Members of the genus Marinomonas are known for their environmental adaptation and metabolically versatility, with abundant proteins associated with antifreeze, osmotic pressure resistance, carbohydrase and multiple secondary metabolites. Comparative genomic analysis focusing on secondary metabolites and orthologue proteins was conducted with 30 reference genome sequences in the genus Marinomonas . In this study, a Gram-stain-negative, rod-shaped, non-flagellated and strictly aerobic bacterium, designated as strain E8 T , was isolated from the red algae ( Gelidium amansii ) in the coastal of Weihai, China. Optimal growth of the strain E8 T was observed at temperatures 25–30 °C, pH 6.5–8.0 and 1–3% (w/v) NaCl. The DNA G + C content was 42.8 mol%. The predominant isoprenoid quinone was Q-8 and the major fatty acids were C 16:0 , summed feature 3 and summed feature 8. The major polar lipids were phosphatidylglycerol (PG) and phosphatidylethanolamine (PE). Based on data obtained from this polyphasic taxonomic study, strain E8 T should be considered as a novel species of the genus Marinomonas , for which the name Marinomonas algarum is proposed. The type strain is E8 T (= KCTC 92201 T  = MCCC 1K07070 T ).