Underwater life

…rth Atlantic to breed in tropical waters.

Humpback whales are generally observed between January and April, when adults and calves appear in the channel between Guadeloupe and Marie-Galante. The waters of Guadeloupe are also home, more rarely, to the Physeter macrocephalus (sperm whale), which is found in deeper waters beyond the island plateau. The West Indian manatee, Trichechus manatus, once present, has been locally extinct since the mid-20th century, mainly due to hunting and habitat degradation.

However, marine mammal populations now benefit from protective measures, allowing healthy groups of dolphins to be observed on a regular basis. Observation at sea, regulated by legislation, allows visitors to witness the hunting, communication, and socialization behaviors of these animals without disturbing them.

Coral reefs and associated fauna

Guadeloupe's coral reefs grow in shallow waters, between 0 and 30 meters deep, mainly south of Grande-Terre and around the islands of the Saintes archipelago. They are formed by reef-building corals such as Acropora palmata (elkhorn coral), Acropora cervicornis (deerhorn coral) and massive corals such as Montastraea cavernosa. There are more than 50 species of hard coral in Guadeloupean waters. These reefs provide shelter and nurseries for a multitude of fish species such as Acanthurus chirurgus (brown surgeonfish), Sparisoma viride (parrotfish), Haemulon flavolineatum (yellow-lined grunt), and Epinephelus striatus (Nassau grouper), which is now endangered.

The reefs are also home to crustaceans (lobsters, cleaner shrimp), mollusks (whelks, conch), and sponges. The three-dimensional structure of the reef, created by the accumulation of coral colonies over several decades, provides refuge for the juveniles of many commercial species, indirectly contributing to local fishery resources.

However, coral cover has declined due to bleaching caused by rising temperatures, diseases (such as White Band Disease) and anthropogenic pressure (coastal pollution, boat anchoring). Local restoration initiatives (coral propagation, fishing bans in certain areas) are being implemented to maintain and rehabilitate these precious habitats.

Sea turtles

Sea turtles found in Guadeloupe include Chelonia mydas (green turtle), Eretmochelys imbricata (hawksbill turtle), Dermochelys coriacea (leatherback turtle) and, more occasionally, Caretta caretta (loggerhead turtle).

• The green turtle, which is herbivorous, frequents coastal seagrass beds where it grazes on marine phanerogams, while the hawksbill turtle, with its hooked beak, feeds on sponges on coral reefs.
• The leatherback turtle, the largest sea turtle in the world, sometimes measuring over 2 meters in length and weighing more than 500 kg, comes to lay its eggs on certain isolated beaches, mainly between April and July.

Guadeloupe is an important nesting site for these migratory species, with the beaches of Marie-Galante and La Désirade hosting dozens of nests each year. Each species enjoys full legal protection. Scientific monitoring, tagging, and awareness programs are carried out by local associations.

The aim is to monitor population trends, identify nesting sites, and limit threats (poaching, plastic pollution, collisions with boats). Sea turtles play an important role in the dynamics of marine ecosystems, with green turtles in particular helping to maintain the quality of seagrass beds by preventing their excessive proliferation.

Seabirds

Coastal areas and isolated islands are home to several species of seabirds, including Pelecanus occidentalis (brown pelican), the Fregata magnificens (magnificent frigatebird), the Sula leucogaster (brown booby), and the Phaethon aethereus (red-billed tropicbird).

• The brown pelican, recognizable by its wingspan of over 2 meters and its beak equipped with an expandable pouch, generally nests on islets, building its nest in shrubs.
• Superb, elegant frigatebirds, with a wingspan of up to 2.3 meters, glide above coastal waters and catch fish or small seabirds in flight.
• Brown boobies are often seen on islets far from human activity, forming colonies of several dozen to several hundred individuals.
• Terns, recognizable by their two long tail feathers, nest in small colonies, mainly on cliffs or rocky islets, usually laying only one egg per clutch.

Some of these species benefit from nature reserves, such as La Désirade, which enable their protection, the study of their biology, and public awareness. Seabirds transport nutrients from the sea to the land through their phosphorus-rich droppings, contributing to the cycle of elements and fertilizing certain coastal areas.

Mangroves and herbariums

Mangroves, composed mainly of mangrove species such as Rhizophora mangle (red mangrove), Avicennia germinans (black mangrove), and Laguncularia racemosa (white mangrove), cover approximately 3,000 hectares in Guadeloupe. They are mainly found in sheltered areas, lagoons, estuaries, and shallow bays. The stilt roots of red mangroves, which can reach over 2 meters in height, form a complex network. They trap sediment, reduce wave force, and provide a refuge for many fish, crustacean, and mollusk larvae. This nursery function is crucial for the replenishment of fish stocks. The quality of the water, often enriched with organic matter, also favors the presence of juvenile shrimp and crabs.

Mangroves store significant amounts of carbon, helping to combat global warming. Traditional and sustainable harvesting of certain products (mangrove honey, crabs) is practiced in some areas, while protective measures prohibit their destruction without authorization.

Seagrass beds, mainly consisting of Thalassia testudinum (turtle grass) and Syringodium filiforme (cylindrical grass), grow in dense mats on sandy-muddy bottoms, between 1 and 10 meters deep. They cover several hundred hectares, especially in the sheltered lagoons of the leeward coast. Seagrass beds play a crucial role in limiting seabed erosion, trapping carbon, and providing a food source for green turtles and herbivorous fish. They are also home to Lobatus gigas (lambi), an iconic Caribbean mollusk, as well as sea cucumbers and diadem sea urchins. Seagrass beds are therefore essential for maintaining biodiversity, coastal productivity, and the stability of certain commercial species (fish, shellfish).

However, these environments remain fragile: uncontrolled anchoring, pollution, and trampling destroy the leaves and rhizomes, threatening their balance. Preservation measures (regulations, organized mooring areas, monitoring) and public awareness campaigns aim to ensure their sustainability.