The Amazon Reef, a recently discovered marine ecosystem, lies off the coast of French Guiana and northern Brazil. Its existence was unexpected due to its location at the mouth of the Amazon River, an environment previously thought unsuitable for such structures. This discovery has generated scientific interest, challenging prior understandings of marine habitats.
Discovery and Distinctive Features
The Amazon Reef’s discovery was announced in April 2016, following an oceanographic study conducted in 2012 by an international team of scientists. While earlier indications of a large structure near the Amazon Delta date back to the 1950s and 1970s, detailed mapping came much later. The reef system stretches an estimated 600 miles (1,000 kilometers) and covers an area of over 3,600 square miles (9,300 square kilometers), potentially reaching up to 21,600 square miles (56,000 square kilometers).
This reef defies conventional expectations because large rivers typically create “gaps” in reef systems due to their freshwater plumes, which reduce salinity, pH, light penetration, and increase sedimentation. The Amazon Reef thrives despite these conditions, primarily due to its depth, ranging from about 100 to 400 feet (30 to 120 meters), with some parts extending as deep as 720 feet (220 meters). This depth places it below the direct influence of the Amazon River’s freshwater layer, which accounts for one-fifth of the world’s freshwater outflow into the ocean daily.
The reef’s composition is distinctive; it is largely made up of rhodoliths, which are calcareous nodules formed by red algae, rather than the stony corals that dominate typical tropical reefs. While some corals are present, especially in southern areas that experience less of the Amazon plume, sponges and rhodoliths are the primary builders of this ecosystem. The deeper, murkier waters also mean that its energy production relies more on chemosynthesis and microbial processes than on photosynthesis.
Ecological Significance
The Amazon Reef supports a diverse array of marine life, despite its unusual conditions. Scientists have identified over 60 species of sponges, including three new species, and 73 species of fish, along with spiny lobsters and brittle stars. The reef’s northern sections, often under the river’s sediment plume for six months or more annually, are home to sponges and carnivorous organisms like hydroids. In contrast, the southern areas, which receive more sunlight due to less plume coverage, host more diverse coral-centric life.
This ecosystem serves as a stepping stone, facilitating the dispersal of species between reefs in southern Brazil and the Caribbean. It also functions as a potential nursery ground or a migratory route for various marine animals. Whales, dolphins, and sea turtles, for example, use the Amazon Reef region for migration, and it is a confirmed birthing and feeding ground for whales. Microorganisms thriving in the low-light conditions beneath the river plume also provide a trophic connection, forming the base of the food chain for sponges, corals, and other inhabitants.
Threats and Conservation
The Amazon Reef faces threats, primarily from potential oil and gas exploration activities in its vicinity. Since 2013, several oil companies have sought to exploit the Amazon Mouth basin, an area estimated to hold significant fossil fuel reserves, some of which overlap directly with the reef system. The Brazilian government has already sold 80 blocks for oil exploration and drilling at the Amazon’s mouth, with 20 of these already producing oil.
The unique and fragile nature of the Amazon Reef makes it vulnerable to the risks associated with oil drilling, such as spills. An oil leak in this region could cause irreversible damage, affecting not only the reef but also the coast and the rivers of the Amazon Delta, which include the world’s largest mangrove forests. Such an event would also impact local fishing communities, extractive communities, river villages, and indigenous populations who depend on these ecosystems.
In response to these threats, scientists, environmental organizations like Greenpeace, and local communities have been advocating for the reef’s protection. Greenpeace, for example, has conducted expeditions to collect biological samples and document the reef’s biodiversity, aiming to highlight its importance and the risks it faces. These groups often call for moratoriums on drilling and have successfully campaigned against drilling licenses in the past. However, with less than 5% of the reef’s potential area surveyed, comprehensive risk assessment for oil and gas exploitation remains challenging, underscoring the need for precautionary conservation measures.