An aerobic, Gram-stain-negative, short rod-shaped, non-motile and non-sporulating bacterium, designed strain 8-1b(T), was isolated from seaweed collected from the intertidal zone of Zhoushan sea area, East China Sea. Strain 8-1b(T) grew at 4-39 °C (optimum, 28-32 °C) and at pH 6.0-9.5 (optimum, 7.0-8.5), and with 0.5-8% (w/v) NaCl (optimum, 1-3%) and 0.5-10% (w/v) sea salts (optimum, 2-3%). Analysis of 16S rRNA gene sequences revealed that strain 8-1b(T) was related closely to Aequorivita capsosiphonis JCM 15070(T) (96.7% similarity). The DNA G+C content of strain 8-1b(T) was 36.6 mol%. Compared with reference strains, cells of strain 8-1b(T) showed positive activities for H₂S production and utilization of D-mannose, DL-lactic acid, L-asparagine and glycyl L-aspartic acid. The major fatty acids of strain 8-1b(T) were iso-C(15:0), iso-C(17:0) 3-OH, iso-C(15:1) G and iso-C(17:1)ω9c. The main respiratory quinone was menaquinone 6. The polar lipids of strain 8-1b(T) consisted of phosphatidylethanolamine (PE), three uncharacterized aminolipids (AL1-3), four uncharacterized glycolipids (GL1-4) and five uncharacterized lipids (L1-5). Based on the phenotypic and genotypic characterization, strain 8-1b(T) represents a novel species of the genus Aequorivita, for which the name Aequorivita viscosa sp. nov. is proposed. The type strain is strain 8-1b(T) ( =CGMCC 1.11023(T) = JCM 18497(T)). Emended descriptions of Aequorivita antarctica and Aequorivita capsosiphonis are also presented.