bleaching

Climate Change And Dolphins

May 27, 2019 By EarthWise Leave a Comment

We don’t think of heatwaves as something that affects the ocean, but increasingly, as the planet warms, there have been instances where ocean water temperatures become much higher than normal for extended periods of time. There has been much discussion of this phenomenon with regard to coral reefs where the catastrophic rise in coral bleaching events has been the result.

Recently, a study at the University of Zurich looked at the effects of ocean heatwaves on marine life higher in the food chain. They studied the well-known dolphin population in Shark Bay, Western Australia.

In early 2011, a heatwave caused water temperatures in Shark Bay to rise more than 4 degrees above the annual average for an extended period. This led to a substantial loss of seagrass, which is a driving factor in the Shark Bay ecosystem.

The researchers investigated how this environmental damage affected survival and reproduction of dolphins, using long-term data on hundreds of animals collected over a ten-year period from 2007 to 2017.

Their analysis showed that dolphins’ survival rate dropped by 12% and female dolphins were giving birth to fewer calves. That phenomenon that began in 2011 lasted at least until 2017.

The researchers were surprised by the extent and the duration of the influence of the heatwave, especially the fact that the reproductive rate of dolphins had not returned to normal even after 6 years.

This study shows for the first time that marine heatwaves not only affect organisms at the lower levels of the food chain, but also might have considerable long-term consequences for the animals at the top, such as dolphins.

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Climate change is a threat to dolphins’ survival

Photo, posted December 14, 2014, courtesy of Ed Dunens via Flickr.

Earth Wise is a production of WAMC Northeast Public Radio.

Another Problem For Coral Reefs

April 5, 2019 By EarthWise Leave a Comment

Coral reefs around the world have been suffering in recent years from warming ocean temperatures as well as from increasing ocean acidification. Corals are very sensitive organisms that can only tolerate relatively slight changes in their environment. Thus, the majority of reef-building corals are found in tropical and subtropical waters with favorable conditions.

New research has confirmed that drastic changes in ocean salinity from, for example, severe freshwater flooding, provoke similar stress responses in corals as the heating that has resulted in freshwater bleaching and, eventually, coral death.

The coast of northeast Queensland in Australia has experienced abnormal monsoon-related freshwater flooding that caused extreme and sudden changes in the ocean salt concentration. In places, nearshore reefs were exposed to water with only half the normal ocean salinity. The result has been a shock response in corals that prevents normal cell function. Unlike their response to heat stress, corals exposed to reduced salinity experience a complete collapse of their internal cellular protein balance.

The central Great Barrier Reef has actually been relatively free from mass thermal bleaching events this Australian summer, but many coastal reefs instead have been battling dramatic changes in water conditions as a result of massive plumes of floodwater.

The wild weather in Australia is undoubtedly associated with the changing climate and this new research shows that it is leading to yet another threat to the world’s coral reefs. With the frequency and severity of heavy rainfall and runoff events predicted to continue to increase over the next few decades, proactive measures to increase the resiliency of coral reefs are needed more than ever.

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Reduced salinity of seawater wreaks havoc on coral chemistry

Photo, posted December 12, 2010, courtesy of Gareth Williams via Flickr.

Earth Wise is a production of WAMC Northeast Public Radio.

Disease On Coral Reefs

February 19, 2019 By EarthWise Leave a Comment

The warming oceans have led to bleaching events in coral reefs around the world, but bleaching is not the only problem corals face. Disease outbreaks are also becoming more frequent, severe, and widespread.

Many factors are contributing to the problem, including pollution and nitrogen runoff from fertilizers and coastal sewer and septic systems. However, the key culprit is likely the steadily increasing ocean temperatures, which are the cause of coral bleaching. Elevated water temperatures can cause coral polyps to expel the algae that sustains them and gives them color.

According to scientists, bleaching makes corals more susceptible to illness. In the Caribbean, a coral disease hotspot, about 80% of coral cover has disappeared, largely from outbreaks of “white band disease”, so called because of a white band of dead tissue that forms in affected corals. Two crucial reef-building species, elkhorn and staghorn coral, are now nearing extinction in the regions. The reef extending along the Florida coastline is the third largest reef ecosystem in the world and nearly 35% of it has been lost to disease.

Estimates are that disease outbreaks have wiped out at least 6% of the corals on the Great Barrier Reef in Australia. In that region, diseases are more prevalent in areas where corals were damaged by fishing and other human activity because wounded coral provides an entry point for pathogens and bacteria.

In the face of climate change and mounting disease outbreaks, scientists are scrambling for solutions to stave off catastrophe. Assisting the migration of hardier coral species and breeding so-called “super corals” are among the strategies being pursued. It is unknown whether these and other forms of intervention can be used on a wide enough scale to really make a difference.

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As Disease Ravages Coral Reefs, Scientists Scramble for Solutions

Photo, posted November 29, 2012, courtesy of Robert Linsdell via Flickr.

