In intertidal zones, macroalgae constitute important habitats for small benthic animals and plants. These associated benthic organisms may select macroalgae depending on different environmental and habitat conditions, including algal morphological complexity. In this respect, algae with variable morphological structure such as Sargassum thunbergii may be considered an ideal subject for a comparative study of algal-animal relations. Further, in the subtropical intertidal of western Kyushu, S. thunbergii co-occurring with corallina algae appeared to be in better growth conditions than solitary conspecifics. This in turn implies that S. thunbergii occurring with corallines may provide a better refugia to animals.
    The present study has been aiming to investigate some of these variable relationships through analysis based on quantitative field sampling. Our observations have revealed that coralline beds may reduce physical disturbances and thereby protect co-occurring brown algae, which in turn could lead to a greater abundance and diversity of associated organisms.