INTERTIDAL AMPHIPODS AS POTENTIAL DISPERSAL AGENTS OF CARPOSPORES OF IRIDAEA-LAMINARIOIDES (GIGARTINALES, RHODOPHYTA)

Mid and late successional benthic algae have poor dispersal capacities. Mobile herbivores may increase dispersal of some algae because spores can survive digestion by grazers and stick to external body appendages. We show that carpospores are the only type of reproductive unit of the rhodophyte Iridaea laminarioides Bory that survive passage through the digestive tract of the amphipod Hyale sp. The spores also stick to the amphipods' legs and are thus carried by the amphipods in the field. Amphipods significantly increased (P < 0.01) the number of spores settling on artificial substrata in places where barriers prevented the normal ingress of algal propagules. The presence of artificial substrata that act as a refuge for the grazers also caused an increase (P < 0.01) in the number of settled spores. Amphipods also significantly increased (P < 0.01) the number of spores under an Ulva sp. canopy in laboratory experiments.