acidifying

Coral Reefs And Fish Survival | Earth Wise

August 25, 2021 By EarthWise Leave a Comment

The precarious state of the world’s coral reefs has been a highly visible subject for a decade or more. Mostly what we hear about is the loss of some of the most beautiful sights on the planet. But there is far more at stake than scenic wonders.

The warming and acidifying of ocean waters are causing corals to increasingly bleach and often die. Corals provide a unique food source for some species of fish and a three-dimensional habitat for many others. The fish that depend on corals are often prey for fish that don’t depend directly on corals and so on up the food chain.

What happens to fish when coral reefs disappear? The fish species that feed on corals will starve while others will seek alternative rocky habitats.

A new study by the University of Helsinki uses statistical methods to predict how fish diversity will respond to declines in coral diversity. It concludes that a future coral loss might cause a 40% reduction in reef fish diversity globally. This is more than a loss of colorful sights for snorkelers; reef fishes provide essential protein for millions of people around the world.

The estimate of potential loss of fish species greatly exceeds the number of species known to depend directly or even indirectly on coral. The implication is that coral reef food webs will begin to unravel if corals go extinct. This unraveling is expected to be worse in some places than others. The Central Pacific, for example, could lose 60% of its reef fish.

For both snorkelers and for the millions who depend upon reef fishes for food, the need for greater efforts to conserve and restore coral reefs is apparent.

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A future ocean that is too warm for corals might have half as many fish species

Photo, posted September 27, 2009, courtesy of Matt Kieffer via Flickr.

Earth Wise is a production of WAMC Northeast Public Radio.

A Devastating Threat To Coral Reef Habitats | Earth Wise

March 25, 2020 By EarthWise 2 Comments

According to new research from scientists at the University of Hawaii Manoa, the warming and acidifying oceans could wipe out nearly all existing coral reef habitats by 2100. In fact, the researchers predict that 70-90% of coral reefs will disappear over the next 20 years alone as a consequence of climate change and pollution.

Some organizations are attempting to save coral habitats by transplanting live corals from labs to reefs. The idea is that the new young corals will help revive the reefs. But after mapping where such restoration efforts would be most successful, the research indicates that there will be little to no suitable habitat remaining for corals by 2100. Small portions of Baja California and the Red Sea are two of the sites that could remain viable by 2100, although neither are ideal due to their proximity to rivers. Sea surfaces temperature and acidity are two of the most important factors in determining the viability of a site for restoration.

Warming ocean waters stress corals, which cause them to expel the symbiotic algae living inside them. This turns the often colorful corals white – an event known as coral bleaching. Bleached corals are not dead corals, but they are at a higher risk of dying. These coral bleaching events are becoming more frequent as a result of the changing climate.

The projected increases in human pollution will only play a minor role in the future elimination of coral reef habitats. Ironically, that’s because humans have already caused such extensive damage to coral reefs that there aren’t many locations left to impact.

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Warming, acidic oceans may nearly eliminate coral reef habitats by 2100

Photo, posted September 28, 2009, courtesy of Matt Kieffer via Flickr.

Earth Wise is a production of WAMC Northeast Public Radio.

Community Action And Coral Reefs

January 1, 2020 By EarthWise Leave a Comment

Coral reef habitats are some of the densest and most varied ecosystems on earth. While coral reefs cover just 0.2% of the ocean floor, scientists estimate that nearly one million different species of fish, invertebrates, and algae can be found in or around coral reefs.

However, climate change is wreaking havoc on the health of coral reefs. Warming and acidifying oceans are resulting in enormous coral losses. Overfishing, development, and pollution are also threatening coral reef health.

According to new research, positive community action can help boost fish populations in coral reefs and safeguard future fish numbers. The paper, which was recently published in the journal Proceedings of the National Academy of Sciences, details the social and ecological outcomes of work being done in Papua New Guinea since 2001.

These communities have established a traditional system of rotational fishing closures in order to manage their fisheries resources. They ban fishing on part of their reefs for a few years, and then open these closures when village elders believe fish behavior has changed and fish populations have recovered. They then close a different part of their reefs, and repeat the process.

The researchers found that these rotational practices resulted in more than twice as many fish on the closed reefs as compared to open ones, and the closures made fish less scared of people and easier to catch. But the researchers did caution that this short term boost in fish numbers may not be enough to stop the overall impact of fishing.

Globally, more than 500 million people depend on coral reefs for food, income, and coastal protection. Balancing community needs with environmental needs can be tricky business.

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Positive community action can help coral reef health

Photo, posted October 11, 2011, courtesy of Paul Toogood 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.

A Small Win For Coral

August 15, 2018 By EarthWise Leave a Comment

The Belize Barrier Reef is the largest barrier reef system in the Northern Hemisphere. It extends roughly 200 miles, and is made up of a series of coral reefs, cays and islands, many of which are covered with mangroves. It was designated a Unesco World Heritage Site in 1996, and added to its endangered list in 2009.