The outbreak of vibriosis from Vibrio parahaemolyticus (V. parahaemolyticus) is one of common pathogenic diseases found in the mariculture environment. In this study, the inhibitory effect of Ulva fasciata (U. fasciata) on the culturability, motility, and biofilm formation of V. parahaemolyticus ATCC17802 was examined by co-culturing system. Results showed that both of secretion and live tissue of U. fasciata could convert culturable V. parahaemolyticus ATCC17802 to non-culturable, both reaching more than 99% of inhibition rate after 3-day co-culture, and higher density (12 g L⁻¹) of U. fasciata exhibited stronger inhibition. The twitching behavior of V. parahaemolyticus ATCC17802 was more easily affected by U. fasciata than the swimming behavior after 3-day co-culture, with the inhibitory rates varying at the ranges of 1.70–30.29% (twitching behavior) and 10.06–44.86% (swimming behavior) under the different environmental factors (salinity, NO₃⁻-N and PO₄³⁻-P concentrations), but no significant correlation was found. The greatest inhibition effect on V. parahaemolyticus ATCC17802 biofilm formation occurred at 12 h, with inhibition rates at the range of 11.03–67.10 %, while there was still no significant correlation between inhibition rate and the three environmental factors. The different environmental factors might induce U. fasciata to excrete different levels of secondary metabolites, which caused the various inhibitory effect on the cultivability, motility, and biofilm formation of V. parahaemolyticus ATCC17802.

副溶血性弧菌（V. parahaemolyticus）爆发的弧菌病是海水养殖环境中常见的病原菌之一。本研究通过共培养系统研究了石莼（U. fasciata）对副溶血性弧菌ATCC17802的可培养性、运动性和生物膜形成的抑制作用。结果表明，U. fasciata的分泌物和活组织均可将可培养的副溶血性弧菌ATCC17802 转化为不可培养的，共培养 3 天后均达到 99% 以上的抑制率，并且密度更高（12 g L ^{- 1} ) U. fasciata表现出更强的抑制作用。共培养3天后副溶血性弧菌ATCC17802的抽搐行为比游泳行为更容易受到U. fasciata的影响，抑制率在1.70-30.29%（抽搐行为）和10.06-44.86%之间变化（游泳行为）在不同环境因素（盐度、NO ₃ ^- -N 和PO ₄ ^3- -P 浓度）下，但未发现显着相关性。对副溶血性弧菌抑制作用最大ATCC17802 生物膜形成发生在 12 h，抑制率在 11.03-67.10% 范围内，而抑制率与三个环境因素之间仍然没有显着相关性。不同的环境因素可能会诱导U. fasciata分泌不同水平的次生代谢产物，从而对V. parahaemolyticus ATCC17802的可培养性、运动性和生物膜形成产生多种抑制作用。