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disappearance of coral reefs - a question

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disappearance of coral reefs - a question

Old 1st Dec 2016, 15:38
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bbrio asks

What I don't understand is why they don't slowly spread to (cooler) waters where they can thrive. This is not meant to be a discussion of the evidence of rising sea temperatures, I want to know what will happen to the coral.
The reef building coral that depend on energy supplied by their photosynthesizing symbionts thrive in the world's warmest oceans but can be limited by sunlight. Sediments that block the sun can be fatal. Due to the declining angle of the sun's rays, as coral move poleward they do not receive enough sunlight. Furthermore colder winters cause bleaching. There was massive bleaching of Florida coral in 2010, the worst observed there, due to the cold winter. Thus most symbiotic coral are limited to the tropics

A scientific paper on Florida's winter bleaching is found at PLOS ONE: Severe 2010 Cold-Water Event Caused Unprecedented Mortality to Corals of the Florida Reef Tract and Reversed Previous Survivorship Patterns

(There are deep water reef-building corals that do live in cooler waters but they do not depend on photosynthesizing symbionts and therefore do not bleach. Those coral depend in filter feeding)

Tropical coral will increase their number of symbionts during the relatively low light of winter but then decrease that number during the summer. Thus mild bleaching is observed seasonally. Nutrients and carbon are often limiting. Thus under high light conditions during the summer the photosynthetic process can be overwhelmed. Instead of producing beneficial organic molecules, more reactive oxygen radicals are produced that are harmful. (Humans ingest vitamins and antioxidants for protection from those radicals) So tropical coral eject their symbionts temporarily to minimize such deleterious effects.

As irradiance declines coral re-acquire symbionts. However during this re-acquisition coral may acquire different and genetically distinct symbionts with various advantageous traits. If bleaching was due to a climate shift as well as seasonal stress, some of those newly acquired symbionts allow coral to quickly adapt to those changing conditions.

Experiments have induced bleaching at colder temperatures by simply increasing irradiance. In nature many of the worst cases of bleaching happen where clear skies increase irradiance, which also increases temperatures
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Old 1st Dec 2016, 15:49
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Yamagata ken says, "Welcome Jim Steele and thanks for responding. Apologies, I didn't intend to drag you into (yet another) internet spat."
No worries ken. I am glad to provide my scientific insights. Good science is about sincere debate that vets all hypotheses, so the world of science is full of spats.

Only the personal attacks denigrate the scientific process, and unfortunately there are internet snipers who try to do so.

I look forward to promoting a more scientific discussion here if people are interested.
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Old 1st Dec 2016, 20:16
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In a June 2016 article Great Barrier Reef: Survey off Townsville finds increase in coral despite recent bleaching they report on surveys of reefs near Townsville in the Great Barrier Reef’s central sector. Here NOAA estimated 33% of the reefs had suffered severe bleaching and only 10% of the reefs experienced no bleaching in 2015. This sector’s reefs had also suffered greatly from cyclone Yasi in 2011, yet “[s]cientists also found coral cover on seven of the reefs were at its highest levels since they were first surveyed 30 years ago.”

One must wonder, if lost coral is mainly due to climate then why would some reefs exhibit "highest levels" of growth over the past 30 years. Part of the answer to that questions is bleaching only comprises a small portion of reef mortality.

As illustrated by the pie graph from Osborne 2011, in the Great Barrier Reef the explosion of the coral-eating Crown of Thorns starfish (A. planci) and tropical storms contributed to the greatest loss of coral colonies, 70.5%. Bleaching is a very minor contributor to coral mortality, just 5.6%, and that bleaching can be induced by warm or cold temperatures, heavy rains and floods or high irradiance from anomalously clear skies


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Old 2nd Dec 2016, 07:37
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Jim

That would be extremely interesting. It is not just climate change but man made damage through dragging while fishing that needs to be stopped as well as the millions of Sharks killed for their Fins which will change the whole balance of not just Corals in the Sea
I have dived with numerous Varieties of Sharks and they are amazing creatures.

