Indonesian Coral Reefs Dying

[Ninong]

Global Warming Killing Indonesian Reefs Faster Than Expected

Water temps peaked at 93F this year vs. long-term average of 86F for that area:

Sea surface temperatures in the Andaman Sea—an area that includes the coasts of Myanmar, Thailand, the Andaman and Nicobar Islands, and northwestern Indonesia—have been on the rise. According to the National Oceanic and Atmospheric Administration’s Coral Hotspots website, temperatures in the region peaked in late May, when the temperature reached 34 degrees Celsius. This represents a dramatic 4-degree rise over the long-term averages for the area.

[FoMoCo Master Tech]

That's terrible but there may be hope still. I was watching television and came across a show called "Oceans Blue". This episode was dedicated to the reefs of the Red Sea. Toward the end of the show, they talked about the affects of rising water temperature and coral bleaching. I don't know much about marine life as I am very much a novice but what I gathered so far is that photosynthesis creates carbohydrates and fats as a by-product which are consumed by the coral as food. When water temperatures are too high, the photosynthetic algae either dies or "leaves" the coral thus, bleaching it. The show then goes on to explain that although the Red Sea water temperatures reach as high as 93 degrees F, the reefs are flourishing. The theory behind it is that there is another type of algae ( named " Symbiont D") has an unusual heat resistance. It is suspected that this algae may be the unsung hero to solve the global crisis and possibly reverse the declining reefs througout the world.
Since I'm such a newb and am clueless, I apologize if the above information is "common knowledge" but I find marine ecosystems fascinating and the more I learn, the more excited I get to learn more. I swear, im like a kid in a candy store . My wife thinks I'm crazy because I like to window shop at my lfs but what can I say, I'm hooked. My setup is still too young for coral but I hope to be able to maintain a stable enough environment to create my own marine "rain Forrest".

[Ninong]

Yes, that pretty much sums it up. The Red Sea and the Persian Gulf are influenced by their surrounding desert and lack of rainfall. Salinity and water temperatures are much higher there than in the area of other corals reefs. Corals and fish that live there have adapted to those conditions over thousands of years.

Zooxanthellae (Symbiodinium spp.) are divided into at least eight clades (A, B, C, D, E, F, G and H) based on their molecular biology. Most corals there have clade D, some have clade C and some have both D and C. That's just of the corals they have tested so far.

The problem now is that areas like Indonesia and the Philippines and the Great Barrier Reef are being hit with water temperatures above their usual seasonal highs for extended periods of time. That will cause bleaching. Once corals have adapted to a region, they cannot tolerate water temperatures more than about 2C above their average seasonal highs for periods exceeding three weeks without some bleaching.

Corals in the area of Indonesia that they're talking about in the article I linked are used to average seasonal highs of 86F (30C), but they're now experiencing temps of 93F (34C). They can't take water temps that high for any extended period of time. Corals in the Red Sea or the Persian Gulf, on the other hand, do experience seasonal peaks of 91-93F, so they're better equipped to deal with that.

Salinity in the area of most tropical reefs is approximately 35 ppt (1.0264 SG). Usually you will see it written as 35 PSU (practical salinity units) in scientific literature. Salinity in the Mediterranean Sea is approximately 37 ppt. In the the Red Sea and the Persian Gulf it can get as high as 41 ppt but it's usually around 38-39 ppt most of the year in most areas of the Red Sea. That's a lot higher than say Indonesia or the Great Barrier Reef.

Some parts of the Great Barrier Reef do experience water temps of 90-91F on a regular basis under certain conditions but the corals that thrive there have adapted to those highs. An interesting question is how quickly can coral species adapt to changing water temps if push comes to shove. That question is being studied now in terrestrial animals that are being forced to either adapt or migrate from northern areas that are experiencing sustained higher temperatures due to global climate change.

P.S. -- Another long-range problem for coral reefs is rising seawater acidity (falling pH). Back in the 19th century, it was 8.3. Today it's 8.2 and falling due to the increased CO2 in the atomosphere. If we don't do something to halt rising CO2, the pH will drop to 7.9 by the end of this century. As pH falls, the growth rate of corals slows.

Don't forget, coral skeletons are made of aragonite. Aragonite begins to dissolve at pH of 7.7 and below. If corals can survive rising water temperatures, they will still have to figure out a way to survive falling pH. What they did in the past (many millions of years ago) was to develop a calcite covering that encased their inner aragonite skeleton. Calcite begins to dissolve at pH of 7.4 and below. Aragonite and calcite are just different crystalline structures of the same thing (CaCO3).

However, any exposed aragonite would still dissolve away over time if the pH of the water dropped down to say 7.6. I think that means that the foundation of the coral reefs would slowing disappear. That's not cool.

[FoMoCo Master Tech]

Thanks for the interesting insight. How long it will take for adaptaion is definately the million dollar question. I wonder how massive the domino effect will be considering the rate of reef decline and just how much of the ocean's life depends on those reefs. Kinda scary to imagine.