Abstract Fronds had higher mean caulerpenyne concentration than stolons in Caulerpa prolifera, C. taxifolia and C. racemosa. C. prolifera had higher mean caulerpenyne content [7.29±0.64% caulerpenyne/frond dry weight (DW)] than C. taxifolia (5.47±0.32% caulerpenyne/frond DW) and C. racemosa (0.43±0.07% caulerpenyne/frond DW). C. prolifera had reduced content from May to October in fronds, with no clear seasonal pattern in stolons. C. taxifolia reached a maximum caulerpenyne value in fronds in May, with a slight decrease until the onset of winter; there was no clear seasonal trend in stolons. Caulerpenyne content remained relatively constant through the year in fronds of C. racemosa; stolons showed a clear seasonal pattern of increasing caulerpenyne content in spring, reaching maximum values at the end of summer, and decreasing during winter. C. prolifera caulerpenyne contents were positively correlated with densities of the Caulerpa-feeding gastropod Ascobulla fragilis (ρ=0.84, p<0.05). The main finding of the present work is that C. prolifera has higher caulerpenyne concentrations than invasive Caulerpa species under similar climate conditions.