Marine mesograzers can consume large quantities of biomass and are a major threat for macroalgal populations. It is known that many seaweed produce secondary metabolites against herbivory, and it is a widespread notion that the allocation of defensive compounds is costly. If this is true, the ability to defend should be reduced under conditions of environmental stress. To asses the effects of low-light stress on macroalgal, we kept seaweed Chondrus yendoi under 6 different light regimes and subsequently conducted feeding assays. Additionally, we checked for the presence of an inducible defense in C. yendoi, by adding herbivores to half of the experimental units during the stress induction phase. 2 grazers were here: Lacuna smithii (Gastropoda) and Idotea ochotensis (Isopoda). A significant effect of light reduction on algal palatability was detected for L. smithii but not for I. ochotensis, while an effect of the grazing history was found as a response to grazing by I. ohotensis but not by L. smithii. From these results, we can infer that C. yendoi has 2 different defence. One is a constitutive defence which was affected by light intensities, and the another is inducible defence which is not affected by light intensity.