University of Queensland Marine Science visit to Lady Elliot Island
Hobart and William Smith Queensland Term 1996
1. Background Information
Lady Elliot Island is a 100-acre coral cay on the southern tip of the Great Barrier Reef. It lies just within the southern boundary of the designated World Heritage area in this map of the Great Barrier Reef:
After taking and early morning bus from Brisbane north up the coast to Bundaberg, we boarded 15 seat planes for the 35 minute flight to Lady Elliot Island. Kathy Townsend, a doctoral student in the UQ school of Marine Science lectured and helped with student projects on the trip.
Lady Elliot Island is the only coral cay in the Great Barrier Reef with its own airstrip. The airstrip runs the entire diameter of the island (and gave our plane at least 20 meters leeway on landing). Lady Elliot is fringed on all sides by coral.
Excerpt from Student Journal:
Arrived on Monday, November 4, 1996. The weather was good, a bit cloudy, but a nice temperature. We had lunch, then went snorkeling! I saw: lots of fish, blue sea stars, coral (soft and hard), sponges, sea
cucumbers, and giant clams. After dinner I went on a walk along the beach and saw... a green sea turtle... laying eggs!
Though marine ecology was the focus of the trip, a lecture by Dr. Alan Cribb (retired botanist from the University of Queensland) included a description of the terrestrial vegetation typical on a coral cay. There are usually three main vegetation zones present on a small coral cay. The first is grass and herb zone. It is the least fertile and is the pioneer zone which abuts the beach front and is stabilized by plants such spinifex and bird's beak grass.
The shrub and tree zone is dominated by the screw pine (Pandaneus tectorius) and the coastal she-oak (Casuarina equisetfolia) whose nitrogen-fixing ability gives it a decided advantage.
The third zone is dominated by Pisonia grandis, large soft-wood trees up to 20 m in height. Here the black noddies nest in dense groups. There is a tendency for each zone to expand seawards over time.
Lady Elliot has a shallow inner reef extending out 300 meters from the shoreline. At this point there is a narrow rubble crest of 30 meters or so and beyond that deeper water coral gardens and the Pacific. The shallow inner reef and easily accessible deeper water made it an ideal instructional laboratory.
Three different species of branching coral compete for space in the reef flat. The corals' color comes from the symbiotic single-celled plants called zooxanthellae which lives within its tissue.
2. Plant and Animal Life
Among the most conspicuous invertebrates on the reef are the echinoderms (from the Greek for "spiny skin") such as the starfish (or sea stars) and the sea urchins. The most prominent of the starfish (asteroidea) are the bright blue Linckia laevigata which are quite common in the reef flat.
Somewhat less common, though by no means rare, are the mustard-yellow starfish Nardoa novacaledoniae which are also found in the reef flat.
Holothurians are called "sea cucumbers in part because of their widespread use in Asia as a base for soups. One of the most common species on the reef flat at Lady Elliot is the sea cucumber Holothuria leucospilota. In some areas, the reef can seem to be covered by these or other holothurians. Most species feed on the rich organic film that covers sandy surfaces.
A second type of sea cucumber, less common at Lady Elliot, is Bohadschia argus. "Sea Cucumber"
This common sea urchin, Echinometra mathaei, has simple spines with white tips and is usually found in holes bored in coral.
Hiding in crevices, the spectacular Heterocentrotus mammillatus, or slate pencil urchin, with its many flattened spines was only occasionally seen in the reef flat. They may be up to 200 mm in diameter.
This particular urchin, Diadema savignyi, hides under rocks or coral during the day but is active at night and was seen during the night snorkeling. It has poisonous spines.
Chitons are an ancient group of molluscs that usually graze on algae. In the Great Barrier Reef, they are often found in intertidal pools or under rocks at the shore's edge.
Butterflyfishes are known for their beautiful color patterns and graceful appearance. Many feed on live corals.
In parrotfish, all teeth are fused to form a distinctive beak-like structure. They consume considerable amounts of coral rock while feeding. It is ground to a fine powder by special teeth in the throat and voided with the feces. Individuals are capable of female to male sex change.
The manta ray can grow to 7 m across and weigh over 3 tons. It has a black dorsal surface and white underneath with large cephalic flaps on either side of the head. It feeds entirely on plankton and small fish. Other rays seen at Lady Elliot included the shovelnose and the blue-spotted rays. Additional information on manta rays
Carapace: 70 to 110 cm. Less abundant that the green turtle, the loggerhead turtle breeds and nests along the Bundaberg coast, including Lady Elliot Island. They feed on crabs and shellfish. The population in Queensland has declined by about 50 percent in the last decade
Carapace: 40 to 120 cm and highly domed. Green turtles are relatively common. They feed on seagrass and algae and breed in rookeries including Lady Elliot Island. They are more common at Heron Island.
Lady Elliot is a breeding ground for the endangered red-tailed tropic bird. Females usually produce a clutch of one egg (rarely two) which are incubated by both parents for about 40 days. Young are fed with fish from their parents' bills for a period of two to three months. In recent years, only one or two pairs have nested on LEI
Both the pied and the sooty oystercatchers were common on the shore at Lady Elliot.
The white-capped noddy is one of the world's most numerous species as anyone who has visited Lady Elliot can attest. The nest shown here is quite typical: a platform of leaves on a branch of a Pisonia or Pandanus tree. A clutch usually consists of a single egg. Their diet consists of anchovies, hardyheads, squid, and krill and the they may hunt in flocks containing up to 3000 birds.
3. Field Projects
Before starting field projects, Professor Tibbetts of the UQ School of Marine Science led a day reefwalk to orient students to the fauna of the inner reef including holothuroidea (sea cucumbers), echinoidea (sea urchins), asteroidea (starfish), mollusks, corals, fish, small sharks, blue-spotted rays, and octopi. The contrast with Stradbroke was obvious.
Additional items seen on the reef walk were brittle stars, cone shells (Conus ebraues), and chitons which are found on the rubble shore.
Day snorkeling beyond the reef crest provided an orientation to the fauna of the outer reef, including black-tipped and white-tipped sharks, manta and eagle rays, green and loggerhead turtles, coral cod, sweetlips, tang, wrasse, parrot-fish, damsel-fish, butterfly-fish, angel-fish, flute-mouths, cleaner-fish, and moray eels.
Snorkeling at dusk in the inner reef flat illustrated the "changing of the guard" as the more colorful fish active in the day went into hiding and the silver and "transparent" fish started their nighttime feeding. There is even a switch over in the activity of sea urchins as Diadema savignyi (shown here) with its long spines becomes increasingly active.
Mike Conn '97, Rebecca Price '97, and Todd Pauliny '97 report on a project involving crab behavior. Groups reported on the projects they completed at Lady Elliot, many of which involved a comparison study at Stradbroke Island. Topics included
Species competition and partitioning of resources were themes of the lectures at Lady Elliot. Here two species of coral compete for space in the reef flat with a giant clam.
Not all relationships on the reef flat are competitive. The dinoflagellate zooxanthellae and coral or clams are symbionts. The mantle of this clam Tridacna crocea is colored by enclosed zooxanthellae. The green and brown corals are also colored by their symbiotic zooxanthellae. The corals depend on the photosynthetic activity of the zooxanthellae as a source of carbohydrates. The zooxanthellae obtains protection from the coral.
4. Links to Related Sites
Other Field Sites for HWS Queensland Term
Information on The Great BArrier Reef Marine Park Authority
The Great Barrier Reef Marine Park Authority
Information on Marine Organisms