The Xiamen Symposium on Marine Environmental Sciences (XMAS 2025)

Zooplankton plays a crucial role in coral ecosystems, serving as vital indicators of environmental change and biodiversity maintenance. However, the limitation of the low spatial and temporal resolution and the difficulty of reproducing the natural state of organisms by conventional trawling methods, hindered our in-depth knowledge of the zooplankton community dynamics and its response to environmental changes. In this study, we utilized the Imaging Plankton Probe, an in situ microscopic imaging system, to conduct high-frequency observations over six months within a coral ecosystem in the coastal East China Sea, providing continuous datasets that address longstanding questions about planktonic ecosystem dynamics. We captured biological images using in situ high-frequency acquisition techniques and categorized approximately 860,000 biological images using a machine-learning-based approach (EfficientNet), and found that dominant zooplankton taxa, such as copepods and amphipods, showed a diurnal pattern of abundance variation with increases in nighttime and decreases in daytime. Moreover, the effects of two key factors—tides and the daylight cycle—on the daily variation of zooplankton through high-frequency datasets of irregular semidiurnal tides. Results show that the probability of zooplankton detection was higher during low tide compared to high tide, suggesting that zooplankton abundance is greater at low tide. Furthermore, a positive correlation between tidal strength and zooplankton abundance was detected. Here, we present a promising neritic observing system that reveals the tidal and photoperiodic dynamics of zooplankton groups in a coral ecosystem. Our methods and findings pave the way for further understanding neritic plankton biodiversity and have implications for coral ecosystem conservation strategies.

zooplankton, in situ image, imaging plankton probe, tide, diel variation