Coral Reefs Volume 29 Number 3, 637-648, DOI: 10.1007/s00338-009-0562-0
Bleaching occurs when corals eject zooxanthellae as a result of thermal stress. This causes changes in pigmentation, and corals then appear lighter or ‘bleached.’
Corals in the Great Barrier Reef near shore waters show high levels of bleaching with high water temperatures. Studies between 1985-2007 along the shoreline of the Great Barrier Reef, were done to predict if damage could be recovered in hard coral covering that is divided into two groups: Acropordae, and the rest of hard coral species. Hard cover coral increases faster than other families such as soft coral, with the median of 11% annum, and 4% for others.
Acroporidae showed recovery from cyclone damage. During periods of time with no disturbances, recovery was observed, but the impacts from bleaching were too severe and showed decline in hard coral covering. Coral will not withstand bleaching in the long run.
The Australian region surrounding the Great Barrier Reef, should make brood stock more available, and directly protect corals from rising temperatures.
Great Barrier Reef Concerns
Skeptical Science doi:2011
The Great Barrier Reef has survived past climate changes with higher carbon dioxide rates and warmer temperatures than today. Even so, there should be concerns about ocean acidification currently effecting the Great Barrier Reef.
In the past, during glacial periods, sea levels were 100 m lower than they are today. The Great Barrier Reef was left exposed, and after the glaciers melted, the reefs were covered with soil.
The changes during the melting of glaciers, occurred over a span of 10-20,000 years. Today, temperatures change by 5-8 degrees Celsius by 100 ppm, over a time span of less than 100 years. The rate of change is significantly 100-200 times faster than in the past. The northern end is more adjusted to warm temperatures, and animals cannot cross 2500 km within 100 years, or 25 km per year, to the southern end.
Humans depend ecologically, and economically due to tourism, on the Great Barrier Reef. Unfortunately, rapid changes are occurring with very little time to adjust.
The sun was beating hard. The water was glistening. The wind was whipping by my face as the boat began to approach what I had been told was the most expansive, intricate and beautiful wonders of the world.It was December of 2010 and I was in Australia with my family on a boat that would take us to the Great Barrier Reef for an unforgettable afternoon adventure. We approached the coral reef and saw endless reefs and colorful corals that stretched over 1,600 miles. We spent the afternoon in amazement as we explored the different animals and corals that inhabited the region. It was an unforgettable experience. Upon reading chapter 4 of the book, I came across the section on the effects of ocean acidification on coral reefs. Immediately, my attention was captured as I was eager to learn more about the topic, given my personal experience with the Great Barrier Reef. As I read on, I was utterly shocked at the gravity of the effect of ocean acidification on coral reefs. The reef is the only structure in the world that has been entirely made by living organisms (Source 1). It is home a diverse array of aquatic organisms ranging from 2,000 fish species, 4,000 mollusk species and more than 250 different shrimp species (Source 1). However, the dire threat of rising CO2 levels in poses major repercussions for the reef and the many organisms that call it home. Most directly, ocean acidification affects the reef’s “unique ability to produce voluminous amounts of calcium carbonate,” which make up the structure of coral reefs (Source 2).
As a result, the organisms that build the reefs will calcify 10-50% less compared to rates in the 1950s (Source 2). This plummet in calcification has been unheard of in the past 400 years (Source 4). Because thousands of species and organisms occupy the reefs and rely on the intricacy of their composition, coral calcification is a significant indication of the “well-being” of reef ecosystems (Source 4). In a study investigated by researchers from the magazine, Science Magazine, annual calcification rates were obtained from over massive coral reefs within the Great Barrier Reef. Of the 13 reefs that were investigated, 12 of them, or 92.3%, demonstrated a negative linear trend in the rates of calcification as well as an average annually decline of about 1.44% (Source 4). These reefs provide food and shelter for countless organisms and support endless diversity within them (Source 3). Therefore, the loss of coral reef that will inevitably occur as a result of ocean acidification will negatively affect the marine organisms that make up the Great Barrier Reef. While sitting on the boat looking out at the endless reef surrounding me, I had no idea the danger it was in. I thought it nearly impossible for something so expansive and seemingly thriving to be suffering as immensely is it is. After “zooming-in” on the effects of ocean acidification on coral reefs, I have even more appreciation for the beauty and wonder of coral reefs than I had nearly eight months ago.
3- Ocean Acidification