| Coral reefs cover about 600 000 km2,
which is 15% of the ocean bed, between 0 and 30 metres. The coasts of more
than a hundred mainly underdeveloped countries have reef structures which
are far from being negligible for local commerce and in shore-line protection.
Coral reefs are found between latitudes 30°North and 30°South. Their
extension is mainly limited by temperature, salinity, and the sediment-load
of seawater. The active part of a coral reef is no deeper than 80 to 100m,
according to light penetration and turbidity. Salinity is an important factor
in their distribution and they are not found near big deltas such as the
Ganges or the Amazon. Thus, distribution zones of coral reefs and their
specific richness, are determined by environmental factors. Biogeographic
factors generated by these factors can either be correlated to the latitude
(temperature, light and currents) or not (substrate quality, water quality,
nutrients, local ecology and regional dispersion barriers). |
