Breeding baby corals for warmer seas

March 26, 2019 by Dr Nerissa Hannink, University of Melbourne

A unique collection of baby corals has just begun to grow under the waves of the Coral Sea.

Hoping to give mother nature a helping hand, researchers have bred the corals to make them better able to cope with our changing climate – rising sea temperatures and increased acidity.

They are now growing in experimental field conditions on the Great Barrier Reef, to see if they can also thrive in the wild.

Professor Madeleine van Oppen, an Australian Research Council Laureate Fellow at the University of Melbourne and the Australian Institute of Marine Science (AIMS), is leading the project.

"Most corals in the wild are living at the very top of their survival limit in terms of temperature," Professor van Oppen says.

"The Great Barrier Reef lost half its coral cover during the back-to-back heat-induced mass bleaching events of 2016 and 2017."

She notes that the Great Barrier Reef has warmed by around 0.6 °C since the 1950s, contributing to more extreme and frequent marine heatwaves.

"Without a curb on greenhouse gas emissions, tropical sea temperatures are predicted to rise by 2-3°C by the end of the century compared to pre-industrial times. So it is vital we help corals adapt," Professor van Oppen says.

During summer heatwaves, corals become stressed and lose the microalgae that normally reside inside them in a mutually beneficial, or symbiotic, relationship. Corals receive most of their nutrition from the algae, so without them they starve and often die, turning white – coral bleaching.

Climate change also means that oceans absorb more carbon dioxide from the atmosphere, which makes seawater more acidic. When combined with rising temperatures, increased acidity can make coral more sensitive to bleaching – making it more difficult for them to form their calcium skeletons.

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Coral decline in Great Barrier Reef 'unprecedented'

Reef monitoring program shows northern section has lost half of its coral cover

Ben Smee

Tue 5 Jun 2018 07.08 BSTLast modified on Tue 5 Jun 2018 07.09 BST

A steep decline in coral cover right across the Great Barrier Reef is a phenomenon that “has not been observed in the historical record”, a new report by the Australian Institute of Marine Science says.

The institute, Australia’s government-backed marine research agency, periodically releases results of a long-term reef monitoring program. Each reef along the Queensland coast is visited by researchers every two years to assess its condition and coral cover.

The latest results, released on Tuesday, detail how major bleaching events in 2016 and 2017 have impacted on different sections of the reef. AIMS said it had no previous record of bleaching events occurring in successive years.

“Over the 30-plus years of monitoring by AIMS, Great Barrier Reef reefs have shown their ability to recover after disturbances, but such ‘resilience’ clearly has limits,” the report says.

 “The predicted consequences of climate change include more powerful storms and more frequent and more intense bleaching events.

“More intense disturbances mean greater damage to reefs, so recovery must take longer if the growth rate remains the same. At the same time, the intervals between acute disturbance events are decreasing and chronic stresses such as high turbidity and high ocean temperatures can slow rates of recovery.”

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Deteriorating Great Barrier Reef hushed: Young fish no longer hear their way home

April 30, 2018, University of Exeter

Degraded coral reefs are far quieter than five years ago, and no longer sound like a suitable habitat to young fish searching for a place to live and breed, according to research published today in Proceedings of the National Academy of Sciences.

Baby fish looking for a home can use noisy coral reef sounds including snapping shrimp clicks, damselfish chirps, and clownfish chattering to locate and select suitable habitat. But that "coral reef orchestra" has been quietened following recent cyclone and coral-bleaching damage on the Great Barrier Reef, raising fears that young fish may no longer hear their way home.

An international team of scientists, led by the University of Exeter, carried out field experiments on the Northern Great Barrier Reef and found that reefs sound much quieter and less acoustically diverse than they did before three years of cyclones and coral bleaching.

The soundscapes of these recently-degraded reefs are less attractive to juvenile fishes attracting 40% fewer fish compared to the sound of previous healthy reefs.

Lead author Tim Gordon, a marine biologist at the University of Exeter, said: "It's heart-breaking to hear. The usual pops, chirps, snaps and chatters of countless fish and invertebrates have disappeared. The symphony of the sea is being silenced."

