Closed triopical rain forests on the islands of Halong bay make up an ecosystem that is evergreen and humid. It features a richness of plant species (over 1000 species in total). The plant populations are various.
The include mangrove species; plant species on sandy island coaslines; plant species on mountain slopes and cliffs; plant species growing on mountain tops, at cave entrances and slots. Researchers of the World Nature Conservation Society have discovered seven endemic plant species of Halong bay. These seven endemic species live only on limestone islands here but not elsewhere in the World. The are Ha Long cycas revoluta, "Kho cu dai tim", Halong palm, "Kho cu dai nhung" plant, ''Mong Tai Ha Long'' plant, Halong cortex acanthopanacis radicis and the ''Ha ve nu hoa vang' plant. But other documents say that Ha Long has as many as 14 endemic plant types, of which are those discovered and named by the French in honor of the Ha Long locality, for example Ha Long jasmine, Ha Long fig tree, "phat du nui", Ha Long "song be" tree, Ha Long orchids etc. In fact, no comprehensive research on the plants on all the islands and adjacent areas of Halong bay has been carried out. Therefore, the lis of endemic plant species in Halong bay may be expanded. Scientists recently discoverd on some islands of Ha Long bay the species ''Phyllostachys bamboo growing inversely''. While other Phyllostachys bamboo types point their tops toward the sky, ''Phyllostachys bamboo growing inversely'' points the top down to the ground.
According to statistics, the ecosystem of tropical evergreen humid closed rain forests in Halong Bay and Bai Tu Long Bay has 477 magnolia species, 12 fern species and 20 mangrove species. There are four amphibian species, 10 reptile species, 40 bird species and 14 animal species. There is a type of petty monkey (with a smal body) that is raised by special methods on Khi Island (Monkey Island). The Ecosystem of sea and coaline is mostly composed of green vegetation growing on limestone islands.In Ha Long, this ecosystem includes the withland sub-ecosystem and the sub-ecosystem with their specific traits
- Wetland sub-ecosystem: This is the tidal and mangrove ecology in Halong bay, including 20 species of mangrove plants. The witland sub-ecosystem of Ha Long is also home to 169 species of polychaete worms, 91 species of seaweed, 20 species of bird, 10 species of reptile and six species of other animals. The ecological type of ''hard seabed and coral reefs" is mostly located in the Hang Trai, Cong Do and Van Gio areas. 232 species of coral have been found here. The part of the hard seabed and coral reefs are home to 81 species of gastropods, 130 bivalve species, 55 species of polychaete worms and 57 crab species. The sub-ecosystem of cave, grottos and island lakes in Halong Bay is very unique and rarely found elswhere. The Tung Ngon area is a particular habitat for 65 species of coral, 40 species of animals living on the seabed and 18 species of seaweed. Here there are also four rare animal species recorded in the VietNam Red Book. The ecological type of ''soft seabed'' is the habitat of five species of seagrass, 140 species of seaweed, three polychaete worm species, 29 mollusk species and nine crustacean species. Ther is the ecology of ''tidal grounds without mangrove forests'' where mainly live species of bivalve mollusk and highly nutritional marine worms such as sipunculida, stichopus japonicus selenka and meretrix meretrix L.
- Sea sub-ecosystem: There are 185 species of phytoplankton plants in Halong Bay. There are 140 species of phytoplankton plants animals in the whole HaLong-Cat Ba area. There are 500 species of ''seabed'' animals, of which are 300 mollusk species, 200 polychaete species and 13 echinoderms species. There are 326 species of self-traveling animals in Ha Long Bay
Scientists evaluate that there are now about 347 plant species in Ha Long Bay, 16 species of which are endangerd or will be endangered; they are listed in the Viet Nam Red Book. Among rare plants are 95 herb species, 37 bonsai species, 13 fruit tree species and 10 plant groups able to be used for different purposes.
Invertebrate species are diversified on islands of Ha Long Bay, especially those living in rocky hollows. There are 60 endemic animal species. In Ha Long are raised kinds of haliotidae sea snails, sea cucumber, sipunculida, shrimp, fish, and several kinds of squid, octopus, oysters and abalone. According to data of the Ha Phong Oceanographic Institute among 1,151 animal species in Ha Long Bay there are nearly 500 fish species and 57 crab species. The are a rich source of animals of high economic value to be preserved and multiplied.
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