Shallow marine waters
Biogenic carbonate production is inhibited by the
presence of clastic material so the areas of low input
of detritus are potential sites for carbonate deposition.
Under favourable conditions, the amount of biogenic
carbonate produced in shallow seas is determined by
the productivity within the food chain. Photosynthetic
plants and algae at the bottom of the food
chain are dependent on the availability of light, and
penetration by sunlight is controlled by the water
depth and the amount of suspended material in the
sea. Relatively shallow waters with low amounts of
suspended terrigenous clastic material are therefore
most favourable and in bright tropical regions with
clear waters this photic zone may extend up to 100m
water depth (Fig. 15.1) (Bosscher & Schlager 1992).
Photosynthetic organisms typically flourish in the
upper 10 to 20 metres of the sea and it is in this
zone that the greatest abundance of calcareous organisms
is found. This shallow region of high biogenic
productivity is referred to as the carbonate factory
(Tucker & Wright 1990). Increased or reduced salinity
inhibits production and the optimum temperature
is around 20 to 25°C. Hermatypic corals
dependent on symbiotic algae are most productive in
shallow clear water with strong currents, while most
other benthic marine organisms prefer quieter waters.