Factors that structure algal communities in tropical rocky shores: What have we learned?

Abstract

Experiments in tropical rocky intertidal habitats across the globe have identified various effects of biological and physical factors on algal assemblage. High- and mid-intertidal rocky shores in tropical areas are exposed, with varying degrees, to the same physical factors such as temperature, heat, desiccation, shore height, supply of sediment and nutrients that affects temperate rocky shores. The degree of exposure to physical extremes however determines the structure of assemblage in most tropical rocky shores. The low shore is often controlled by biological factors, i.e., grazing and predation by mollusks, fishes, amphipods, crabs, and iguanas, while the high shore is mainly controlled by physical factors. It appears that the keystone species concept may not apply to tropical rocky shore communities. Reasons for this include indirect effects, overlapping food requirements and a diffuse predation due to a diverse set of assemblage that may mask the effect of one species. Present paper compare the several studies carried out in Hong Kong and Panama on tropical rocky shore consumer interactions. Studies on the effects of physical disturbances in coastal areas such as storms or typhoons are rare and there were little studies dealing with interactions of the sub tidal coralline algae and the low shore algae in tropical areas. More experimental work across a variety of spatial and temporal scales are therefore needed to determine significant biological and physical processes affecting the structure of algal assemblage across broad areas in the tropics.