It is one of the largest known reef systems in the world, with scientists estimating its length at over 1,000 kilometres (600 miles), and its area as over 9,300 km2 (3,600 sq mi).
[8] The reef's area extends as far as 120 km (75 mi) offshore,[9] and is estimated to lie in waters ranging from 30 to 120 metres (100 to 400 feet) deep.
Southern sections of the reef, which are covered by the Amazon's plume only three months a year on average, are more populated with diverse coral-centric life, where photosynthesis can occur.
[5] It is believed that single-celled organisms are central to the reef's ecosystem, providing the main source of nutrients to sponges, corals and other inhabitants.
[18] Further evidence also appeared in 1977, when reef fish were first sighted in the area,[11][19] and in 1999, when Caribbean-native coral species were found in isolated regions near the Amazon Delta.
[9] However, no major study into the existence of a reef system occurred until 2012, when an international research team of over 30 oceanographers,[13] led by Rodrigo Moura of the Federal University of Rio de Janeiro, and including patrons from the University of Georgia,[11] conducted a survey of the area aboard the RV Atlantis.
The survey was mostly based on findings from the 1970s, including a crude map of the area marked with potential locations of reefs along the Amazonian coast.
[citation needed] Their discoveries and findings were detailed and presented in a research article published in the scientific journal Science Advances in April 2016.
[23] In the past decade, the Brazilian government had sold 80 license blocks to oil energy companies in the region, with an environmental baseline based on "sparse museum specimens".