At its summit sits the most inhospitable zone of all, an impossible place where combers repetitively curl, break, then retreat: the algal ridge. Built by encrusting red seaweeds and cemented into place under the extreme forces of surf and sunlight, it is the final, seemingly insurmountable obstacle between the baby fish and the sanctuary of Moorea's inner lagoon.
After nightfall, despite having never done anything of the kind before, they will gather under the humped back of a wave, ride up its powerful rise, then down its thunderous landfall, and surf across the algal ridge.
From underwater they lift, then curl, forming beautiful, mercury-bright cylinders that barrel-roll up the barrier reef toward the algal ridge. The larger swells rear and corkscrew, appearing from underwater to pull themselves inside out until they've drawn to their full height, at which point they throw themselves onto the algal ridge, exploding in billows of blinding white bubbles.
pachydermum on settlement plates, restricting it to high energy environments such as algal ridges and reef crests.
The Choneplax lata/Porolithon pachydermum association covers substantial areas of algal ridges throughout the Caribbean [ILLUSTRATION FOR FIGURE 6 OMITTED].
In the Pacific, wave shock in the intertidal and fish grazing subtidally are sufficient to remove large frondose algal competitors from the closely related reef-builder Porolithon onkodes (Heydrich) Foslie on Hawaiian algal ridges (Littler and Doty 1975), but abundant rasping limpets are also present in the intertidal, as well as on the algal ridges of Guam and Enewetak Atoll (Littler and Littler 1984: Fig.