Kelp beds have a complex vertical structure, like a forest. Major component of reefs is coral. The stony framework of a coral reef is built by animals, who have a mutualistic relationship with photosynthetic algae. Coral reefs are extremely productive. Thus, coral reefs can hold large concentrations of nutrients in their biomass although the open ocean around them may be nearly devoid of nutrients.
Reefs occur in mainly tropical seas, but can be killed if the ocean temp gets too high.
Submergence alternating with direct exposure to the sun Battering by waves Temperature fluctuations Salinity changes, especially in tide pools Many organisms adapt by waiting out low tide buried in mud or hidden in rock crevices. A salt marsh is a marine-shore ecosystem dominated by herbaceous plants. Mostly in temperate climates on sandy shores. A mangrove forest is a forest dominated by salt-tolerant woody plants, mostly in tropical and subtropical climates. Salt marshes and mangrove forests are affected by tidal movements.