Marine

Marine 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.

Velondriake’s reefs are at the northern end of the world famous Grand Recif barrier reef system that stretches almost 350 km, the third largest continuous reef system in the world. These reefs are situated between 3 and 5 km offshore, and 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 also strongly influence the distribution of marine organisms and the availability of nutrients around Velondriake, making this area one of the richest marine ecosystems on the southwest coast and therefore a magnet for fishermen as well as a developing tourist industry.

 

Mangroves

Madagascar is home to the largest area of mangroves in the Western Indian Ocean. These salt-tolerant trees straddle the water at low tide, and provide valuable habitat for marine creatures. Many fish and crustacean populations use the underwater mangrove forests as breeding areas and nurseries where juveniles are in relative safety, while the upper canopy is home to terrestrial species including numerous birds.

Mangroves are also important for local human populations, providing natural barriers against storm surges, stabilizing coastlines, reducing erosion, providing fuelwood and construction material, and supporting a variety of fish harvested by local communities.

Threats

Unfortunately, many of these mangrove forests are quickly degrading due to overharvesting for fuelwood.  In addition, seining (fishing with nets) in the mangrove forests is particularly destructive as it targets the juvenile fish inhabitants. 

 

 

 

 

 

 

 

 

Coral Reefs

Reef-building corals live in vast colonies, surrounding themselves with a protective skeleton of calcium carbonate. Together, these colonies can create massive reefs that serve as the home to a wide variety of fish and invertebrates.  There are two 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. A recent survey recorded 164 species of hard corals within the Velondriake area.

Threats
The reefs of Velondriake, however, are facing serious threats from climate change. Rising water temperatures and increased alkalinity due to CO2 absorption are causing corals to bleach and die; surveys found some reefs in the area had lost 99% of coral cover due to bleaching.

In addition, destructive fishing practices are harmful to the coral reefs.  Certain beach seining nets drag along the sea floor, damaging delicate reefs.  Over fishing in general – regardless of the equipment used – also negatively affects coral reefs by disrupting the ecosystem balance.

 

 

 

 

Flora and Fauna

Marine Flora

Algae, seagrass and mangrove trees comprise the major flora of Madagascar's southwest marine systems. Algae are primitive plants, lacking true roots, leaves or stems. Red coralline algae are important in reef building, secreting a hard limestone skeleton that can cement dead coral together.  Seagrass, as the name suggests, resembles large blades of underwater grass found in sand near the shore; these plants produce flowers, fruits and seeds for reproduction.

 

Marine Fauna
During a recent survey, scientists recorded more than 380 species of fish along the reefs of the Velondriake region, of which 20 species had never before been recorded in Madagascar.  More than 160 species of coral and 238 species of molluscs have also been recorded.

This area contains a number of endemic species - recorded around Velondriake but 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 Velondriake region include sharks, dolphins, sea turtles and migrating whales.  Both sea turtle and shark populations are in rapid decline due to destructive fishing practices and an increasing fishing pressure.

Many species found in Velondriake 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 white tip reef shark, the black tip reef shark, the gray reef shark, the leopard/zebra shark, the green turtle, the loggerhead turtle, the humpback whale and the spinner dolphin.

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