Corals in Vieques

Go Snorkeling!

Take the opportunity to show your children the beautiful underwater corals. There are only 20% of the corals left in the Caribbean that were here 50 years ago! Going.. going .... soon gone.

Corals belong to the animal kingdom, and are members of the same group of animals as jellyfish and sea anemones (Phylum: Cnidaria). The actual coral animal or 'polyp' is soft bodied, with tentacles like a sea anemone. The main difference is that corals secrete an external calcium carbonate skeleton and sea anemones do not. This hard skeleton forms the framework of coral reefs. The tiny coral polyps occupy little cups or corallites in the massive skeleton. Corals can be colonial or solitary and there are several hundred species, some are large and branching and grow rapidly at a rate of up to 10cm per year, while others are mound shaped, growing slowly at only 1cm per year.

In addition to the hard corals, there are a variety of soft corals like this common sea fan (Gorgonia ventalina). The calcium carbonate skeleton of soft corals is located within their bodies, allowing them to move with the wave action. Sea fans typically grow so that the wave action is moving over the broad plane of their bodies, so all of the sea fans in an area will be oriented in the same direction.

Reef building corals live in symbiotic association with zooxanthellae, single celled algae, which live in the tissue of the corals. The zooxanthellae produce the oxygen, that the corals need to survive, by photosynthesis; in return the algae are protected from grazing species and can access the nutrients that the coral excretes - a mutually beneficial association.

Corals feed on zooplankton with the use of their tentacles. During daylight they mostly remain within their protective skeleton to avoid predation, but at night the tentacles are extended to allow them to feed.

Coral colonies grow by having the polyps bud off new polyps asexually. New colonies are established by the fragmentation of skeletal pieces or through the settling of planktonic coral lava on a hard substrate. The lava are the result of sexual reproduction.

What do corals need to grow? There are six major factors that limit coral reef development; water temperature and salinity, depth, light, sedimentation and emergence into air.

•  Coral reefs are only found between about 30 degrees north and south of the equator, where the water temperature is at least 70 degrees F, and optimal reef development occurs in waters where the mean annual temperatures are around 75 degrees F.

• Corals are intolerant of salinities that deviate significantly from that of seawater and gaps will occur in reefs where, for example, freshwater from a river enters the sea.

• Depth is also critical, coral reefs will not develop in water that is deeper than about 50-70m, and they grow most energetically at depths of 25m or less. Light, which is related to depth of water, is necessary for the zooxanthellae to photosynthesize. Without light the photosynthetic rate is reduced and with it the corals ability to secrete calcium carbonate.

• Corals also require clear water - sediment clogs their feeding structures and smothers them. For this reason corals usually grow most actively in areas of strong wave action, such as the windward side of a reef, where sediment is prevented from settling on the colonies.

• Finally corals reefs are limited in an upward direction by emergence into air. Most corals are killed by long exposure to air and so their upward growth is limited to the level of the lowest tides.

Global Coral Reef Monitoring Network

Demand for seafood is so great in the Caribbean that many reefs are severely over fished, throwing off the delicate balance essential to the survival of the reef ecosystem. Too many nutrients and not enough plant-eating fish cause algae to overgrow and smother corals.

How can we help our coral reefs?

Plant vegetation barriers along rivers and shorelines to reduce runoff.

• Force government agencies to establish moorings for boats to pick up and tie to, instead of damaging corals with their anchors.

• Pick up trash along beaches and in other coastal areas.

• Refrain from buying souvenirs, jewelry, or ornaments made of coral.

• Snorkel, dive, and anchor with care so as not to crush reef organisms.

• Buy only captive-bred aquarium fish

• Request seafood that have been sustainably harvested. Eat less seafood.

• Support education and research on coral reefs as well as reef-friendly legislation.

--A new study paints a grim picture of the health of coral reefs across the Caribbean. In the past three decades, the amount of coral cover has dropped about 80 percent, according to researchers in the journal Science. A team of U.K. scientists compiled data from 263 separate reef sites in the Caribbean for this week's report, which they called the most extensive coral study ever of the region.

Some of the causes are natural, such as disease and weather damage. Hurricanes, for example, can break coral tissue, making it more susceptible to diseases.
But much of the problem can be traced to humans. "The man-made causes, the ones we can do something about, need to be taken extremely seriously,"
"A lot of the important causes come from things people are doing on land, like pollution, sedimentation resulting from development and deforestation. They have very serioust repercussions".