton grazing experiments and microzooplankton dilution experiments, the mesozooplankton clearance rate and trophic cascading effect on low trophic levels were calculated. Results showed evident mesozooplankton selective feeding behavior and corresponding trophic cascades with seasonal variations, these being significantly higher in the spring and summer and lower in the autumn and winter. Different sizes of phytoplankton showed significant differences; large-sized phytoplankton received high feeding rates but low trophic cascades by mesozooplankton, while the opposite was true for small-sized phytoplankton. Trophic cascades contribute in three ways: offsetting direct grazing mortality, changing prey community structure via its effects on different phytoplankton sizes, and reducing ciliate grazing impacts at an average of 14.4 ± 7.8%, maintaining around 70% ciliate grazing impacts in nature. The composition of mesozooplankton was the primary reason for explaining feeding preferences, including size selectivity and omnivory. For instance, high cladoceran abundance caused high feeding rates while, on the other hand, high omnivorous copepods abundance caused high trophic cascades on small-sized phytoplankton. General additive model (GAM) analysis revealed that the changes in trophic cascades were highly dependent on temperature, ciliate abundance, mesozooplankton feeding rates on ciliates, and ciliate feeding rates on phytoplankton. The significance of this study lies in its contribution to providing valuable insights into the role of mesozooplankton in the marine food web and their impact on lower trophic levels. In addition, the findings can help inform the management and conservation of marine ecosystems, as well as guide future research in this field.
大亚湾是南海北部、珠江口以东的一个半封闭海湾，生物资源丰富，栖息地多样。目前对大亚湾中型浮游动物的研究主要集中在浮游动物群落的物种组成、生物量和生物多样性等方面。然而，关于中型浮游动物对猎物群落的自上而下的影响的研究却很有限。本研究在2015年至2017年进行了季节性原位培养实验。通过结合中型浮游动物摄食实验和微型浮游动物稀释实验，计算了中型浮游动物的清除率和对低营养级的营养级联效应。结果表明，中型浮游动物具有明显的选择性摄食行为和相应的营养级联效应，且随季节变化，春季和夏季显著高于秋季和冬季。不同大小的浮游植物表现出显著差异；大型浮游植物被中型浮游动物的摄食率高，但营养级联效应低，而小型浮游植物则相反。营养级联效应通过三种方式发挥作用：抵消直接摄食死亡率，通过对不同大小浮游植物的影响改变猎物群落结构，以及平均降低14.4±7.8%的纤毛虫摄食影响，在自然状态下保持约70%的纤毛虫摄食影响。中型浮游动物的组成是解释摄食偏好的主要原因，包括大小选择性和杂食性。例如，高枝角类丰度导致高摄食率，而另一方面高杂食性桡足类丰度导致对小型浮游植物的高营养级联效应。广义相加模型（GAM）分析表明，营养级联效应的变化高度依赖于温度、纤毛虫丰度、中型浮游动物对纤毛虫的摄食率以及纤毛虫对浮游植物的摄食率。本研究的意义在于为深入了解中型浮游动物在海洋食物网中的作用及其对低营养级的影响提供了有价值的见解。此外，研究结果有助于为海洋生态系统的管理和保护提供信息，并指导该领域的未来研究。