I have only ever felt threatened once which was an Oceanic White tip on a drift dive in the Red Sea. There was an attack on a German swimmer by a white tip who are oceanic being forced into shallower waters as their staple fish diet has been overfished.
I will never forget the Majestic outline of Hammerheads in the Maldives in deep water when we missed a reef.
Not the creatures so feared by the unknowing and depicted in films like jaws

There are millions of Sharks killed every year as well as the Mantas and I find it amazing that world Government allow such fishing abuse to continue

It is the whole balance of the marine world which is interdependent not just the corals
It is 100 million sharks killed a year for a tasteless fin
That is a disgusting number and has to be stopped

Last edited by Pace; 2nd Dec 2016 at 08:47.
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Old 2nd Dec 2016, 08:51
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There are millions of Sharks killed every year as well as the Mantas and I find it amazing that world Government allow such fishing abuse to continue

Well, you have to consider the sources. how many world government leaders (Asia) like bellying up to shark fin soup? How many of them like to indulge in the benefits of powdered Rhinoceros Horn or bear bile potions?


Or if you mean by "world government", the UN? HA!
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Old 2nd Dec 2016, 09:58
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Yes it's predominantly Asia part has to be government pressure, pressure from conservation organisation and education of the reality to the people so the demand itself goes
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Old 2nd Dec 2016, 10:24
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A few years ago I had to deal with several marine scientists.

My considered opinion is that they fell somewhere between astrologers and the flat earth society. Maybe closer to to astrologers, I always had the impression that the flat earther I knew was in it for the entertainment value.
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Old 2nd Dec 2016, 13:01
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Many thanks to all the posters on this topic. Much more to this business than meets the eye, but at least I know a lot more about the problem.
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Old 2nd Dec 2016, 15:47
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If undisturbed by destructive human practices such as landscape changes that increase sediments and destructive practices like dynamite fishing, coral reefs are thriving despite climate change. Research published in the journal Proceedings of the Royal Society B show that coral reefs surrounding remote islands were dramatically healthier than those in populated areas that were subject to a variety of human impacts. The lead author of that research was encouraged to state, “There are still coral reefs on this planet that are incredibly healthy and probably look the way they did 1,000 years ago.”

Concerned with the El Nino induced bleaching event, Dr. Smith more recently reported protected reefs on “Palmyra did bleach in 2015, revealing haunting white landscapes”. But when an expedition returned to assess mortality and recovery in May 2016 she reported, “We sent team of 8 scientists to Palmyra for 6 days to assess the recovery of Palmyra’s coral reefs to the current warm water impacts of El Nino. On the first dive, it was hard to remember where the bleaching had been. The corals were full of color.” Although she warns this doesn’t necessarily mean Palmyra’s reefs are immune from future warming, “we are excited to learn from Palmyra’s reef communities to understand how the rates and patterns of regrowth and recovery influence resilience.”

Such resilience is exactly what the adaptive bleaching hypothesis would predict.
Thanks Ken for posting

The Coral Bleaching Debate: Is Bleaching the Legacy of a Marvelous Adaptation Mechanism or A Prelude
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Old 3rd Dec 2016, 06:36
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In the 70s wasn't the Great Barrier Reef in danger because it was being consumed by Crown of Thorns starfish?
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Old 3rd Dec 2016, 07:24
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Yes Cd Taylor, and then by the runoff from cane farming. As you realise, this is just the latest iteration of the cycle of coral on the Barrier Reef
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Old 3rd Dec 2016, 15:00
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Some people suggest a lower pH is a threat to coral but recent research shows it is beneficial.

In order to sustain photosynthesis, corals actively pump hydrogen ions (H+) into the vesicles encapsulating their algal symbionts. This lowers its internal pH to truly acidic levels between pH 4 and 5 (Barott 2015). This increases H+ concentrations up to 10,000 times greater than any theoretical contributions to surface waters by atmospheric CO2. If coral do not acidify their symbionts’ surroundings, the limiting supply of CO2 would dramatically decrease the rate of photosynthesis.
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Old 5th Dec 2016, 00:06
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Due to long-term sequestration of CO2 that exceeds respiration, we would expect surface ocean pH to remain above 8.1 for the short term. However due to the release of CO2 during calcification, reef pH drops far below 8.1. Calcification infuses the surface waters with an excess of CO2 largely driving the nighttime pH down as low as 7.7. Furthermore at a pH below 8.1, CO2 concentrations in the ocean’s surface rise higher than the atmosphere’s, and this results in nighttime out-gassing of CO2. Instead of CO2 invading the ocean and affecting coral, overall measurements show coral reefs are net sources of CO2 from the ocean to the atmosphere. Similar dynamics from calcifying coccolithophores likewise promote CO2 fluxes from the open ocean, and inhibits uptake from the atmosphere.
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Old 5th Dec 2016, 22:21
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As illustrated below in Figure 1 from Lamy 2016, an outbreak of COTS removed 80% of the live coral cover between 1979 and 1982, reducing total coral cover to 10% of the reef. However by 1991 the coral had fully recovered. As designated by the small gray arrows at the top, three bleaching events occurred during that recovery period. Later destruction from a 1991 cyclone again reduced coral cover but again coral recovered reaching its greatest coverage of 50% by the year 2000. And again during that recovery there were 3 more bleaching events. Since 2006 the coral suffered their greatest loss due to another outbreak of COTS, quickly followed by another cyclone. High mortality promoted high seaweed cover (dotted green line) that has inhibited coral recovery. Over that time, coral bleaching was associated with periods of recovery, suggesting little if any detrimental effects. One could reasonably argue those bleaching events were beneficial.

