Title: Seagrasses of the Virgin Islands
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Permanent Link: http://ufdc.ufl.edu/CA01300975/00001
 Material Information
Title: Seagrasses of the Virgin Islands
Physical Description: Book
Language: English
Creator: U.S. Virgin Islands
Publisher: U.S. Virgin Islands
Place of Publication: U.S. Virgin Islands
Publication Date: 2005
 Record Information
Bibliographic ID: CA01300975
Volume ID: VID00001
Source Institution: University of the Virgin Islands
Holding Location: University of the Virgin Islands
Rights Management: All rights reserved by the source institution and holding location.

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Seagrasses of the Virgin Islands


Seagrasses are flowering plants that live underwater. These
marine plants resemble the land species of grasses in that they
have long blade-like leaves. Seagrasses grow from a long
underground root called a rhizome. The leaves of the seagrass
grows up from the rhizome and the root clusters grow down from it.
Seagrasses are not to be confused with seaweeds. Seaweeds are
colonies of algae which attach themselves to the bottom substrate
by special structures called "hold fasts".
Seagrasses are found in shallow coastal environments around
the world. These areas resemble pastures on land with their thick
growth of seagrasses and algae. Seagrasses are unlike the majority
of marine plants in that they are true flowering plants. They
produce flowers and seeds annually. These plants produce a
significant amount of the oxygen generated in local inshore
waters.
The location of seagrass beds is controlled by a number of
factors, including the character and stability of the bottom,
depth, water clarity, currents and grazing by herbivores (plant-
eating animals). Seagrasses require a sandy bottom in areas with
calm seas to allow the seagrass roots to become firmly anchored to
the sea floor bottom. Since the grasses require a lot of light,
they usually do not grow below depths of 60 to 70 feet (20 to 23
meters).
There is usually a band of bare sand found between seagrass
beds and a coral reef. This is because the fish and sea urchins
that live on the reef graze on the grasses on this area, creating
the halo affect.
Of the 45 species of marine seagrasses which exist worldwide,
four species can be found in the Virgin Islands:
Shoal-grass (Halodule wrightii), is an early colonizer of
disturbed areas and usually grows in water too shallow for other
species. The leaves are narrow and flat in cross-section.


Shoal-grass










Turtle-grass (Thallassia testudinum), themost common of the
local grasses, characteristically has deeper root structures than
the other seagrasses. The leaves resemble ribbons and can grow
over a foot long.






II
Turtle-grass







Manatee-grass (Syringodium filliforme), can be recognized by
its round leaves when viewed in cross section.





Manatee-grass







Small turtle-grass (Halophila decipiens), has small, rounded
leaves, usually paired. This delicate looking species is found
deeper than other species.



Small turtle-grass






Seagrass beds are important in many different ways, yet
people would not consider them to be any more important than the
weeds that grow in their yards. Sea grass beds are valuable to our
coastal environment by:
maintaining water clarity by trapping fine sediments from
upland soil erosion,
stabilizing the seafloor which reduces beach erosion and
sediment stress to other marine habitats caused by storm waves.










providing important habitat for many fishes, crustaceans and
shellfish,
being a food source for many marine animals such as sea
turtles, conch and many fish, and
serving as nursery areas and providing refuge for many
species of fish and other marine life which are recreationally and
commercially valuable.

As residential and commercial development continues to reach
outward to coastal areas, our seagrass beds have become affected.
Dredging and filling projects, soil erosion and increased levels
of water pollution are all factors threatening the health of our
seagrass beds. Heated water discharges from industrial plants can
inhibit seagrass growth. Elevated salinity levels caused by the
discharge of saltwater from desalination plants can be harmful to
seagrass beds. Poisons and other pollutants cloud the water,
preventing the grasses from receiving the sunlight needed for
growth. Boaters can cause significant damage by anchoring and
boating in seagrass beds. Strong waves caused by storms can rip
the roots from the seafloor.

Without our coastal seagrass beds, local waters would remain
clouded with sediment, beaches and shoreline areas would be more
prone to erosion, coral reefs could become silted over by sand
constantly moving along the seafloor and a vital nursery habitat
for many species of marine life would be lost. Seagrasses
exemplify the interdependence of elements in the marine community.
In essence, the elimination of our seagrass beds could create a
"Domino Effect". This means that the removal of one key member of
any environment could ultimately lead to the demise of the
environment as a whole.










St. Thomas Seagrasses


1. Magens Bay
2. Thatch Cay (Eva Bay)
3. Water Bay
4. Smith (Lindquist) Bay
5. Sapphire Bay
6. Red Hook Bay
7. Great St. James
8. Great Bay
9. Cowpet Bay
10. Nazareth Bay
11. Benner Bay
12. Long Point to Bolongo Bay
13. Frenchmans Bay to Morningstar
14. Pacquereau Bay
15. East Gregerie Channel
16. Sprat Bay
17. Druif Bay
18. Lindberg Bay
19. John Brewers Bay
20. Perseverance Bay

Note: This does not show the locations of all seagrass areas
around St. Thomas. The areas shown are the largest and within the
depth range of most snorkelers.










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St. John Seagrasses


1. Frank Bay
2. Cruz Bay
3. Caneel Bay
4. Hawksnest Bay
5. Maho Bay
6. Francis Bay
7. Mary's Creek
8. Leinster Bay
9. Threadneedle Point
10. Brown Bay
11. Newfound Bay
12. Privateer Bay
13. Hansen Bay
14. Western Round Bay
15. Hurricane Hole (Borck, Princess, Water and Otter Creeks)

Note: This does not show the locations of all seagrass areas
around St. John. The areas shown are the largest and within the
depth range of most snorkelers.

















St. Croix Seaqrasses


1. Frederiksted (North of pier)
2. Butler Bay
3. Rust-Op-Twist
4. Salt River
5. Christiansted Harbor
6. Altona Lagoon
7. White Bay to Green Cay (Behind barrier reef system)
8. Buck Island
9. Green Cay to Cottongarden Bay (Behind barrier reef system)
10. Isaac Bay to Canegarden Bay (Behind barrier reef system)
11. Krause Lagoon
12. Manning Bay

Note: This does not show the locations of all seagrass areas
around St. Croix. The areas shown are the largest and within the
depth range of most snorkelers.










































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