Description :

Mangroves are the only trees capable of living in saline water (halophile species).

There are four main species of mangroves, each adapted to the salinity, soil, and environment in which they thrive:

The Red Mangrove (Rhizophora mangle)

It is recognized by its aerial stilt-like roots, which serve two purposes:

1. To provide the tree with a better foundation, resisting mud erosion.
2. To supply the tree with oxygen, improving gas exchange with the atmosphere.

This aerial root network also helps maintain sediment and provides shelter and hiding places for a rich fauna.

Its leaves are broad, thick, round and opposite.

You can also recognize its yellow flowers, which appear from June to September.

Its fruits are torpedo-shaped seedlings. The mangrove sheds them when the tide is low; this is a strategy the tree uses to reproduce. Once stuck in the mud, the seedling begins to grow.

• Black mangrove (Avicennia germinans)

This mangrove tree is recognizable by two factors :

1. Its trunk is gnarled and deformed.
2. Its trunk is surrounded by numerous pencil-shaped (very thin) pneumatophores.

Pneumatophores are hollow tubes that bring air to the roots to supply the tree with oxygen. They emerge from the soil or water and resemble stems.

In addition, its elongated, narrow, and opposite leaves harbor salt crystals on their undersides. They often contain holes due to salt saturation. Note that this mangrove tree is more resistant (than others) to extremely saline conditions.

They are found upstream of the red mangroves in shallow salt waters.

The black mangrove also has flowers; they are white, have four petals, and bloom between April and August. Its fruit is oval and flat, measuring between 2 and 3 centimeters.

• The white mangrove (Laguncularia racemosa)

This mangrove is a tree with drooping branches. It is also accompanied by pneumatophores, but these are shorter and thicker than those of the black mangrove. Growing upstream from the black mangroves, it tolerates brackish water.

It is recognizable by the reddish tint at the base of its opposite leaves. They are leathery and rounded, bordered with very small glands on both sides.

The flowers are small and white, seen between January and July. The fruits resemble small gourds, pale green, almost oval.

• The gray mangrove (Conocarpus erectus)

This mangrove does not grow directly in water like the previous one. It is the only mangrove that has neither stilts nor pneumatophores.

It prefers the seaside, sandy, or rocky areas. Its leaves are narrow but leathery and alternate. It has very small green flowers, present between April and July. The fruits are in clusters and are rounded and brown.

Habitat :

Mangrove trees thrive in a biodiverse environment: the mangrove.

This environment, found only in tropical areas, provides a nursery for numerous species of birds, invertebrates, crabs, and fish, which come to breed or feed.

It acts as a wave breaker and protects the coast from the swell. A well-preserved mangrove can reduce wave power by 75% and allows for drainage of the surrounding areas.

While all mangrove trees are found in this environment, they are also distributed, depending on their type, in various areas of the mangrove.

Red mangroves are found directly in the water and in the mud (a very suffocating environment), black mangroves are upstream of the red mangroves, white mangroves are in front of the black mangroves, and gray mangroves are along the seashore.

Threat Factors

The mangrove is still a victim of pollution today, particularly the dumping of bulky waste near it. This highly degradable pollution has a considerable impact on the life of this biodiversity hotspot.

This environment was also long considered undesirable and of little importance. It has therefore been affected by urbanization. In Guadeloupe, for example, the airport, the Gabarre landfill, and the Jarry industrial zone were built directly in this ecosystem. Fortunately, today, the mangrove is an ecosystem that is protected worldwide.