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Old 6th Dec 2016, 00:30
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Extreme views by researchers like Hoegh-Guldberg (2014) have speculated 95% of the coral will be lost by 2050, and he argues our current high levels of CO2 are creating conditions coral have not experienced for millions of years. Yet in terms of pH (and temperature) such “scientific” claims are pure nonsense. First a modeled average surface pH tells us very little about the pH that directly affects marine organisms locally. Due to the counteracting effects of photosynthesis, respiration and calcification, coral reefs can experience a pH hovering around 8.5 or higher during the day followed by a low pH of 7.8 or lower at night. Kline 2015 acknowledged, “As with many other reefs, the nighttime pH minima on the reef flat were far lower than pH values predicted for the open ocean by 2100.” Elsewhere researchers concluded that in addition to atmospheric pH, the complex interactions controlling pH especially in coastal zones, make detection of any trends towards acidification “not trivial and the attribution of these changes to anthropogenic CO2 emissions is even more problematic.” (Duarte 2013)
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Old 7th Dec 2016, 19:49
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Here's the graph from Kline 2015 showing that every day, due to reef respiration and calcification, coral experience much lower pH than the 8.1 pH that climate models suggest is dude to atmospheric CO2. Clearly the biosphere exerts greater control on ocean pH.


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Old 7th Dec 2016, 20:06
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Originally Posted by Hempy View Post
Suggest you do a little more research on that SARF, pH is exponential. I know that sites like the Smithsonian, Scientific American, NOAA etc are nowhere near as reliable a source as, say, WUWT, but anyway..

Ocean Acidification | Smithsonian Ocean Portal

https://www.scientificamerican.com/a...-in-the-ocean/

What is Ocean Acidification?
Ok a ph,rise,of 0.1 can be described as a 25 per cent increase in acidity as the OP did.
The headline needs some work though to give it a sense of scale ..
You could say the sea is 25 per cent less caustic.
Or that if there is a further 1500 % increase in acidity then the sea would have the same ph as river water ..
Also what in the +\- margin for error. Especially as we are measuring the whole oceans ph from the start of the industrial revolution.
what was the sample amount Where were the samples taken ..
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Old 8th Dec 2016, 03:20
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via Hempy #35:
Sorry Binghi, but citing an Andrew Bolt article written 8 months ago on the condition of the GBR is akin to citing 911Truth on the Twin Towers or the KKK on race relations.

Take a closer look at the article that Bolt cites, 05 April: Condition of Great Barrier Reef corals before the mass bleaching event in 2016

From the same source, but more recently... Bleaching Events - AIMS

I know it doesn't suit your agenda, but your 'fact based evidence' seems a little light on actual 'facts'....or 'evidence'.
Bit hysterical there Hempy.. I had a look-see at yer links and i see nothing to disprove the Bolt article.

Hempy, as yer seem to be the font of hysteria based coral knowledge, perhaps yer can tell us all about the massive bleaching event of 1974/75. Soon after the big Queensland floods of that time.........






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Old 12th Dec 2016, 07:05
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How goes Hempys research on the 1974/75 coral bleaching event. I've not found any reference and yet according to the links Hempy provided floods cause coral bleaching.
Perhaps the storys of 'science' not actually studying coral bleaching until the 1980's is true.. Now that would put todays bleaching hysteria false claims in context..




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Old 12th Dec 2016, 20:43
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@jimsteele
Interesting to see from your graph the compounding effect of a COTS event and a cyclone shortly thereafter.
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