Eukaryotic Plankton Exhibit High Community Connectivity in the Indo‐Pacific Convergence Zone Across Tropical and Subtropical Oceans

Aim Eukaryotic plankton distribution is considered not limited by dispersal in oceans. However, the Tara Oceans expedition indicated eukaryotic plankton communities are homogenised only at basin scale. Community connectivity of plankton remains largely unexplored. Here, surface seawater samples were collected from the Indo‐Pacific Convergence Zone (IPCZ), combined with the reanalysis of the Copernicus data and data of 35 stations from the Tara Oceans, to explore community connectivity across global oceans. Location The IPCZ and tropical and subtropical oceans. Time From 2021 to 2022. Taxa Eukaryotic plankton. Methods We performed a meta‐analysis of the Tara Oceans and Copernicus database and samples collected from the IPCZ to investigate eukaryotic plankton diversity and connectivity through metabarcoding. Results About 11% of eukaryotic plankton were ubiquitous based on the Tara Oceans data, and 20%–30% were shared by adjacent basins. The highest proportion was shared by the Indian Ocean (IO) and the Pacific Ocean (PAC). In the IPCZ, communities of the PAC and IO were more similar with a higher diversity compared with those from marginal seas. Salinity explained the differences between the ocean and marginal sea communities. The contribution of eukaryotic plankton community in the ocean to that in marginal seas was more than that of marginal seas to the ocean, which was consistent with the centre of accumulation hypothesis. In spring, eukaryotic plankton were transported from the PAC to IO through the South China Sea (SCS) and Sunda Strait. In summer, they were transported from the IO to SCS through the Malacca Strait under monsoon influence. Dispersal ability of different taxonomic groups in certain regions was similar, but community connectivity varied. Conclusions Eukaryotic plankton community exhibits high connectivity in the IPCZ across tropical and subtropical oceans. Ocean currents are important carriers of microbial dispersal, while monsoon‐driven hydrographic variations, particularly salinity fluctuations, shape community connectivity.