Thursday, September 29, 2016

35 Percent of Great Barrier Reef Is Dead, Scientists Confirm

35 Percent of Great Barrier Reef Is Dead, Scientists Confirm

ARC Centre of Excellence for Coral Reef Studies

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The Australian Research Council (ARC) Centre of Excellence for Coral Reef Studies released their estimated fatalities of the Great Barrier Reef on May 30 after conducting intensive aerial and underwater investigations. The researchers reveal that mass coral bleaching killed about 35 percent of corals in the northern and central portion of the largest coral reef system in the world.

“We found on average that 35 percent of the corals are now dead or dying on 84 reefs that we surveyed along the northern and central sections of the Great Barrier Reef, between Townsville and Papua New Guinea,” points out Terry Hughes, a professor and the director of the ARC Centre of Excellence for Coral Reef Studies at James Cook University (JCU). “Some reefs are in much better shape, especially from Cairns southwards, where the average mortality is estimated at only five percent.”

Coral bleaching is a result of several unusual environmental situations which includes increased ocean temperatures, that drives away zooxanthellae, a group of small photosynthetic algae. Consequently, the disappearance of the algae bleaches the corals or turns them into white.

Great Barrier Reef
Bleached mature staghorn coral. Credit: ARC Centre of Excellence for Coral Reef Studies

“This year is the third time in 18 years that the Great Barrier Reef has experienced mass bleaching due to global warming, and the current event is much more extreme than we’ve measured before,” adds the professor. “These three events have all occurred while global temperatures have risen by just one degree C above the pre-industrial period. We’re rapidly running out of time to reduce greenhouse gas emissions.”

The coral bleaching changes drastically going from north to south of the Great Barrier Reef, which will most likely worsen in time. Coral bleaching least affected the corals at the southern part of the reef. Nevertheless, this damage still hampers their recovery and growth.

However, the researchers say that the corals can still go back to normal if the water temperature decreases and the algae will return to them. The corals are expected to recover in the following months.

“Fortunately, on reefs south of Cairns, our underwater surveys are also revealing that more than 95 percent of the corals have survived,” says Mia Hoogenboom, who is also from JCU. “We expect these more mildly bleached corals to regain their normal colour over the next few months.”

  • Leslie Graham

    The next El Nino will be hotter still. And the one after that, and the one after that…,
    The reef is going to die in the next 30 years max.
    And meanwhile the government is investing in 19th century dinosaur ‘technology’ to appease their coal corporation masters while in the rest of the world the smart money is already pouring into the Global Renewables Revolution.
    Even Saudi Arabia is constructing massive solar power installations.
    Australia is committing economic suicide. It’s just utterly surreal to watch this happening in real time.

    • VooDude

      ”… coral populations that bleached during the last major warming event in 1998 have adapted and/or acclimatised to thermal stress. These data also lend support to the hypothesis that corals in regions subject to more variable temperature regimes are more resistant to thermal stress than those in less variable environments.”

      ”… a growing body of evidence indicates that the capacity for adaptation and acclimatisation in corals has been underestimated [13,21,26]. Even for highly susceptible coral species, variation in specific characteristics of the symbiotic zooxanthellae [27] and the coral host [28] lead to different bleaching responses among colonies. Selective mortality among individuals within populations suggests there is sufficient genetic variability upon which natural selection can act [29]. Several studies have documented increasing thermal tolerance and declining rates of bleaching induced mortality over successive bleaching episodes [21,30]. Similarly, thermal history and previous exposure to thermal stress have been shown to determine bleaching responses to contemporary thermal stress [13]. The most compelling evidence of an adaptive response at our study locations is that the taxa that showed the greatest contrast in response (Acropora and Pocillopora), have life history traits most likely to lead to rapid adaptation.”

      Guest, James R., et al. 2012 “Contrasting patterns of coral bleaching susceptibility in 2010 suggest an adaptive response to thermal stress.” PLoS One

    • VooDude

      ”…Rapid recovery, i.e. the restoration of live coral surface cover over decadal periods, has been observed in many areas, where the presence of coral survivors nearby, could serve as seed populations, facilitating recruitment…”

      ”… studies, carried out on the Great Barrier Reef complex, Australia, found notable recovery within 2 years … Five years after the disturbance, coral cover had increased to about 50% of its former level, but with marked differences in rates and patterns … ongoing studies reveal relatively slow recovery in severely impacted regions.”

      Glynn, P. W. 1993 “Coral reef bleaching: ecological perspectives.” Coral reefs

    • VooDude

      ”Coral reefs surrounding the islands lying close to the coast are unique to the Great Barrier Reef (GBR) in that they are frequently exposed to disturbance events including floods caused by cyclonic rainfall, strong winds and occasional periods of prolonged above-average temperatures during summer. In one such group of islands, in the southern GBR, the Keppel Island archipelago, climate-driven disturbances frequently result in major coral mortality… these island reefs have clearly survived such dramatic disturbances in the past, … following bleaching, Acropora corals in the Keppel Islands predominantly recover from regrowth of small amounts of remaining live tissue in apparently dead coral colonies. This is likely supplemented by recruitment of larvae from genetically similar, less disturbed populations at nearby reefs, …”

      van Oppen, Madeleine JH, et al. 2015 “A population genetic assessment of coral recovery on highly disturbed reefs of the Keppel Island archipelago in the southern Great Barrier Reef.” PeerJ

  • VooDude

    I believe the claim of coral death to be exaggerated.

    Published: 03/06/2016, updated 08Jun:Despite reported claims and counter claims over the last month about the ‘death’ of large swathes of the Great Barrier Reef, … Preliminary findings from the Great Barrier Reef Marine Park Authority (GBRMPA) and the Australian Institute of Marine Science (AIMS) show approximately three quarters of coral on the Reef has survived to date.”

    ”The vast majority of the impact is in the northern third of the Reef, … with the central and southern regions escaping significant mortality.”

    Gunn: ”❝… many corals in the northern sector will die, others will recover from bleaching over the coming months and we’re hopeful that in areas where bleaching has been minor the Reef will bounce back well.❞”

    Reichelt: ”❝… the overall mortality is 22 per cent — …❞”

    Reichelt: ”❝… the Australian Institute of Marine Science found coral cover increased by 19 per cent across the Marine Park between 2012 and 2015, nearly doubling in the southern sector…❞”

    ”More information on coral bleaching is available at http://www.gbrmpa[DOT]gov[DOT]au and http://www.aims[DOT]gov[DOT]au .”

    http://www.gbrmpa[DOT]gov[DOT]au/media-room/latest-news/coral-bleaching/2016/the-facts-on-great-barrier-reef-coral-mortality