Garie Beach

what really is destroying the great barrier reef?

PLEASE NO GLOBAL WARMING SPECULATIONS!: the great barrier reef began to get sick so long ago that it would not be sensible to attribute its demise to global warming or even the holes in the ozone layer. so, without the GW rap, 1. what factors are killing off what part of the ecosystem of the great barrier reef? i.e., what TYPES of coral are dying and why? what types of coral are not dying and why? 2. what is the cause of so many jellyfish beginning to populate the reefs, particularly deadly box jellies? 3. why has the population of the starfish called the crown of thorns grown so much? 4. what has "bleached" the corals of the reef? why? 5. what can be done to save the great barrier reef (which, btw, stretches all the way to tahiti!)? 6. if it dies off, what will happen to the waters off of northern australia--what types of life will live in them and why? 7. any other comments? no GW please!!!

Public Comments

1. I believe sedimentation and pollution are the main reasons along with global warming. minor temperature change and other environmental impacts are enough to break the symbiotic relationship between coral and their microbes. As for the other information... I'll let you figure that out on your own. This is too important of a topic for me to just give you a free ride ;)
2. Well gee, you are really tying my hands here, since, despite your insistence that GW is not involved, it certainly is playing a very important role in it these days. However, some other factors are these: Chemical PH change caused by pollution, fertilizer runoff and silt, Overfishing, which removes only certain species of fish, leaving a hole in the food chain, leading to gaps in the ecology. Plankton species die off. People think of "plankton" as a homogenous group of little critters, but they are the basic biology of the ocean. Whole species in the plankton ecology are going extinct, including the ones that eat jellyfish larva. This is due, again, to overfishing, and pollution. Since corals depend on them, they then starve. Coral bleaching refers to the loss of color of corals due to stress-induced expulsion of symbiotic algae. The corals that form the structure of the great reef ecosystems depend on a symbiotic relationship with photosynthesizing algae called zooxanthellae that live within their tissues. Zooxanthellae give coral its particular coloration. These may be expelled when the coral is stressed or killed, leaving the coral white. Some types of coral bleaching are caused by wind erosion - dirt is blown off the continents that contain certain kinds of infectious bacteria. Also, changes in ocean currents can cause a rise in water temperature, which encourages greater and unbalanced growth in some species, but not in others, leading to an ecological imbalance, bacterial growth, red tides, and toxin build up. Sometimes bleached coral can recover if it's not too far gone, by a recolonization of the coral by zooxanthellae. But if the coral is actually fully white, it is dead. Once bleaching begins, corals tend to continue to bleach even if the stressor is removed. If the coral colony survives, it often requires months for the remaining symbiont population to reach a normal density. Corals may be recolonised by the same species of zooxanthellae, or by a different species. Different types of zooxanthellae respond differently to environmental conditions and may be more resistant to coral bleaching than other species. Some corals are known to host multiple types of zooxanthellae within an individual coral. Ability to withstand stress and bleaching and ability to recover from a bleaching event varies greatly across coral species. Large massive corals, such as Porites lobata is able to withstand extreme temperature shocks, while fragile branching corals, such as Acropora are far more susceptible to dying following a bleaching event. Corals consistently exposed to low levels of stress may in fact be more resistant to bleaching. Due to the patchy nature of bleaching, local climatic conditions such as shade or a stream of cooler water can reduce the risk of bleaching.