Cays, Beaches, Tidal Pools
Andros Island, Bahamas
Amanda Brandner, Catherine Brooke, Leslie Wade
The two pictures above show the contrast of the geology of the cays. The rocky coastline is always located on the east side. The sandy side without rocks is always located on the west side of the cay. This can be contributed to the direction of the current flow. The tide always flows from east to west. This causes the rocks on the east side to form a protective barrier for the sand and flora of the island. Meanwhile, the west side of the island has a smooth and sandy appearance, lacking rocky features, because the tide doesn't flow directly into this side of the island. An interesting fact is that the sand on the west side is not made of silica but rather of calcium carbonate from the limestone and coral.
An interesting characteristic that can be noted about Andros is the number of blue holes found throughout the island. All of the blue holes of Andros, terrestrial and oceanic, are caused by fault line or fracture. "These deep caves are usually associated with localized faulting. The systems generally run parallel to a deep-water offshore canyons such as the Tongue of the Ocean east of Andros Island. . ."
These oceanic blue holes are always found off the east coast and sometimes connected to the inland terrestrial blue holes by a system of underwater caves and caverns.; We had the opportunity to enjoy a freshwater swim in two of the inland blue holes of Andros. We visited Uncle Charlie's Blue Hole early in the week, but the class favorite was definitely Church's Blue Hole. Church's is an enormous hole, the largest on the island, and the fun part was the 16 foot "jump" from the top into the water. The class also visited two oceanic blue holes, one at Conch Sound and the other at Rat Cay. There was an abundance of Atlantic spadefish at Conch Sound, but the murky water made the viewing of any other species that may have been patrolling the premises difficult. ;The trip to Rat Cay proved to be more exciting, due mainly to the abundance of different species lurking about. We were able to see Southern stingrays, French angelfish, carpet anemone, various types of coral, French grunt, Blue-headed wrasse, Blue tang , and most exciting, Nurse sharks!
PHYLUM: Echinodermata FAMILY: Oreasteridae
This cushion star is a wonderful example of the innumerable beautiful life-forms found offshore of the many cays of Andros Island. A cay can best be defined as a small, flat island. The cays of Andros are made up of coral and limestone, the principal type of rock found on the island.
Note: The organisms classified in the phylum Echinodermata all share a unique water vascular system, "a hydraulic network terminating in a large series of tube feet which can be extended or contracted by varying the water pressure. These tube feet often bear a minute terminal sucker by means of which the animal can hold onto hard surfaces and even crawl about." (Voss 124)
These crabs are interesting because only the massive claws are harvested for eating, and the crabs soon grow new claws.
SEA CUCUMBER (unidentified species)
- notice the many tube feet located on the ventral side. The cucumber utilizes these feet for movement. If the cucumber feels threatened or endangered, or if placed in warm water, the creature has the capacity to disembowel its internal organs (a.k.a guts) and then regenerate a completely new set of organs.
The stars get their name from the frailness of their arms. Sometimes when handled, the arms will break off.
LIVE KEYHOLE SAND DOLLAR
We found many 'dead' sand dollars, which are stark white in appearance, and were able to bring them home. However, the one pictured is a live sand dollar. They can range in color, from sand colored to light brown, and sometimes even gray. Sand dollars are found in sandy, shallow areas.
SEA ANEMONEPHYLUM: Cnidaria CLASS: Anthozoa ORDER: Actiniaria
Sea anemones are sessile organisms that embody tentacles encircling their mouths. The tentacles are armored with stinging cells which project poisonous nematocysts. When the anemones are threatened, they use nematocysts for defense to kill larger animals. Anemones also have the unique ability to sieve other organisms from seawater with their tentacles.
The tunicate is the most primal form of all vertebrates because it only contains four basic characteristics: hollow dorsal nerve chord, pharyngeal gill slits, notochord, and a separate mouth and anus.