Warming Corals [Research]

1.Why should you care?

Warm waters, tropical islands, a gentle coastal breeze… These few words paint an image of the typical summer vacation most people dream of enjoying. In fact, most people won’t venture into ocean waters unless they seem warm enough to enjoy. However, as many environmental changes occur around our earth (both natural and human-accelerated), our oceans are feeling the effects of warming waters.

Among other areas, the waters around tropical areas such as the Great Barrier Reef off the coast of Australia are experiencing warming anomalies. These unexpected changes in ocean temperature can negatively and sometimes positively impact the ecosystem processes that occur in the local reefs. This is important because we as humans depend on coral reefs for numerous reasons.

Coral reefs around the world provide habitat for millions of different marine species that together allow the sea to function properly. They provide us with food food, water, and simple pleasures from the ocean. They also provide jobs to millions of people in the form of marine management systems, fish nursery employment opportunities, marine food exporters, scuba diving explorers, vacation tours, researchers, and many others. Reefs also create a natural barrier to the land they surround preventing stormy waves from raging onto land at full speed. And in addition to others, the marine species that live within the reefs provide food to locals in the area – and possibly to your own dinner table.

But did you know that coral reefs are ALIVE? They feed, grow in colonies, and reproduce just as other species do in the area, yet at much slower rates. They are a keystone species within their ecosystems providing other species the ability to live simultaneously from the benefits they provide (and vice versa). Reefs are capable of being damaged, becoming infected with diseases, and face endangerment in many areas due to changing ocean temperatures altering ecosystem processes.

Without coral reefs, the oceans we depend on for food and health will not be able to function as efficiently as we require them to. And as they face a changing climate among other issues, reefs are in need of your protection and consideration. Even if you think you are too far away from reefs like the Great Barrier to make a difference, your actions at home have an impact on the immediate environment. Our actions can and will eventually impact the reefs around the world that our so important to our lives and to the well-being of many other animals. For example, the addition of pollutants to the ocean (whether directly or by runoff), the overfishing of marine life, and our growing need to better manage areas around coral reefs all can have an potential impact on reef health.

Check out this short video (by clicking here) to see some awesome images of coral reefs – and some saddening ones as well to learn more about what is going on. Then read on to explore a specific example of how colonies of coral reef off the coast of Australia are impacted by rising sea temperatures.

2. Why was this study carried out?

The researchers of this study wanted to identify if ocean water warming anomalies (or random increases in ocean temperature due to climate change) can increase the disease potential for coral reefs. This is important because more specific research aimed at understanding how to prevent coral reef loss across the globe is needed.

3. How was the study carried out?

A total of 48 reefs were surveyed over 6 years and across over 900 miles of coral in the Great Barrier Reef. Carrying out the study for 6 years allowed more accurate measuring of ocean temperature variations through a longer period of time to better identify if/how changing ocean temperatures can increase rates of disease in reefs. Scientists surveyed the number of reefs during this time and across the area infected with a disease called White Syndrome. They also looked at the total coverage of coral in the areas to see if their was a relationship between larger reef colonies and White Syndrome disease.

4.What were the results of the study?

When compared to smaller reefs in warming waters, colonies of coral reef with greater amounts of overall cover (meaning they encompassed a larger area) had higher levels of diagnosed White Syndrome disease. From this, researchers suggest that warming waters can potentially decrease the ability of corals to resist disease, especially when they span over larger areas. Additionally, when the waters surrounding coral reefs fluctuate between cooler and warmer temperatures, additional health hazards can occur. Researchers found that warming waters can increase the opportunity for the spread of various diseases between multiple colonies.

Researchers also suggest that high areas of coral reef cover are able to spread White Syndrome more quickly due to the decrease in distance between different colonies. In contrast, reefs with lower levels of cover were less likely to become diseases ridden even when located in warming waters. However, in addition to smaller coverage, many of the reefs were already experiencing coral bleaching – preventing them from also being infected by White Syndrome.

Additionally, reefs lacking the proper abundance of local marine life experienced decreased health levels – as their usual ecosystem processes became impaired. This also prevented the reefs from being able to remain healthy overall. However, researchers suggest that marine life can also act as a vector for the spread of diseases in coral colonies. Because of this, it is important that consideration is given not to just the corals – but to the fish and surrounding water quality of the area as well. Even healthy corals that are surrounded by disease ridden reefs suffer from various ripple effects.

Furthermore, rising sea temperatures can reduce the abundance of keystone species and others which create the proper habitat for reefs to grow in. Without the proper habitat and the combined effects of warming waters, reefs are suffering at greater rates than naturally expected. For this reason, studying how reefs are directly impacted by warming waters is crucial, however; it is also important to consider what changing temperatures due to the local fish species as well.

Overall, there are many abiotic and biotic stressors that can impact coral reef immunity and susceptibility to getting disease such as White Syndrome. All are in need of consideration in order to ensure that the remaining reefs are sustained and others given the chance to regrow over long periods of time.

5. Want to know more details?

What do you think? Any questions? Please send them my way in the comment box below and I will do my best to find out the answers for you or to just respond back.

Also, check out the original article, Thermal Stress and Coral Cover as Drivers of Coral Disease Outbreaks, if you would like to view a more detailed version of the information summarized in sections 2-4 above.

Authors: John Bruno, Elizabeth Selig, Kenneth Casey, Cathie Page, Bette Willis, C. Harvell, Hugh Sweatman, Amy Melendy.

Published: June 2007 by PLoS Biology


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