2. VIEW: Corals (BrainPop)

coral
Shallow corals are limited to growing in the photic zone. In contrast, deep sea corals can grow in the aphotic zone. Photo courtesy of Sam and Ian/Flickr.

Coral reefs are delicate ecosystems. Corals are found all over the Earth's oceans, but most coral reefs are found in tropical waters. Coral colonies grow between 1-10 cm per year, and can live for decades or centuries.



Deep sea corals are not as well-known as their shallow water counterparts (which live in the neritic zone). While shallow water corals can grow only in the photic zone, where sunlight is plentiful, deep sea corals are not limited by sunlight. Deep sea corals obtain energy by feeding on other organisms, and can therefore survive in the aphotic and abyssal zones. Deep sea corals can live at ocean depths of up to 6,000 meters and are distributed throughout the world's oceans. The global distribution of deep sea corals is determined by the Earth's thermohaline circulation, which controls the chemistry (e.g. salinity) and temperatures of the oceans. Scientists often use the shells of deep sea corals to obtain a record of changes in temperature and salinity of the world's oceans over time, in order to better understand global changes in climate and ocean currents.