Earth Wise is a production of WAMC Northeast Public Radio.

Is There Hope For Coral Reefs?

January 16, 2019 By EarthWise Leave a Comment

News about the world’s coral reefs has been relentlessly bad for a number of years. Warming, acidifying oceans have wreaked havoc with coral reefs leading to enormous losses. Nowhere have things been more dire than in Australia’s Great Barrier Reef. Coral bleaching events have been increasingly common and severe over the past two decades. In fact, only 7% of the Great Barrier Reef has escaped bleaching entirely since 1998.

While the future of the world’s coral reefs is very much uncertain as global heating continues, there is a recent bit of hopeful news. According to a study published in Nature Climate Change, the response of the Great Barrier Reef to the extreme temperatures in 2017 was quite different from that of the previous year in the aftermath of back-to-back bouts of coral bleaching.

Surprisingly, corals that bleached in 2016 but managed to survive were more resistant to the recurrence of hot conditions in 2017.

Many corals don’t survive bleaching events at all and, of course,those corals don’t bleach for a second time. But the surviving corals from the 2016 bleaching event were tougher species. As a result of bleaching, the mix of coral species on the reef is changing very rapidly. The net result was that there was less bleaching in 2017 even though the temperatures that year were even more extreme than in 2016.

There have now been four mass bleaching events on the Great Barrier Reef over the past 20 years and it is only a matter of time before another one occurs triggered by the next marine heatwave. Almost half of the corals on the northern two-thirds of the reef have been killed. But at least some of the reef is showing impressive survival skills.

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A glimmer of hope for the world’s coral reefs

Photo, posted November 29, 2012, courtesy of Robert Linsdell via Flickr.

Earth Wise is a production of WAMC Northeast Public Radio.

Coral Nurseries

July 9, 2018 By EarthWise Leave a Comment

In the past, coral conservationists focused their efforts on protecting reefs from direct environmental threats such as land-based pollution and damaging fishing practices. These efforts continue, but as coral reefs face increasingly dire threats, conservationists are turning toward more proactive approaches.

[Read more…] about Coral Nurseries

Protecting Reefs Of Hope

June 4, 2018 By EarthWise Leave a Comment

One of the most harmful effects of the changing climate is what is happening to coral reefs. Warmer ocean temperatures and acidification are causing widespread bleaching of coral. Stressed corals expel the algae living in their tissue, turning the corals white and robbing them of nutrients. When bleaching events persist, the corals starve and die. Reefs everywhere have been experiencing mass bleaching events in recent years with over 70% of the coral reefs around the world being damaged.

A Philippine Coral Reef Survives

January 2, 2018 By EarthWise Leave a Comment

One of the greatest coral reef ecosystems in the world, the Tubbataha Reef in the Philippines, continues to prosper. Undersea coral walls that plunge more than 300 feet deep are home to some 600 species of fish and 360 kinds of coral, about half of all known species. According to experts, the ocean wilderness of Tubbataha Reef is about the closest thing to a true natural state for any reef in the world.

Genetic Engineering And Conservation

September 8, 2017 By EarthWise

Genetic engineering, or equivalently synthetic biology, is a multi-billion-dollar enterprise involved in pharmaceuticals, chemicals, biofuels and, of course, agriculture. In these fields, it is already the source of a great deal of controversy. But there is increasing interest in using synthetic biology (or synbio) technology as a tool for protecting the natural world, which is a prospect some find tantalizing and others find absolutely terrifying.

Can The Great Barrier Reef Be Saved?

August 17, 2017 By EarthWise

There have been many stories in the media about the ongoing environmental crisis at Australia’s Great Barrier Reef. Over the past two years, the reef has lost almost half of its coral because of bleaching events. Faced with this situation, the Australian government created the Reef 2050 Plan, a strategy to protect and maintain the reef through the year 2050.

Could Coral Reefs Be Wiped Out?

August 8, 2017 By EarthWise

A new study warns that coral reefs are in danger of disappearing forever. According to U.N. research, the world’s coral reefs could die out completely by mid-century unless carbon emissions are reduced enough to slow ocean warming.

Threats To Coral Reefs

May 12, 2017 By EarthWise

There has been much news recently about the growing bleaching events going on in the world’s coral reefs associated with ocean warming and acidification. The massive damage to Australia’s Great Barrier Reef is an ongoing tragedy.

The Great Barrier Reef

April 27, 2017 By EarthWise

According to a new paper published in the journal Nature, global warming has damaged huge sections of Australia’s Great Barrier Reef. The authors of the paper warn that the resilience of the reef – which is the world’s largest living structure – is waning rapidly.

Some Good News For Coral Reefs

August 12, 2016 By WAMC WEB

Most recent news about coral reefs around the world has been bad news. There has been unprecedented coral bleaching in places like Australia’s Great Barrier Reef. The effects of climate change – including warming temperatures and rising seas – as well as the recent El Niño event have led to damaged reefs across the globe.