Diversity of reef organisms
A healthy reef supports a rich diversity of organisms.  CLICK ON a "hot" button to see some examples of Caribbean reef plants and animals. Throughout the VIRTUAL DIVE we’ll see these and many other reef-dwellers and will study what they do, how they behave, and how they interact. hot buttons for diversity section of BIOLOGY OF CARIBBEAN CORAL REEFS website diversity of corals diversity of gorgonians diversity of sponges diversity of worms diversity of molluscs diversity of crustaceans diversity of echinoderms diversity of tunicates diversity of turtles diversity of fishes diversity of sharks/mammals
icon for mangrove-divresity section of BIOLOGY OF CARIBBEAN CORAL REEFS website

Plants: mangroves

The topic of plants is divided into a section on mangroves, presented here, and a section on SEAWEEDS & SEAGRASSES located elsewhere.

seahorse "dive leader" in BIOLOGY OF CARIBBEAN CORAL REEFS website photograph of mangrove trees taken from a video


"Mangroves are so commonplace around Caribbean islands that they may be overlooked by divers. Their extensive root systems trap sediments, improve water quality, and provide food and shelter for invertebrates, and nursery areas for fishes" - Bonaire 2003


Mangrove tree, such as red mangroves Rhizophora mangle, are salt-tolerant, and their shady canopies and permanently submerged roots create diverse habitats which support a rich community of plants and animals.  The multi-dimensional habitats created provide food and protection for the developing stages of many species of shrimps, crabs, and fishes

photo composite of red mangrove trees
The extensive root systems of mangroves decrease water flow, entrap sediments, and provide three-dimensional habitats for algae, fish, and invertebrates.
photo composite of mangrove flora and fauna
photo composite of algae, fishes amongst the buttress roots of mangroves
seahorse "dive leader" in BIOLOGY OF CARIBBEAN CORAL REEFS website photograph of buttress roots of mangroves taken from a video

"If we belly up to the edge of the mangroves, we see how the buttress roots create 3-dimensional habitats for algae, invertebrates, and fishes...Oh, this that a baby barracuda...Hmmm! Quite a little cutie!" - Bonaire 2003

NOTE although juvenile barracuda are common in mangrove areas along with juveniles of many other species, the fish seen by the dive leader might actually be an adult Harlequin bass (see photo directly above)

photograph showing aerial roots of a black mangrove tree
photograph showing buttress roots of red mangrove treesBy tolerating both salt water and buildup of anaerobic sediments, mangrove trees have tended to minimize contact with less-tolerant potential competitor trees and have thus enhanced their evolutionary success.

Buttress roots of red mangroves
have numerous pores or “lenticels”
which allow oxygen to diffuse in
when exposed to air. The pores are
hydrophobic; that is, they prevent
water entering when the tide rises


Aerial roots or “pneumatophores” of black-mangrove trees allow
oxygen to diffuse into the underground root system which may
be permanently buried in anaerobic muds. Thefringing reef of
Little Cayman Island is visible in the upper part of the photo

photograph of aerial roots of a black-mangrove tree
Mangrove trees have special tissues for secreting salts.  For this reason, their internal sap concentrations may be only 1-2% the salinity of the surrounding water. 





Extensive aerial-root system
of black-mangrove tree
Avicennia germinans

photo composite of a seedling or propagule on a black mangrove tree, and flowers on a red mangrove tree
Mangroves propagate by dropping seedlings which can float in the ocean for several weeks and be dispersed by water currents.  In many species the seedlings have an obligatory floating period ranging from 1-6 weeks before the roots will develop.






Black-mangrove seedling (“propagule”) attached to the parent tree 0.6X. 
Development to this stage may take up to 32 weeks.



Inset: flowers of a red-mangrove tree

photograph of mangrove seedlings growing vertically

Propagules of black-mangrove trees Avicennia germinans grow vertically, not a result of penetrating after falling, but rather a “verticalisation” caused by root growth

photograph of a young stage of mangrove growth, emphasising the land-reclamation ability of mangroves

Aggressive recruitment by mangroves leads to land reclamation

Let's get another viewpoint on the matter of a mangrove's propagation:

No. 1 of a cartoon series of 6 dealing with snails on mangroves No. 2 of a cartoon series of 6 dealing with snails on mangroves No. 3 of a cartoon series of 6 dealing with snails on mangroves
No. 4 of a cartoon series of 6 dealing with snails on mangroves No. 1 of a cartoon series of 6 dealing with snails on mangroves No. 1 of a cartoon series of 6 dealing with snails on mangroves
No. 1 of a cartoon series of 6 dealing with snails on mangroves

In the past 30 years, hundreds of thousands of hectares of mangroves, representing over 35% of the total, have been logged worldwide for firewood and charcoal production, or cleared for various types of coastal development including salt production, agriculture, and urban development.  Mariculture of fishes and prawns alone have accounted for over half of the losses of photograph of Caroni Swamp mangroves, Trinidadmangroves.  Naylor et al. 2000 Nature 405 (6790): 1017; Valiela et al. 2001 Bioscience 51: 807. 

NOTE a measure of land area in the metric system equivalent to 100 X 100 meters or about 2.5 acres



The Caroni Swamp, Trinidad has long
been home to flocks ofscarlet ibises

graph showing loss of mangrove-forested areas worldwide from 1980
Recent assessment of world mangrove-forest stocks suggests that about 20% of standing stock has been lost since 1980.  McCauley et al. 2015 Science 347 (6219): 247.

Commercial use of mangroves has a direct impact on the health of coral reefs.  The lists below show features of mangroves that are directly of value to reefs and directly of value to humans:


nursery for fishes
coastal protection
flood control
sediment trapping
water quality improvement
food and shelter for molluscs


production of paper
fish-culture ponds
shrimp-culture ponds
fishing materials
construction materials
fermented drink