Mariners enjoying many of the most popular bays in St. John may now secure their vessels to moorings as an alternative to anchoring. This extensive (and expensive) project was funded by philanthropist, Donald Sussman, in conjunction with the Friends of the National Park and the Virgin Islands National Park. The purpose of the program is the preservation, protection, and hopefully, the revitalization of the sea grass beds that lie on the bottom of these bays. What is the nature of sea grass? Why is it so important? How is it endangered and what can we do about it?

Local sea grass species include shoal grass, turtle grass and manatee grass. These underwater grasses are commonly found on the sandy bottoms of calm bays and between coral reefs. They reproduce and grow by means of an underground root called a rhizome, which lies down horizontally just beneath the sand. From this rhizome the blades of grass grow up and the roots grow down, forming a mat of root fibers that hold the sea grass to the ocean floor. Sea grass is dependent on sunlight and therefore, cannot tolerate cloudy water for extended periods of time.

Sea grasses control erosion by holding down loose sandy soils with their mat of roots, thus protecting our beautiful beaches. Moreover, they help prevent turbidity, or water cloudiness. This is an important function because cloudy water blocks out sunlight. One organism that is extremely sensitive to turbidity is the coral polyp, which is the building block of the coral reef. Although coral polyps are animals, most of their energy comes from a symbiotic relationship with algae that live within the cup-shaped opening of the polyp. Because algae are plants, they will die without adequate sunlight. Without the symbiotic algae, the coral polyp cannot survive, and without the coral polyp there can be no coral reef community.

Sea grasses control turbidity by trapping sediments washed down from land during rains and ultimately incorporating them into a seabed soil that is held securely by the sea grass roots. The blades of grass also slow down bottom currents and keep loose sediments from getting churned up.

Sea grass beds support a great deal of marine life. They provide nutrition for the green turtle and queen conch, and serve as a habitat for many species of juvenile fish and other sea creatures that are small enough to hide between the blades of grass.

Although not quite as sensitive as corals, sea grasses are also threatened by turbidity. They are currently in grave danger from the exponential increase in residential and commercial development on St. John. The prime turbidity-causing culprit is the failure to pave roads. Other enemies of clear water include unprotected and irresponsible excavation, especially on steep slopes, and improper sewage treatment.

A more immediate threat to sea grass comes from the proliferation of boat anchoring. The act of setting down and then pulling up an anchor tears the sea grass up by the roots and destroys the rhizomes, making recovery slow and difficult. Worse yet, when anchors are set improperly, they may drag, causing widespread damage that often includes injury to nearby coral reefs. Moreover, as an anchored boat swings around in the wind, the anchor chain is dragged over the sea floor in an arc, destroying all the grass in its path.

Years ago, harbors such as Caneel, Maho and Francis Bays had extensive sea grass cover. In those days literally hundreds of conch ambled slowly through the sea grass leaves at the bottom of the bays. With the advent of modern tourism and the great increase in the number of boats anchoring in these picturesque and well-protected harbors, the sea grass has all but disappeared and the conch population has plummeted.

The current mooring program is a powerful step towards the preservation of sea grass and coral reefs. Unlike anchors, moorings are relatively permanent fixtures. This minimizes the disruption of the seabed. Moreover, moorings do not depend on heavy chains lying on the sea bottom for a secure bite, nor are they are subject to dragging.

Hopefully, in addition to the mooring project, future development of St. John will be conducted in an environmentally responsible manner, keeping the bays as clear and as free from turbidity as possible.

Sea grasses tend to be resilient. If the stresses to their survival can be eliminated before it is too late, there is an excellent possibility that our once extensive fields of underwater grasslands will recover fully and will flourish as they did in the past.

Top of Page