The Amazonia

marine ecoregion A marine ecoregion is an ecoregion, or ecological region, of the oceans and seas identified and defined based on biogeographic characteristics. Introduction A more complete definition describes them as “Areas of relatively homogeneous species ...

covers the coastal marine environment off the mouth of the Amazon River on the continental shelf of

Brazil Brazil, officially the Federative Republic of Brazil, is the largest country in South America. It is the world's List of countries and dependencies by area, fifth-largest country by area and the List of countries and dependencies by population ...

. The warm North Brazil Current moves east-to-west across the river's outlet, carrying turbid, fresh water to the northwest towards the

Caribbean Sea The Caribbean Sea is a sea of the Atlantic Ocean, North Atlantic Ocean in the tropics of the Western Hemisphere, located south of the Gulf of Mexico and southwest of the Sargasso Sea. It is bounded by the Greater Antilles to the north from Cuba ...

. The Amazonia is one of two ecoregions (the other being the Guianan marine ecoregion) in the North Brazil Shelf province, a large marine ecosystem (LME). It is thus part of the Tropical Atlantic realm.

Physical setting

The ecoregion is bounded on the west at the Brazil-French Guiana border, where the North Brazil Current splits - part continuing northwest as the Guiana Current, part turning north. 850 miles to the southeast, the ecoregion transitions to the

Northeastern Brazil marine ecoregion The Northeastern Brazil marine ecoregion covers the coastal marine environment around the Northeast Region, Brazil, Northeast Region of Brazil. The marine ecoregion extends from the mouth of the Parnaíba River in the west around the eastern point ...

at the mouth of the Parnaiba River. The Amazonia ecoregion extends 200 miles offshore from the coast, covering the shelf and slope of the continental shelf. The bordering coast is low and flat, and characterized by

mangrove forest Mangrove forests, also called mangrove swamps, mangrove thickets or mangals, are productive wetlands that occur in coastal intertidal zones. Mangrove forests grow mainly at tropical and subtropical latitudes because mangrove trees cannot withsta ...

s of the Amapá mangroves terrestrial ecoregion, the sandy forests of the Northeastern Brazil restingas, and the

Marajó várzea The Marajó várzea (NT0138) is an ecoregion of seasonally and tidally flooded várzea forest in the Amazon biome. It covers a region of sedimentary islands and floodplains at the mouth of the Amazon that is flooded twice daily as the ocean tides ...

(floodplain forest) of the Amazon delta. Aside from the Amazon, the major rivers feeding the Amazonia marine region include the clearwater

Tocantins River The Tocantins River ( , Parkatêjê dialect, Parkatêjê: ''Pyti'' ɨˈti is a river in Brazil, the central fluvial artery of the country. In the Tupi language, its name means "toucan's beak" (''Tukã'' for "toucan" and ''Ti'' for "beak"). It ...

and the

Mearim River The Mearim River () is a river in Maranhão state of northern Brazil. The river originates in the southern part of Maranhão, and drains north into the Baía de São Marcos, an estuary that also receives the Pindaré and Grajaú rivers, which ar ...

. The continental shelf is relatively smooth and shallow, with a drop on the shelf about half-way to the north. The deepest point is , and the average is . 38% of the ecoregion is less than 200 meters in depth, and 54% is greater than 1,000 meters. Underneath the freshwater outflow of the Amazon is a carbonate reef structure, the

Amazon Reef The Amazon Reef, or Amazonian Reef, is an extensive coral reef, coral and sponge reef system, located in the Atlantic Ocean off the coast of French Guiana and northern Brazil. It is one of the largest known reef systems in the world, with sci ...

. This deep reef is colonized by sponges and other filter feeders, under conditions of low light and dense particulates.

Currents and climate

Flowing northwest through the ecoregion is the warm North Brazil Current (NBC), the northern continuation of the Central)

South Equatorial Current The South Equatorial Current are ocean currents in the Pacific, Atlantic, and Indian Ocean that flow east-to-west between the equator and about 20 degrees south. In the Pacific and Atlantic Oceans, it extends across the equator to about 5 degre ...

bringing warm water from the

South Atlantic Ocean The Atlantic Ocean is the second largest of the world's five borders of the oceans, oceanic divisions, with an area of about . It covers approximately 17% of Earth#Surface, Earth's surface and about 24% of its water surface area. During the ...

. The NBC is additionally fed by the outflow of the Amazon River, lowering the salinity and raising the turbidity of the water through the Amazonia marine area. In the summer and fall, the NBC generates counter-cycles that flow north into the

Equatorial Counter Current The Equatorial Counter Current is an eastward flowing, wind-driven current which extends to depths of in the Atlantic, Indian, and Pacific Oceans. More often called the North Equatorial Countercurrent (NECC), this current flows west-to-east at ...

(and the North Atlantic); in the spring the NBC continues straight through the Amazonia ecoregion to feed the Gianan Current and eventually the

. The NBC flows at a rate averaging 26

Sverdrup In oceanography, the sverdrup (symbol: Sv) is a non- SI metric unit of volumetric flow rate, with equal to . It is equivalent to the SI derived unit cubic hectometer per second (symbol: hm3/s or hm3⋅s−1): is equal to . It is used almost ...

s (Sv), at a mean speed of during the winter months, then slacks off somewhat in the summer as the

Intertropical Convergence Zone The Intertropical Convergence Zone (ITCZ , or ICZ), known by sailors as the doldrums or the calms because of its monotonous windless weather, is the area where the northeast and the southeast trade winds converge. It encircles Earth near the t ...

(ITCZ) shifts north. The winds over the surface range from northeasterly to southeasterly. A large outflow of fresh and brackish water from the Amazon mouth - the Amazon

river plume A river plume is a Fresh water, freshened water mass that is formed in the sea as a result of mixing of Surface runoff, river discharge and saline seawater. River plumes are formed in coastal sea areas at many regions in the World. River plumes ge ...

- extends through the middle of the Amazonia ecoregion, being pulled north by the NBC. Combined with rainfall this lowers the salinity of the ecoregion's waters, to levels that average 35-36.75 ppm. Surface temperatures range from .

Animals / Fish

The coast is dominated by the Amazon delta and extensive mangrove forests. The inlets, swamps and lagoons provide shelter, food, and breeding habitat for birds, invertebrates and fish. Offshore, the continental shelf supports soft mud-bottom communities. Aside from the Amazon Reef structure, the bottom is mostly sand, mud and gravel in the deeper water. Near shore, the most important commercial fisheries are for shrimp, primarily Southern brown shrimp ('' Farfantepenaeus subtilis'') and Red spotted shrimp (''

Farfantepenaeus brasiliensis ''Farfantepenaeus'' is a genus of prawns in the family Penaeidae. Its eight species were formerly included in the genus '' Penaeus''. It was first published as a genus name in 1972 by Rudolf N. Burukovsky, but without the necessary designation of ...

'').

Conservation status

Many of the terrestrial protected areas on the coast have marine components, such that about 12% of the ecoregion is protected, including: * Cabo Orange National Park. Marine zone extends 10 miles out from extensive wetlands (a RAMSAR site). * Algodoal-Maiandeua Environmental Protection Area. Two islands at the mouth of the Amazon, with mangroves important for their role as nurseries for fish, mussels, shrimps, oysters, turtles, crabs and other marine life.

References

{{reflist Marine ecoregions