This loss of attractiveness of reef sounds to fish in the sea could have devastating consequences for reefs.

Fish communities are instrumental to maintaining healthy reefs by removing algae, facilitating coral growth, contributing to nutrient cycles and keeping food webs in balance. Damaged reefs with healthy fish populations recover faster than reefs that have lost their fish.

Harry Harding, co-author from the University of Bristol, explains: "If fish aren't hearing their way home anymore, that could be bad news for the recovery prospects of reefs. Fish play critical roles on coral reefs, grazing away harmful algae and allowing coral to grow. A reef without fish is a reef that's in trouble."

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Global warming is transforming the Great Barrier Reef

April 18, 2018, ARC Centre of Excellence in Coral Reef Studies

A new study published online today in Nature shows that corals on the northern Great Barrier Reef experienced a catastrophic die-off following the extended marine heatwave of 2016.

"When corals bleach from a heatwave, they can either survive and regain their colour slowly as the temperature drops, or they can die. Averaged across the whole Great Barrier Reef, we lost 30 per cent of the corals in the nine month period between March and November 2016," said Prof Terry Hughes, Director of the ARC Centre of Excellence for Coral Reef Studies (Coral CoE).

The scientists mapped the geographical pattern of heat exposure from satellites, and measured coral survival along the 2,300-km length of the Great Barrier Reef following the extreme marine heatwave of 2016.

The amount of coral death they measured was closely linked to the amount of bleaching and level of heat exposure, with the northern third of the Great Barrier Reef being the most severely affected. The study found that 29 per cent of the 3,863 reefs comprising the world's largest reef system lost two-thirds or more of their corals, transforming the ability of these reefs to sustain full ecological functioning.

"The coral die-off has caused radical changes in the mix of coral species on hundreds of individual reefs, where mature and diverse reef communities are being transformed into more degraded systems, with just a few tough species remaining," said co-author Prof Andrew Baird of Coral CoE at James Cook University.

"As part of a global heat and coral bleaching event spanning 2014-2017, the Great Barrier Reef experienced severe heat stress and bleaching again in 2017, this time affecting the central region of the Great Barrier Reef," said co-author Dr Mark Eakin of the U.S. National Oceanic and Atmospheric Administration.

"We're now at a point where we've lost close to half of the corals in shallow-water habitats across the northern two-thirds of the Great Barrier Reef due to back-to-back bleaching over two consecutive years," said Prof Sean Connolly of Coral CoE at James Cook University.

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How to Stop Sex Changes in Turtles on the Great Barrier Reef-Climate change led to more female eggs, so scientists are trying to ensure males are made in the shade - via Herp Digest

by Anita Rita Patricia, The Conversation US, 1/17/18

                       

Credit: Alaina McDavid Flickr (CC BY-SA 2.0)

The following essay is reprinted with permission from The Conversation, an online publication covering the latest research.

In the northern part of Australia’s Great Barrier Reef, the future for green sea turtles appears to be turning female.

A recent study has revealed that climate change is rapidly leading to the feminisation of green turtles in one of the world’s largest populations. Only about 1% of these juvenile turtles are hatching male.

Among sea turtles, incubation temperatures above 29ºC produce more female offspring. When incubation temperatures approach 33ºC, 100% of the offspring are female. Cooler temperatures yield more males, up to 100% near a lower thermal limit of 23ºC. And if eggs incubate at temperatures outside the range of 23-33ºC the risk of embryo malformation and mortality becomes very high.

As current climate change models foresee increases in average global temperature of 2 to 3ºC by 2100, the future for these turtles is in danger. Worryingly, warmer temperatures will also lead to ocean expansion and sea-level rise, increasing the risk of flooding of nesting habitats.

HOW SCIENTISTS ARE TACKLING THE PROBLEM

Green sea turtles’ sensitivity to incubation temperatures is such that even a few degrees can dramatically change the sex ratio of hatchlings.

