Coral Bleaching: What (or Who) Dunnit?

[sunsettommy]

From TCSDAILY,

Coral Bleaching: What (or Who) Dunnit?

By Dr. Gary Sharp : BIO (http://www.tcsdaily.com/Authors.aspx?id=266)| 26 Apr 2006

Excerpt,

Thanks to a Senate hearing on global warming this week, Americans can expect a plateful of charges about dangers to our oceans and, in particular, coral reefs. They should take it all with a pinch of sea salt.


It's not that the objects of alarms -- particularly the condition of reefs in the Indian Ocean region, raised by such nongovernmental organizations as the World Wildlife Fund (WWF) and the Pew Charitable Trusts -- aren't of concern. Coral reefs are appropriately compared to the world's rain forests as habitats for wide varieties of life. They deserve protection.


But against what? Before we blame global warming, yet again, for a change in a species behavior or environment, we need to look closely at what is most likely to affect the reefs, and what is not.


The dying off of coral reefs is known as coral bleaching. This bleaching occurs when corals expel the symbiotic algae -- or Zooxanthellae -- that live in their tissues. This is usually in response to environmental stress, in particular high sea-temperatures, but also high solar radiation, fluctuating salinities, extremely low tides and often a combination of these factors. Then, of course, there are the several instances of pollution associated with several island locations -- mostly those with poor local sewage treatment and/or luxury liners dumping their sewage within close vicinity.

(More)

http://www.tcsdaily.com/article.aspx?id=042606B

The best stuff is in the link.

The regions where the reefs lives has a large natural temperature variation.They live in both warmer and cooler waters.

[Aussie]

I don't know about him saying that a change in sea temperatures won't affect coral reefs that much. Australia is the proud protector of the Great Barrier Reef, the most biologically diverse and biggest of its type. It suffered terrible bleaching in 2002 and 1998 because the water temperature was 1-2 degrees more that usual.

The summer of 2001-2002 was a mass bleaching event that was more severe than the 1998 event. In response to this event, the Great Barrier Reef Marine Park Authority implemented the world’s most comprehensive survey of coral bleaching in collaboration with AIMS, CRC Reef and NOAA. Aerial surveys observed bleaching in almost 60% of the 641 reefs observed. This made the event the worst on record.

...Underwater surveys found that few reefs had completely escaped the effects of coral bleaching. However, the majority of reefs appear likely to survive the bleaching event with only minimal coral death. Extensive mortality was recorded on only a few of the inshore reefs surveyed, where up to 90% of corals were dead. Inshore reefs were more severely affected by bleaching, as was the case in 1998. However, in 2002 many offshore reefs were also affected.

leaching and mortality were most evident in shallow sites. This research concluded that high sea temperatures combined with periods of calm seas, high light, and in some areas, reduced salinity as a result of flooding, caused the major bleaching events. Records of water temperature show that sea temperatures were 1 – 2°C higher than long-term average values in the central and southern Great Barrier Reef during the bleaching period.

From here. (http://www.reeffutures.org/topics/bleach/event.cfm)

[sunsettommy]

Records of water temperature show that sea temperatures were 1 – 2°C higher than long-term average values in the central and southern Great Barrier Reef during the bleaching period.

So does that mean this is a normal event when the surface temperature deviates as it would be expected from time to time?

How would they know it is THE cause of the problem when Coral reefs live in regions in much cooler water and warmer waters and do fine.

The article I posted seems to think it is POLLUTION that is the primary cause.


The dying off of coral reefs is known as coral bleaching. This bleaching occurs when corals expel the symbiotic algae -- or Zooxanthellae -- that live in their tissues. This is usually in response to environmental stress, in particular high sea-temperatures, but also high solar radiation, fluctuating salinities, extremely low tides and often a combination of these factors. Then, of course, there are the several instances of pollution associated with several island locations -- mostly those with poor local sewage treatment and/or luxury liners dumping their sewage within close vicinity.



He also says this:


The temperature increase, though, would fall within the range of temperatures along the reef today -- from 29-30 degrees Celsius (84-86 degrees Fahrenheit) in the north to around 23 degrees C (73 degrees F) in the south. And yet reefs exist nearly everywhere along this 6 to 7 degree C (11-13 F) gradient.


We have seen that sea surface temperature change regularly a degree or two.The reefs handle it fine.

I think you miss the part about strong El-Nino events of 1998(strongest on record) and 2002(a long lasting one).They increase the water surface temps a few degrees for a time.They can contribute to the stress on the coral reefs.

Here is a link to the current Sea surface temps:

http://www.ssec.wisc.edu/data/sst/latest_sst.gif

[DeclinetoState]

Face, it's all Bush's fault. If a sea anemone stings one too many (or one two few) of its prey (or whatever is unfortunate enough to get too close), it's Bush's fault (or if not Bush, at least conservatives are to blame). If a whale bumps its head on the bottom of the sea, it's Bush's fault. If a fish's fin gets nicked when it barely escapes from a predator, it's all Bush's fault.

[Aussie]

We have seen that sea surface temperature change regularly a degree or two.The reefs handle it fine.That's what I contest. The Great Barrier Reef and lots of other reefs around the world didn't seem to think a two degree change was fine.

I think you miss the part about strong El-Nino events of 1998(strongest on record) and 2002(a long lasting one).They increase the water surface temps a few degrees for a time.They can contribute to the stress on the coral reefs.I'm fine about the reasons for the temperature change. I just don't think the writer's right in saying that a one or two degree change won't affect reefs that much.