The Environmental Gradient

Exposed Zones

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Aquarists, Divers and Snorklers are very familiar with the exposed zone of natural reefs. It is the upper and outer areas of a tropical reef platform. Intense to low light levels occur and water currents vary from intense to low. Animals that live within the shallow water areas of this zone need to be able to shield themselves from the intense UV light that occurs within the tropics. Many human vacationers have quickly and painfully learned that UV light levels are intense within the region. Traditional reef aquariums have been primarily composed of exposed zones. These zones are actually major producers of organic matter. This is primarily due to the photosynthetic animals that incorporate inorganic carbon into organic carbon molecules. Reef aquairums that only contained exposed zones have required protein skimmers or carbon or filter pads or ozone to handle these excess organic particules. More natural methods have included algal sumps, sediment plenums, mud sumps and deep sediment beds. The EG system establishes other zones that are specifically setup to process particulate organics, dissolved organics and excess bacterial populations produced within the exposed zone.

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