Reef Madness

By Ryan Kaszynski

April 4th and 5^th

Monday was our first full day on Heron Island. After breakfast Derek gave us a rundown of the myriad number of marine animals that can kill you, ranging from the nervous system debilitating poison of the cone snails to the instant and severe pain of the Box Jellyfish sting. After the lecture the group broke away from our morning teatime to walk the beach with Derek. By way of the Pisonia forest we arrived at shark bay beach, where sharks, rays, and an occasional turtle cruise by in the shallows. Heron Island, Derek told us, is bisected by the tropic of Capricorn, which means on our short walk across the island we had crossed from a Subtropical classification to Tropical classification. The area of land in these two classifications is constantly changing, due to the oscillating landmass of the Coral Cays. The sediment buildup that occurs between the shore and the reef wall eventually forms a new beach, while the other side of the island erodes away. The resort, which shares the island with our research station, had to construct seawalls to slow the pace of erosion to preserve its buildings.

Several species developed unique relationships to overcome the low nutrient soil and high competition of reef life. We learned how the white hooded noddy nests in the branches of the Pisonia tree, whose seed burrs stick into the feathers of the noddy. The seed laden bird flies from island to island and eventually is tangled with too many burrs to fly.  The decaying body of the noddy provides the necessary nutrients for the Pisonia to grow, which in turn makes more nesting space for the noddies. On the reef, we learned about a symbiotic relationship between a gobbie and a shrimp. The shrimp, which has poor vision, digs a burrow while his housemate, the gobbie, keeps watch with keen eyesight. The shrimp keeps one antennae on the gobie at all times so he can hide from preditors.

All these species depend on the energy created by the photosynthetic algae zooxanthellae in coral tissue. When the coral is stressed, it expels the zooxanthellae and turns white. The symbiotic relationship between coral and algae, which is the primary producer of the ecosystem, underpins all animal life on the reef. Coral only grows at a rate of 7 meters vertically every 1000 years, which means that the pace of sea elevation due to global warming will soon outstrip the growth of coral. Sunlight will have difficulty penetrating the surface to reach the zooxanthellae, and the coral will die. Indonesia and Papua New Guinea boast 500 to 600 distinct species of coral, while the Great Barrier Reef only contains 300 distinct species of coral.

Flora and fauna have hurdles beyond the geographic isolation of an island. Derek picked up a monkey-puzzle nut, which thrives in a mangrove environment. “Just because a species can get to the Island,” Derek told us, “doesn’t mean it can survive there.” We witnessed the struggle for survival firsthand when our group came across a baby turtle making its way towards the ocean in the light of day. We all cheered as the baby turtle slipped into the water and swam out to sea. One of the screaming gulls scanning the shallows spotted him, however, and in a moment of horror, plucked his body from the water and carried him off inland. Our piece of mind was rattled again later that day by the sound of baby turtles smashing into the kitchen roof.

After an introspective lunch, we laboriously pulled on our blue, full body, skintight sting proof suits and took to the water to collect data for our projects. Despite the lack of a full range of motion, we went about collecting data on Sea Star population density. In our presentation that evening, we explained how the Blue Sea Star, of the family Linkea, has the unique ability to asexually reproduce by splitting away from an arm. While other starfish, such as the brown sea star (family Naroa), have the ability to regenerate lost arms, a disembodied arm of the Blue Sea Star has the unique ability to generate a new body disk. One presentation examined sea cucumbers, and another examined populations of various classifications of coral, such as branching, digitated, massive, soft, solitary, and plate.

 On Tuesday we said our goodbyes to Derek. Tim Stevens, our new professor, began his afternoon lecture explaining Australia’s Exclusive Economic Zone, which encompasses a vast amount of ocean territory ranging from -10 to -50 degrees longitude. Tim told us that the reefs we have today originally came from low-lying hills. As the ocean rose and flooded these areas coral began to form and decay, accumulating as sand after passing through the gut of the parrotfish. This sand elevated the flooded area until it became a beach. Because coral have had to adapt to sun exposure, a common ingredient in UV sun block is derived from coral mucus. However, too much exposure to elevated water temperatures or abnormal amounts of fresh water can lead to coral bleaching. Bleached coral can be examined on a 1-6 scale, which depicts 1 as ghostly white and 6 as dark in color. Coral growth is hindered by farming runoff, which gets washed into the ocean in the wet season and circulates among coral populations via the South Pacific Gyre.

The North pacific Gyre, South Pacific Gyre, North Atlantic Gyre, South Atlantic Gyre, Indian Gyre, and Antarctic current make up the general flow of water in the earth’s oceans.  Southern humpback whales travel on the Antarctic current to birthing grounds in the Great Australian Bight, then south to the feeding grounds off Antarctica. Many sea turtles use these gyres to travel great distances from their birth beach to their feeding area and back. Due to high mortality rates, fishing rigs were required to use what fishermen call the Deck Hand Elimination Device, a metal chute that diverts turtles away from the catch. Because coral reefs are so biologically diverse, the practice of purse netting and other unselective fishing techniques has had disastrous effects on the ecosystem. Between climate change, runoff, and overfishing, humans are overwhelmingly contributing to the decimation of the coral reefs.