A LOCAL WAY OF LEARNING
MISSING MANGROVE MESSAGE
Eulalie R. Rivera Elementary School
Environmental Education Team
In a pre-post study exercise, students will increase in their knowledge of basic
information on mangrove stands by a grade level as evidenced by sheet completed.
Used as an introduction to the mangrove ecosystems of the Virgin. Islands,
either in science or language class, this is a quick activity preceding an
actual or simulated investigation. In itself, it could also serve as a basic
information on the importance of mangroves.
1. Distribute the activity sheet, and allow 20 minutes for the first use.
2. Without discussion, have student place activity sheet aside (or collect
3. Discuss the details of the relevant portion of DCCA Fact Sheet No. 8, or
distribute copies to the students for self-study -10 minutes.
4. Direct students to re-do the activity, based on study, making corrections in
entries by writing new word or name choices directly above the original entries.
5. Score original and repeat activity responses. Words or names need not be in
specific order to be correct.
6. Discuss the value of mangrove stands to Virgin Islands environment.
Coastal Habitats: Mangroves, DCCA Environmental Fact Sheet No. 8.
MISSING MANGROVE MESSAGE
Read over the mangrove message, then go back, and from the list of words and
names, fill in the blanks. Note: some words are used several times. Put aside
this pre-study exercise and review the information on DCCA Fact Sheet No. 8. Do
the exercise again, changing your entries by writing the new words or names
directly above the original entry. Determine your score by the number of
original entries correct, and the second score by number of appropriate
corrections made after study.
Muddy or sandy
West End Salt Pond
Air and sunlight
Mangroves are flowering trees which can live
in salt or brackish water, as well as salty
mudflats near the shoreline. There are three
types of mangroves; red, black, white. Red
mangroves are perhaps the most distinctive,
having long prop roots that reach down in to
the water. These prop roots provide hiding
places for a wide variety of marine animals.
Mangrove prop roots also trap dead leaves,
sediment and fresh water that washes down
from the land with storm runoff. This helps
protect water quality offshore.
Mangroves require certain conditions for
establishment and sustenance and, in turn,
modify the environment in a characteristic
way which further favors their growth. Red
mangroves grow from a cylindrical seedling
which may float miles from the parent tree.
as these mature, the root end becomes heavier
so that it hangs downward with the future leaf
end sticking up. Eventually, the pod sinks.
when it does, it must encounter a muddy or
sandy bottom with sufficient nutrients.
the water must be shallow enough to allow the
seedling to reach air and sunlight. The water
Must be calm enough to allow seedling to take
root and grow. These requirement explain why
mangroves do not usually establish on windward
casts except where some shoreline features
offer the necessary protection and bottom
Eventually the leaves and sediments form new
muddy or sandy
west end salt pond
air and sunlight
thus mangroves are considered land builders.
once this new land is establish, the red
mangrove die off naturally and are succeeded
by black mangroves and eventually white ones
New red mangrove seedling will take root
along the outer edge of the new shoreline.
This sequence of succession creates a patter
of zonation in which the pioneer red mangrove
is at the water's edge black mangrove occupy
a zone behind and white are more inland,
but still in sand soil.
Mangrove forest frequently develop at the
mouths of streams and rivers. On larger
tropical island and main lands where these
occur, really spectacular mangrove estuaries
can be found. Although historical records
indicate that there used to be several
stream in the Virgin Island, none exist now
Therefore, local mangrove areas are not
estuaries in the usual sense except periodi-
cally when the guts which terminate in
mangrove bays discharge storm water.
The mangrove have a natural tendency to form
closed ponds or nearly enclosed lagoons. As
the plants grow out across shallow water,
they may eventually merge with other
mangrove or a headland on the other side of
a body of water. Soil may fill in to close
the pond off. If a sufficiently strong
channel of water runs through, soil will not
build up. The channel will reamin open
between the sea and the quieter bay or
Mangrove habitats are limited in the Virgin
Island, probably because of the lack of
rivers or stream. The largest areas which
did exist have been destroyed by filling for
land development (eg., Krause lagoon,
ST.Croix and mosquito bay, ST.Thomas).
However mangroves are still abundant and can
easily be seen at the following places: salt
river, Altona lagoon, great pond, west end
salt pond, manning bay, ST.Croix; coral,
leinster, and lameshur bay, ST.John; and
jersey bay (mangrove lagoon) ST.Thomas.
many salt ponds also have good mangrove
DCCA ENVIRONMENTAL FACT SHEET NO. 8
COASTAL HABITATS: MANGROVES
What Are They?
Mangroves are flowering trees which can live in salt or brackish water,
as well as salty mudflats near the shoreline. There are three types of
mangroves; red, black and white. Red mangroves are perhaps the most distinctive
having long prop roots that reach down into the water. These prop roots provide
hiding places for a wide variety of marine animals. Mangrove prop roots also
trap dead mangrove leave, condiment and French water that washes down from the
land with storm runoff. This helps protect water quality off shore.
Eventually the leaves and sediments form new soil, thus mangroves are
considered "land-builders". Once this new land is established, the red
mangroves die off naturally and are succeeded by black mangroves and eventually
white ones. New red mangrove seedlings will take root along the outer edge of
the new shoreline. This sequence of succession creates a pattern of zonation in
which the pioneer red mangrove is at the water's edge, black mangroves occupy a
zone behind and white mangroves are more inland, but still in sand soil.
Species trapped in the mangroves are juveniles or both adult and
juveniles, indicating that the fishes use the areas as nursery grounds. The
large numbers of fishes, birds, and other animals that live in a mangrove area
are dependent basically on the nutrients and vegetable matter produced from the
leaves of mangroves and sea grasses. This material is eaten by herbivorous and
omnivorous animals. Their excrement and the organic soup from the rotting of
other leaf litter provide nutrients for plankton (single-celled plants or larval
animals) and bacteria. These, in turn, are eaten by larger animals, including
those harvested by man. Thus, mangrove areas play a very important part in the
food chain for marine life.
Major Attributes Use Limitations
Mangrove lagoons are quiet protected areas Cutting or removal of mangroves for
which provide safety for small boats development should be avoided as should
(hurricane holes). dredging and filling activities.
Important role in energy and food Hunting of birds and taking of eggs should
production. be discouraged. Fishing should have size
and catch limits.
Wide variety of habitats (ea,. mangrove Because water circulation is restricted,
forest, bare sand, muddy areas, grass beds, live board boats and motorboats are
and often coral reefs). discouraged.
Large and diverse populations of wildlife, Discharge of wastes of any kind is
particularly birds and marine life. undesirable.
"Land-builders" Development of adjacent areas should leave
a buffer of land to reduce runoff,erosion,
water pollution, noise, and other adverse
impacts on the mangroves.
Protect the quality of coastal waters from
fresh water and sediment runoff.
Red mangroves growing at the edge of a quiet shallow lagoon. Black mangroves on higher wet soil,
white mangroves on drier inland soil. Red mangrove prop roots trap sediment, support and shelter organisms,
extend shore. Litter contributes organic matter to water and sediments. Lagoonal grass and algae provide
oxygen, food, shelter for other organisms. Nurseries for juvenile reef and pelagic fish.
Island Resources Foundation, V. I. Marine Environment, (VICZM Program, Tech.
Supplement No. 1, 1976). Editor: Marsha McLaughlin,
Policy and Planning Unit, DCCA. Further info.: Environmental Specialist, DCZM.