Abstract: The mangrove-aquaculture coupled system is a sustainable development model that balances mangrove conservation with the development of coastal aquaculture. Understanding the spatiotemporal variation characteristics and environmental drivers of phytoplankton communities is key to recognizing the ecological buffering role of this coupled system. From September 2024 to February 2025, we established eight sampling sites across three habitat types (Mangrove-aquaculture coupled ponds, tidal channels, and traditional aquaculture ponds) within the Taishan Zhenhai Bay Mangrove National Wetland Park in Guangdong Province. By collecting water samples to analyze phytoplankton and related environmental parameters, we examined the species composition, spatial patterns, and relationships with environmental factors. The results showed that, among the 22 samples, a total of 96 species, including undetermined species at the genus level, were identified. Diatoms (64 species) and dinoflagellates (12 species) dominated in terms of species richness, with Thalassiosira sp. being the predominant species. The Shannon-Wiener index generally followed a pattern of tidal channel>coupled ponds>traditional aquaculture ponds (Except in February 2025), while the community robustness index indicated that coupled ponds exhibited the least inter-seasonal fluctuation and the most stable community. Non-metric multidimensional scaling analysis showed that the similarity distance between the phytoplankton communities in the coupled ponds and those in the tidal channels gradually decreased, while the traditional aquaculture ponds consistently formed a distinct cluster. Canonical correspondence analysis revealed that nutrients such as reactive silicate, reactive phosphate, and inorganic nitrogenconsistently served as the key environmental drivers for coupled ponds and tidal channels, whereas traditional aquaculture ponds were briefly dominated by pH and suspended solids, and the direction of nutrient-driven changes was opposite to that of the other two habitat types.