Coral bleaching is currently one of the biggest threats to the great barrier reef, with damage recorded over hundreds of square kilometres. However, the best way to understand why, and how, is to take a scientific perspective. With the hallmarks of scientific writing, being about the causal relationship of the problem, and clearly identifying it, references to other trusted scientific articles, making predictions about the future effects, and identifying other complicating factors. This is not an article about climate change, rather about the current changing climate of the reef, and how it is being effected.
Coral: A living organism
Before we ask ourself; 'what is coral bleaching', We must ask, 'what is coral'?
If you open any textbook or dictionary it will say: Coral is a living organism that produces a calcareous substrate on which it grows. This is best described through illustration: The coral polyp below can be seen living in the stone it makes, as it grows. Emily.M.Eng(2018). The polyp is what gives the coral its bright colour, and eventually its structure. Over time this forms a rock skeleton for more polyps to grow, and in doing so forms a colony of polyps at a macroscopic level. Cells in the organism secret the cement-like structure over time, forming biostructures. Most corals leave behind a pattern of basal plates and theca. The result of the coral growing and leaving behind the calcium-rich rock over many years makes the structures we see today at the reef. Coral grows slowly, and Australias Great Barrier Reef, is the product of life over millions of years.
By understanding the life cycle of the coral it is easy to see the bigger picture. The Coral we see is the adult phase of a larger cycle of life. We start the cycle at the egg stage: where coral releases a small pink egg to the sea, others releasing sperm. This event on such a large scale turns the surface of the reef pink, as if timed to the perfect minute. As the corals know it is time and they all spawn together at the same time. Scientist in years gone by have been able to see this event unfold from space, via satellite imagery. Success comes with a cost, this large event expells trillions of eggs over the week. The remnants are eaten by fish and anything living on the reef taking the opportunity to eat an egg. If Successful, the fertile egg will become a new coral embryo. This plant like larvae with its fur like cilia will then settle on the reef.
Once the plant has settled on the reef it will begin the process of metamorphosis. The larvae will encrust into a shell. Weeks later the young polyp will develop a mouth and tentacles. As the polyp begins to grow it will divide asexually, into other polyps. The colony will grow until such a stage that a new hard base will form. Later the coral will grow into a mature colony.
Becoming what we know and see as the brightly coloured coral on the reef.
Media: By Emily.M.Eng
Media: By Cynthia Shaw
Photo: Whitsunday Escape Magazine
Photo: Curtacy of the BBC EARTH
Coral Bleaching: How
Coral Bleaches when it dies.
Simply over the past decade, the rise in sea level surface temperatures have greatly affected the polyps living in the coral structures. When they die they leave behind the white calcareous stone. Coral is very sensitive to temperature changes, and the water is some regions is simply now the wrong temperature for it to live.
It is important to know that different species of coral live within different temperature ranges. Just like plants and all life on earth, we survive in a range of conditions. Some coral prefers temperature ranges between 15 and 25 Degrees Celcius, some within 20 and 30Degrees Celcius. The truth being that each coral has a different tolerance, and we still don't know everything about every species of coral on the reef. It is almost an infinite problem. What we do know however, is the problem. It is that when these temperatures rise, the coral begins to die.
The problem then extends beyond, as after the coral's death, as it does not remain white. There is a chance other corals may bond to the old ones, or remaining polyps regrow it is not a likely outcome. Fast-growing algae stain the coral brown, and it usually takes over. I don't know enough about these effects; however, scientist are concerned that the presence of algae taking over large sections of the reef may not be a desirable outcome. Meaning that they are concerned about further negative effects.
The problem that we face now is that large proportions of the reef are now dying because the climate in the region is changing. Particularly regarding temperature increases in the tropics, mid tropics, and subtropics. Later seen more clearly in the zones of the reef.
Photo: XL Caitlin Seaview Survey
Photo: XL Caitlin Seaview Survey
Climate Change: How it is effecting the reef, and its zones
The first question that is raised is how much 1 degree of temperature will effect the reef. However, this is a huge misconception as the climate has been changing for many years in this region. The question we need to ask, is how much more the reef can take?
Below, climate central released a chart of the coral sea surface temperatures, and we can see a trend, for as long as records have been kept. Showing that the average temperature is now almost 7 degrees Fahrenheit warmer than the average. The significance is knowing that changes in temperature can kill a coral polyp, or coral colony. As a result, our coral can now no longer withstand the climatic changes in the region.
Originally ARC surveys the reef and combined its data to reveal 3 major sections: The North, Central, and Southern Regions. Later revising its data in an effort with the Australian Institute of Marine Science, the Australian Government and its Marine Park Authority to reveal a 4th section being the Far North Reef. Their findings were that the reef boundaries also contain different species of coral: capable of living in different conditions. However, the epicentre of the reef's damage took place in the northern reef section near Cooktown. With some reefs being damaged, and up to 83% of the coral died in those sections.
In the changing climate, and in the modern ages. The Great Barrier Reef is now dying, at an alarming rate. Scientist are incredibly worried that it may not adapt in time naturally, and it is clear that the reef needs our help in order to survive.
Media: Climate Central - The Australian Bureau Of Meteorology
Media: ARC Centre of Excellence - Coral Reef Studies
Media: ARC Centre of Excellence - Coral Reef Studies
The Recovery: Strategies
In a scientific breakthrough this month, a marine scientist experimenting with a new method of growing coral from a single polyp has created the concept of micro-fragmentation. The new process spaces polyps aside from another so they grow and heal on another providing us with an effective method of farming coral. With results showing us that we can regrow large corals that may otherwise take 30 years to grow, now in 9 months.
The University of Queensland also has released information to the media in the last week. They have found a way to grow coral larvae into polyps in underwater metal cages, and lace bags. However, photographs and footage of the success is yet to be released to the public. If successful on a larger scale, it would provide a way of mass farming new coral sections for the damaged sections of the reef.
Although the concept of farming coral and putting it back on reefs is not a new idea. The breakthrough allows us to consider the prospect of intervening in damaged sections of the reef. In order to give the reef a fighting chance at regrowing damaged sections.
Photo: ABC Australia
Photo: Coral Vita
Photo: The Atlantic, Dr David Vaughan
Coral Migration: Moving South
Fish for some time have been seen living much further south than where they usually reside, and now the coral is shifting too. In 2016 it was noted that the fish below, were migrating in order to cope with climate change. We know that through the lifecycle of the coral polyp, it is possible. The only difference being a greater amount of time will be needed.
The concern however, is that if a new species is introduced to a new section of the reef, or area. It may take over? However, at this stage scientist have seen corals growing hundreds of kilometres from their native waters. A species noted by 'The Conversation': can be seen here, as the tropical coral Acropora monticulosa was found in the Solitary Islands of Northern NSW. Growing alongside sea urchins, it is evidence of a coral migration that may take place.
As coral move to more favourable climates, it is more evidence again of our dynamic planet. Either caused by humans or not in the modern age, it is very apparent that as the climate changes, so does our sea. The only question remaining is if our coral sea can adapt or migrate in time, in order to survive these changing climates.
Photo: The Conversation - Article 8238