Sea turtles are particularly vulnerable because they have temperature-dependent sex determination, or TSD, meaning that the sex of the offspring depends on the incubation temperature of the eggs. This is the same mechanism that determines the sex of several other reptile species, such as the crocodilians, many lizards and freshwater turtles.

Scientists and conservationists are well aware of how future temperatures may threaten these species. For the past two decades they have been investigating the incubation conditions and resulting sex ratios at several sea turtle nesting beaches worldwide.

This is mostly done using temperature recording devices (roughly the size of an egg). These are placed inside nest chambers among the clutch of eggs, or buried in the sand at the same depth as the eggs. When a clutch hatches (after 50 to 60 days) the device is recovered and the temperatures recorded are analysed.

Research has revealed that most nesting beaches studied to date have sand temperatures that favour female hatchling production. But this female bias is not immediately a bad thing, because male sea turtles can mate with several females (polygyny). So having more females actually enhances the reproductive potential of a population (i.e. more females equals more eggs).

But given that climate change will likely soon increase this female bias, important questions arise. How much of a female bias is OK? Will there be enough males? What is the minimum proportion of males to keep a sustainable population?

These questions are being investigated. But, in the meantime, alarming reports of populations with more than 99% of hatchlings being female stress the urgency of science-based management strategies. These strategies must be designed to promote (or maintain) cooler incubation temperatures at key nesting beaches to prevent population decline or even extinction.

THE CHALLENGE OF REVERSING FEMINISATION

There are two general approaches to the problem:

            1          mitigate impacts at the most endangered nesting beaches

            2          identify and protect sites that naturally produce higher proportions of males.

Several studies emphasise that the natural shading native vegetation provides is essential to maintain cooler incubation temperatures. Thus, a key conservation action is to protect beach vegetation, or reforest nesting beaches.

Coastal vegetation also protects the nesting beach against wave erosion during storms, which will worsen under climate change. This strategy further requires coastal development to allow for buffer zones. Construction setback regulations should be enforced or implemented.

When natural shading is not an option, clutches of eggs can be moved either to more suitable beaches, or to hatcheries with artificial shading. Researchers have tested the use of synthetic shade cloth and found it is effective in reducing sand and nest temperatures.

Other potential strategies involve adding light-coloured sand on top of nests. This can help by absorbing less solar radiation (heat) compared to darker sand. Beach sprinklers have also been tested to simulate the cooling effect of rainfall.

The effectiveness of these actions has yet to be fully tested, but there is concern about some potential negative side effects. For example, excess water from sprinklers may cause fungal infections on eggs.

Finally, as much as mitigation measures are important, these are always short-term solutions. In the long run, prevention is always the best strategy, i.e. protecting the nesting beaches that currently produce more males from deforestation, development and habitat degradation.

Our recent research on the largest green turtle population in Africa reports unusually high male hatchling production. We found almost balanced hatchling sex ratios (1 female to 1.2 males). We attributed this mostly to the cooling effect of the native forest.

This, and similar nesting beaches, should be designated as priority conservation sites, as they will be key to ensuring the future of sea turtles under projected global warming scenarios.

Sea turtles are resilient creatures. They have been around for over 200 million years, surviving the mass extinction that included the dinosaurs, and enduring dramatic climatic changes in the past.

There is potential for these creatures to adapt, as they did before. This could be through, for example, shifting the timing of nesting to cooler periods, changing their distribution to more suitable habitats, or evolution of critical incubation temperatures that produce males.

But the climate today is changing at an unprecedented rate. Along with the feminisation of these turtles in the northern Great Barrier Reef, sea turtles globally face many threats from humans. These include problems associated with by-catch, poaching, habitat degradation and coastal development, plus a history of intense human exploitation.

In 2018, the prevalence of these species depends now more than ever on the effectiveness of conservation measures.

Great Barrier Reef: rising temperatures turning green sea turtles female

‘Complete feminisation’ of northern population is possible in near future, researchers find

Helen Davidson

Mon 8 Jan ‘18 17.00 GMTLast modified on Mon 8 Jan ‘18 22.00 GMT

Rising temperatures are turning almost all green sea turtles in a Great Barrier Reef population female, new research has found.

