A short-term response of macroalgae to potential competitor removal in a mid-intertidal habitat in Korea

Interspecific interactions among three dominant macroalgae, Pterocladia capillacea (Rhodophyta), Hizikia fusiformis (Heterokontophyta) and Chondracanthus intermedius (Rhodophyta), were experimentally investigated on the rocky mid-intertidal zone of Sungsan, Jeju Island, Korea from March 1998 to June 1999. Each of the potentially competing species was removed in permanent plots (20 x 20 cm), and percent covers of non-manipulated species were measured by an image analyzing method using a digital camera. Pterocladia capillacea was the most abundant during all seasons, except for winter. Its abundance was lowered by the removal of the turf-forming alga C. intermedius, indicating that turf had a positive effect on P. capillacea. Conversely, there was a negative effect of P. capillacea on the abundance of C. intermedius. Interactions between C. intermedius and P. capillacea can probably be explained as a consequence of the water-trapping ability of the former and the canopy-forming ability of the latter. There was, however, no apparent effect related to H. fusiformis since the abundance of this alga remained low. This study supports that both negative and positive effects between same pair of species could be common depending on the morphological differences of algae and particular habitat conditions.