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Reefs at risk

Coral reefs and salinity

Coral reefs are shallow-water tropical and subtropical communities, with exceedingly complex interrelationships among species: they have arguably the highest species diversity of any marine community.
Their productivity is driven by two main components: symbiotic algae (zooxanthellae) that live inside reef-building corals, and some other invertebrates and free-living algae, especially benthic seaweeds.
The growth of the reef structure itself depends upon calcification by corals and coralline algae, and thus upon adequate light for photosynthesis: they are therefore sensitive to reductions in light penetration from increased turbidity.
Reefs typically form in oligotrophic waters within a relatively narrow range of temperature and salinity, and tend to grow in temperatures near the upper limits of tolerance for the corals that build them.
Thus, reef communities are sensitive to relatively small changes in temperature and salinity.