The scientific paper warned the skewed ratio could threaten the population’s future.

Sea turtles are among species with temperature dependent sex-determination and the proportion of female hatchlings increases when nests are in warmer sands.

Tuesday’s paper, from the National Oceanic and Atmospheric Administration, California State University and Worldwide Fund for Nature Australia, is published in Current Biology. It examined two genetically distinct populations of turtles on the reef, finding the northern group of about 200,000 animals was overwhelmingly female.

While the southern population was 65%-69% female, females in the northern group accounted for 99.1% of juveniles, 99.8% of subadults and 86.8% of adults.

“Combining our results with temperature data show that the northern GBR green turtle rookeries have been producing primarily females for more than two decades and that the complete feminisation of this population is possible in the near future,” the paper said.

The temperature at which the turtles will produce male or female hatchlings is heritable, the paper said, but tipped to produce 100% male or 100% female hatchlings within a range of just a few degrees.

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Has the Great Barrier Reef died? Not quite.

October 15, 2016

by Chuck Bednar 

Literary giant Mark Twain once said, “The reports of my death have been greatly exaggerated,” and according to scientists, the same is true when it comes to the 1,400-mile-long Great Barrier Reef in Australia – despite the recent publication of its obituary by Outside Online.

In that piece, author Rowan Jacobsen mourns the loss of the 25-million-year old community of coral reefs in the Pacific Ocean, which he referred to as “one of the most spectacular features on the planet,” to the effects of climate change and ocean acidification following “a long illness.”

“For most of its life, the reef was the world’s largest living structure, and the only one visible from space,” Jacobsen wrote in the piece. “In total area, it was larger than the United Kingdom, and it contained more biodiversity than all of Europe combined... [and] among its many other achievements, the reef was home to one of the world’s largest populations of dugong and the largest breeding ground of green turtles.”

Despite being declared a UNESCO World Heritage Site in 1981, he added, it experienced mass bleaching events regularly, and by the turn of the century, the waters surrounding it had become so acidic that they began to dissolve the reef itself. Ultimately, Jacobsen noted, it succumbed to these events – only, according to other scientists, the Reef isn’t quite dead yet.

‘Not too late’ to save the Reef, despite recent bleaching events

“It’s not too late for the Great Barrier Reef, and people who think that have a really profound misconception about what we know and don’t know about coral resilience,” Dr. Kim Cobb from the Georgia Tech School of Earth and Atmospheric Sciences told the Los Angeles Times Friday.

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Rare hybrid sea turtle released on the Great Barrier Reef – via Herp Digest

AAP 9/29/16

A rare hybrid turtle has been released back into the wild on the Great Barrier Reef after being nursed back to health at a Townsville aquarium.

The reptile, named Summer, is a cross between a green sea turtle and a hawksbill turtle - the first of its kind recorded in Australia.

Summer has just spent more than six months being cared for at the Reef HQ Great Barrier Reef Aquarium's turtle hospital.

She was nursed back to health after being found at the Port of Townsville with severe injuries from two fishing hooks lodged in her mouth.

Summer, thought to be between 15 and 20 years old, was released into waters at The Strand in Townsville this morning alongside a green turtle named Sofie.

Sofie was taken to the turtle hospital after she was found malnourished and lethargic by researchers at Cockle Bay, Magnetic Island.

Both reptiles recovered after being given a high protein diet, anti-parasite medication and low salinity baths.

Reef HQ Aquarium's director Fred Nucifora said while hybridisation was common in sea turtles, Summer's crossbreed was so rare that she was the only one of her kind recorded in Australian waters.

Despite her uniqueness Summer, like all other turtles cared for at the aquarium, will be released.

"Whilst it is rare and amazing, that's not a reason for wanting to keep her here on display," Mr Nucifora told AAP.

The turtle hospital has cared for more than 200 of the reptiles since opening seven years ago.