Explosive blasting to construct boat channels across reef platforms is widespread in the Pacific Islands. This study describes the first ecological impact assessment of this form of development, examining effects on intertidal molluscs, crustaceans and algae, as well as physical characteristics
of the substratum. There were some increases and some decreases in the species richness of mobile invertebrates and sessile organisms, abundance of mobile invertebrates, and cover of sessile organisms, depending on the channel examined. That is, although we could detect effects we could not
detect general effects, either in terms of the magnitude or the direction of the response. The 18 significant effects detected on organisms were almost equally divided between increases and decreases at channel sites compared to controls. The effects that did arise tended to be localised (less
than 20 m from channel) and in most cases were small in magnitude, compared to the natural site to site variation along the reef platform. We suggest that the types of effects observed relate to the individual hydrological and physical habitat conditions at each channel site, as well as the
type or age of channels, but a more extensive survey is needed to test this. In conclusion, channels do appear to have long-term ecological effects on intertidal organisms, but their magnitude and spatial extent suggest that this alone is not a major environmental problem on the scale of whole
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