Browsers feed on Macroalgae.
Grazers/detritivores intensely graze epilithic algal turfs, which can limit the establishment and growth of Macroalgae.
Suitable recruitment habitat includes a stable bottom
type, limited sedimentation in water column, and absence of large Macroalgae.
Loss of herbivores, through overfishing, can cause shifts from coral dominated reefs to reefs with abundant Macroalgae populations.
Substrates, such as live coral, sediment, Macroalgae, encrusting sponges,
and loose, unconsolidated substrate are unsuitable for coral recruit settlement.
By grazing on algae, herbivores can prevent Macroalgae from overgrowing corals or occupying space important for coral recruitment.
Herbivores play a key
role in influencing competitive interactions between corals and Macroalgae(i.e., herbivores consume algae
and create space for coral recruits to settle).
Scrapers and small excavators help control the establishment and
growth of Macroalgae while intensely grazing epilithic algal turf
and providing areas of clean substratum for coral recruitment.
Coral reefs where Macroalgae has come to dominate the reef substrate
may also need substrate enhancement interventions to make the substrate suitable for coral outplanting and natural recruitment processes.
If Macroalgae are highly abundant at a site because of low herbivore populations(e.g., due to overfishing),
coral populations have little chance of recovering because Macroalgae inhibit settlement of new corals.