Daily Bulletin


The Conversation

  • Written by The Conversation Contributor

A new experiment on the Great Barrier Reef has shown, for the first time, that ocean acidification is already harming the growth of coral reefs in their natural setting.

As our research published in Nature today shows, the reduction in seawater pH – caused by carbon dioxide from human activities such as burning fossil fuels – is making it more difficult for corals to build and maintain their skeletons.

We and our colleagues, led by Rebecca Albright and Ken Calderia from the Carnegie Institution for Science in Stanford, California, carried out the first experimental manipulation of seawater chemistry in a natural coral reef ecosystem. Previous climate change studies on coral reefs have been done either in the laboratory or in closed-system tanks on the reef.

image One Tree Island forms a naturally isolated lagoon where pH levels can be manipulated. One Tree Island Research Station/University of Sydney/Nature

Coral reefs are particularly vulnerable to ocean acidification because calcium carbonate, the mineral building blocks of their skeletons, dissolves easily in acid. Below a certain pH, this dissolution is predicted to outweigh the accumulation of new calcium carbonate that allows reefs to grow and to recover from erosion processes such as storms.

Previous studies have shown large-scale declines in coral reefs over recent decades. Rates of reef calcification were 40% lower in 2008-09 than in 1975-76.

However, it was hard to pinpoint exactly how much of the decline was due to acidification, and how much was caused by other human-induced stresses such as ocean warming, pollution and overfishing. Understanding this is essential to predicting how coral reefs may fare in the face of continued global climate change.

image The study used pink dye to track the movement of the experimental seawater. Rebecca Albright/Nature

To answer this question, we manipulated the pH of seawater flowing over a reef flat at One Tree Island in the southern Great Barrier Reef. By adding sodium hydroxide (an alkali), we brought the reef’s pH closer to levels estimated for pre-industrial times, based on estimates of atmospheric carbon dioxide from that era. In doing so, we pushed the reef “back in time”, to find out how fast it would have been growing before human-induced acidification began.

It was clear from our results that reef calcification was around 7% higher under pre-industrial conditions than those experienced today.

Most other ocean acidification experiments manipulate seawater conditions based on the low pH levels predicted for coming decades, to understand the potential effects of future ocean conditions. But we have shown that present-day conditions are already taking their toll on corals.

As Albright explains:

Our work provides the first strong evidence from experiments on a natural ecosystem that ocean acidification is already causing reefs to grow more slowly than they did 100 years ago. Ocean acidification is already taking its toll on coral reef communities. This is no longer a fear for the future; it is the reality of today.

With greenhouse gas emissions continuing to rise, our results suggest a bleak future for coral reefs over the coming decades, with reduced calcification and increased dissolution. This is particularly concerning in light of the major coral bleaching events observed globally over the past few years amid prolonged high sea surface temperatures. The mixed effects of ocean warming and acidification, as well as other human-induced and natural stressors, pose serious threats to the ecosystems we know today.

Increasing the alkalinity of ocean water around coral reefs has been proposed as a geoengineering measure to save shallow marine ecosystems. Our results suggest that this could be effective in isolated areas, but implementing such measures at large scales would be almost impossible.

As our colleague Ken Caldeira has pointed out, the only real and lasting solution is to make deep, rapid cuts in our carbon dioxide emissions. Otherwise the next century could be one without coral reefs.

Kennedy Wolfe will be online to answer questions about this research from 11.30 am to 12.30 pm AEDT on Thursday February 25. Leave your comments below.

Authors: The Conversation Contributor

Read more http://theconversation.com/ocean-acidification-is-already-harming-the-great-barrier-reefs-growth-55226

Writers Wanted

COVID has left Australia's biomedical research sector gasping for air

arrow_forward

How Australian vice-chancellors' pay came to average $1 million and why it's a problem

arrow_forward

The Conversation
INTERWEBS DIGITAL AGENCY

Politics

Prime Minister Interview with Ben Fordham, 2GB

BEN FORDHAM: Scott Morrison, good morning to you.    PRIME MINISTER: Good morning, Ben. How are you?    FORDHAM: Good. How many days have you got to go?   PRIME MINISTER: I've got another we...

Scott Morrison - avatar Scott Morrison

Prime Minister Interview with Kieran Gilbert, Sky News

KIERAN GILBERT: Kieran Gilbert here with you and the Prime Minister joins me. Prime Minister, thanks so much for your time.  PRIME MINISTER: G'day Kieran.  GILBERT: An assumption a vaccine is ...

Daily Bulletin - avatar Daily Bulletin

Did BLM Really Change the US Police Work?

The Black Lives Matter (BLM) movement has proven that the power of the state rests in the hands of the people it governs. Following the death of 46-year-old black American George Floyd in a case of ...

a Guest Writer - avatar a Guest Writer

Business News

Nisbets’ Collab with The Lobby is Showing the Sexy Side of Hospitality Supply

Hospitality supply services might not immediately make you think ‘sexy’. But when a barkeep in a moodily lit bar holds up the perfectly formed juniper gin balloon or catches the light in the edg...

The Atticism - avatar The Atticism

Buy Instagram Followers And Likes Now

Do you like to buy followers on Instagram? Just give a simple Google search on the internet, and there will be an abounding of seeking outcomes full of businesses offering such services. But, th...

News Co - avatar News Co

Cybersecurity data means nothing to business leaders without context

Top business leaders are starting to realise the widespread impact a cyberattack can have on a business. Unfortunately, according to a study by Forrester Consulting commissioned by Tenable, some...

Scott McKinnel, ANZ Country Manager, Tenable - avatar Scott McKinnel, ANZ Country Manager, Tenable



News Co Media Group

Content & Technology Connecting Global Audiences

More Information - Less Opinion