Marine

Physical environment

Physical environment

Vast sandy beaches and barrier islands dominate the southwest coastline of Madagascar. Air temperature at sea level rarely falls below 20 C and seawater is usually between 20 and 30 C.

A total of 1000 km of coral reefs surround Madagascar. Andavadoaka's reefs are at the northern end of a reef system that stretches almost 350 km, the third largest continuous reef system in the world.

The reefs of Andavadoaka are situated between 3 and 5 km offshore.
The reef systems along Madagascar's southwest coast are more complex than anywhere else in Madagascar, comprised of shoreline fringing communities, a series of inner lagoon reefs and a barrier reef.

Winds play a critical role in this area, driving water circulation and affecting wave action, weather patterns, biological processes and human activities.

Ocean currents are also an important feature that strongly influence the distribution of marine organisms and the availability of nutrients around Andavadoaka.

Ecosystems

Ecosystems

Andavadoaka boasts one of the richest marine ecosystems on the southwest coast and has become a magnet for fishermen as well as a developing tourist industry.

The Andavadoaka region is home to a variety of marine habitats including mangroves, coral reefs, lagoons, barrier islands and rocky outcrops.

The southwest of Madagascar is also world famous for the Grand Recif barrier reef of Toliara, part of a reef system that extends more than 350 km in length, and boasts over 1000 species of reef-building corals, sponge and reef fish.

Mangroves

Madagascar is home to the largest area of mangroves in the Western Indian Ocean. Mangroves are found south of the village of Andavadoaka and provide critical habitat for a variety of terrestrial and marine species including numerous bird species that eat swamp insects above the water and shoals of fish below.

The salt tolerant trees that dominate mangrove systems straddle the water at low tide with weight-bearing roots that stick upwards, as they are unable to gain oxygen in the thick estuarine mud.

Many fish and crustacean populations use the underwater landscape of mangroves as nurseries, coming in from the sea to mate, breed and rear their young in relative safety. Mangroves also play an important role in human survival, providing natural barriers against storm surges, stabilizing coastlines, reducing erosion and supporting a variety of fish species eaten by local communities.

 

Coral Reefs

The coral reefs around Andavadoaka are some of the most remote and biologically diverse reef systems on earth, supporting hundreds of tropical fish and coral species.

The coral reefs of Andavadoaka are part of the third largest continuous coral reef system in the world, extending more than 300 km along Madagascar's southwest coast.

During a recent survey, scientists recorded 386 species of fish along the reefs of the Andavadoaka region. Of these, 20 species had never before been recorded for Madagascar.

Scientists believe that further research may reveal as many as 529 fish species living among these reefs. The survey also recorded 164 species of hard corals.

The reefs of Andavadoaka, however, are facing serious threats from climate change. Surveys found some reefs in the area that had lost 99 percent of their coral cover due to "bleaching."

A number of coral bleaching events – where rising temperatures cause corals to turn white and ultimately die – have struck Madagascar’s southwest coast over the years, the worst being in 1998 and 2000.

Coral reefs also are critical to the livelihoods and cultures of the nearby artisinal fishing communities whose economies are almost entirely marine based.

The foundation species for coral reefs, the reef-building corals, are miniature relatives of the jellyfish, who live in vast colonies, surrounding themselves with a protective skeleton of calcium carbonate and grabbing plankton out of the water with their stringing tentacles. Together these colonies can create massive reefs that serve as the home to a wide variety of fish and invertebrates.

 

There are 2 basic types of corals, the slow-growing massive corals and the more delicate branching corals, which grow ten times faster, but fracture easily in storms.

Flora and Fauna

Flora and Fauna
Marine Flora

Algae, seagrass and mangrove trees comprise the major flora of Madagascar's southwest marine systems. Algae are primitive plants, which do not have true roots, leaves or stems. An important reef-building alga is the red coralline algae, which secretes a hard limestone skeleton that can cement dead coral together.

Seagrass, as the name suggests, looks like large blades of grass growing underwater in sand near the shore. They produce flowers, fruits and seeds for reproduction. Mangroves can live in salty soil or water, and are found south of the village of Andavadoaka.

 

 

Marine Fauna

Scientists have recorded more than 350 species of tropical fish living among the reefs of Andavadoaka. More than 160 species of coral and 238 species of molluscs have also been recorded in the area.

Because there has been relatively little scientific study in the Andavadoaka region, scientists believe there are hundreds of other reef-dwelling species living in the area that have yet to be discovered.

A number of species recorded around Andavadoaka are not found anywhere else in Madagascar including the large tooth cardinal fish, the black blotched porcupinefish, the whitespotted guitar fish and the yellow spotted puffer.

Other species found in the Andavadoaka region include sharks, dolphins, sea turtles and migrating whales.

Both sea turtle and shark populations are in rapid decline in the area due to destructive overfishing. Reef fish are also being threatened from the destruction of corals due to climate change.

Many species found in Andavadoaka are listed as vulnerable, endangered or critically endangered by the IUCN red list of threatened species. These include the Napolean Wrasse, the giant grouper, the whitetip reef shark, the blacktip reef shark, the gray reef shark, the leopard/zebra shark, the green turtle, the loggerhead turtle, the humpback whale and the spinner dolphin.