St Eustatius National Marine Park

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Chapter 3. SITE DESCRIPTION

a - General features of the site

Terrestrial surface under sovereignty, excluding wetlands:

2 sq. km

Wetland surface:

0 ha

Marine surface:

27 sq. km

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The St. Eustatius marine park surrounds the entire island of St. Eustatius, extending  from the shore to the 30 m depth line, covering a total area of 27 km2. It inlcudes diverse coral reef, gorgonian reefs, seagrass, macro-algal beds, rubble and sandy bottom and rocky intertidal habitats. A zoning plan divides the park between recreational (diving) and commercial uses, inlcuding two fish reserves, and a designated anchoring zone for large ships, with a system of permanent mooring buoys in the recreational zones to facilitate diving and prevent anchoring damage to the corals.

Zeelandia beach is the index beach for nesting turtles. It is the only place where all three species (Leatherback, Green and Hawksbill) nest regularly. The beach is 1.4 km long, the width varies year to year depending upon sand accretion and depletion. Beaches on Statia have black sand which is made up from titanium and iron weathered from the volcanic rocks (Ippel, 2000). White sandy sections on Zeelandia beach are derived from sandstone between the two hilly sections north and south of the island. This is the only terrestrial surface included in the Marine Park. There are no wetlands on St Eustatius.

b - Physical features

Brief description of the main physical characteristics in the area:

St. Eustatius lies at the north end of a continuous submarine bank, no deeper than 180m, that also contains the islands of St. Kitts and Nevis. The Marine Park varies in width between 1 and 3 kilometers. The monthly average sea surface temperature ranges from 25°C in January-March to 29°C in August-November. Visibility ranges from 15m to 30+m. There are usually two high tides and two low tides every day in St Eustatius, with about six hours between high tide and low tide. The average tidal range is around 45cm. The water has a constant salinity and is low in naturally occurring nutrients. The sea bottom is comprised of a mixture of biologically fixed silica and calcium carbonate, as well as clays, silts, and sand sediments.

Geology:

Morphologically the island consists of two major components, the Quill stratovolcano and the Northern Centers. The former, which comprises the southern two-thirds of the island, is a young symmetrical, open crater cone built almost entirely by deposition of pyroclastic deposits from numerous eruptions. The latter is an older complex of Pelean domes, lava flows, and explosion craters. These structures continue underwater with lava flows covered by coral

Soil:

n/a

Topography:

n/a

Bathymetry:

The submarine contours around St. Eustatius reveal that the Northern Centers lie in the middle of a circular submarine bank with the Quill positioned on the southeast margin (Fig. 30). The dominant tectonic trends (NE-SW and NW-SE) characteristic of the Lesser Antilles are also present on St. Eustatius. The northwest-southeast direction is exemplified by the elongation of the island itself, whereas the northeast-southwest direction is well shown by the extension, as defined by the 50 m submarine contour, on both sides of the island. The same structural direction is indicated by indentations in the 50 meter submarine contour on opposite sides of the submarine bank suggesting a northeast-southwest fault may cut through the bank between St. Eustatius and St. Kitts.

Volcanic formations:

See Geology

Sand dunes:

n/a

Underwater formations:

The sea bottom of the Marine Park is primarily a shallow sloping sandy plateau covered with seagrass beds and many shipwrecks. There are a variety of reef types on St. Eustatius, from shallow sloping reefs to patch reefs through volcanic boulders of various sizes to spur and groove type reefs with sandy channels divided by lava fingers. Each of these offer a hard substrate for coral and other animals to settle on.