Abstract: Seafloor hydrothermal fluids are rich in various metal elements and could be one of the important sources of metals in the ocean. We investigated Zn species in hydrothermal plumes in different types of hydrothermal systems (water-rock and magmatic-hydrothermal systems) in the northeastern Lau Basin, Southwest Pacific, including particulate Zn (pZn), dissolved Zn (dZn), and colloidal Zn (cZn). Results show that the plumes contained higher pZn concentrations than background seawater (typically <0.5 nM) in maximum of 16.9 nM. In plumes from low-temperature magmatic-hydrothermal systems, pZn concentrations were comparatively low, but still higher than that in background seawater. Even in the plumes that originated from low-temperature venting at West Mata that had dispersed off to over 5 km, the pZn concentration could still reach 3.1 nM, which indicates that pZn did not precipitate rapidly but dispersed in the ocean with the plumes, and the seafloor hydrothermal systems could be one of the sources of pZn in the ocean. The analyses of dZn in the plumes revealed no significant difference in dZn concentration between the two types of hydrothermal systems. Although the input of hydrothermal fluids resulted in higher dZn concentrations in some plume samples compared to background seawater, the adsorption by particulate Fe led to lower dZn concentrations in other plume samples. Therefore, hydrothermal plumes could act as either a source or a sink of dZn in the ocean. Observations in scanning electron microscopy and energy-dispersive X-ray spectroscopy suggest that the cZn in plumes could be from volcanic eruption.