Acid oceans are shrinking plankton, fuelling faster climate change



Researchers investigated how acidic oceans affect plankton in Prydz Bay, East Antarctica.
Daniel A. Nielsen, Author provided

Katherina Petrou, University of Technology Sydney and Daniel Nielsen, University of Technology Sydney

Increasingly acidic oceans are putting algae at risk, threatening the foundation of the entire marine food web.

Our research into the effects of CO₂-induced changes to microscopic ocean algae – called phytoplankton – was published today in Nature Climate Change. It has uncovered a previously unrecognised threat from ocean acidification.

In our study we discovered increased seawater acidity reduced Antarctic phytoplanktons’ ability to build strong cell walls, making them smaller and less effective at storing carbon. At current rates of seawater acidification, we could see this effect before the end of the century.




Read more:
Ocean acidification is already harming the Great Barrier Reef’s growth


What is ocean acidification?

Carbon dioxide emissions are not just altering our atmosphere. More than 40% of CO₂ emitted by people is absorbed by our oceans.

While reducing the CO₂ in our atmosphere is generally a good thing, the ugly consequence is this process makes seawater more acidic. Just as placing a tooth in a jar of cola will (eventually) dissolve it, increasingly acidic seawater has a devastating effect on organisms that build their bodies out of calcium, like corals and shellfish.

Many studies to date have therefore taken the perfectly logical step of studying the effects of seawater acidification on these “calcifying” creatures. However, we wanted to know if other, non-calcifying, species are at risk.

Diatoms in our oceans

Phytoplankton use photosynthesis to turn carbon in the atmosphere into carbon in their bodies. We looked at diatoms, a key group of phytoplankton responsible for 40% of this process in the ocean. Not only do they remove huge amounts of carbon, they also fuel entire marine food webs.

Diatoms use dissolved silica to build the walls of their cells. These dense, glass-like structures mean diatoms sink more quickly than other phytoplankton and therefore increase the transfer of carbon to the sea floor where it may be stored for millennia.

Diatoms are microscopic plant plankton that collectively remove huge amounts of carbon from the atmosphere.
Alyce M. Hancock, Author provided

This makes diatoms major players in the global carbon cycle. That’s why our team decided to look at how climate-change-driven ocean acidification might affect this process.

We exposed a natural Antarctic phytoplankton community to increasing levels of acidity. We then measured the rate at which the whole community used dissolved silica to build their cells, as well as the rates of individual species within the community.

More acid means less silicone

The more acidic the seawater, the more the diatom communities were made up of smaller species, reducing the total amount of silica they produced. Less silica means the diatoms aren’t heavy enough to sink quickly, reducing the rate at which they float down to the sea bed, safely storing carbon away from the atmosphere.

On examining individual cells, we found many of the species were highly sensitive to increased acidity, reducing their individual silicification rates by 35-80%. These results revealed not only are communities changing, but species that remain in the community are building less-dense cell walls.

Most alarming, many of the species were affected at ocean pH levels predicted for the end of this century, adding to a growing body of evidence showing significant ecological implications of climate change will take effect much sooner than previously anticipated.

Marine diversity is in decline

These losses in silica production could have far reaching consequences for the biology and chemistry of our oceans.

Many species affected are also an important component of the diet of the Antarctic krill, which is central to the Antarctic marine food web.

Fewer diatoms sinking to the ocean floor mean significant changes in silicon cycling and carbon burial. In a time when carbon drawn down by our ocean is crucial to helping sustain our atmospheric systems, any loss from this process will exacerbate CO₂ pollution.

Our new research adds yet another group of organisms to the list of climate change casualties. It emphasises the urgent need to reduce our dependency on fossil fuels.




Read more:
Our acid oceans will dissolve coral reef sands within decades


The only course of action to prevent catastrophic climate change is to stop emitting CO₂. We need to cut our emissions soon, if we hope to keep our oceans from becoming too acidic to sustain healthy marine ecosystems.The Conversation

Katherina Petrou, Senior Lecturer in Phytoplankton Ecophysiology, University of Technology Sydney and Daniel Nielsen, Casual Academic, University of Technology Sydney

This article is republished from The Conversation under a Creative Commons license. Read the original article.

Paddling blind: why we urgently need a water audit



There’s broad support from communities and farmers for proper water audits.
John/Flickr, CC BY-SA

Quentin Grafton, Crawford School of Public Policy, Australian National University and John Williams, Australian National University

In the wake of a damning royal commission and an ABC Four Corners investigation, the federal government has created an Inspector General for the Murray-Darling Basin, to combat water theft, ensure water recovery and efficiency projects are delivered properly, and essentially make sure everyone is acting as they should.

While this is a laudable aim, the Inspector General – currently former Australian Federal Police Commissioner Mike Keelty – cannot hope to do this job without knowing how much water is being used in the Basin, by whom it is used, and where.




Read more:
Billions spent on Murray-Darling water infrastructure: here’s the result


This might seem like basic information, but the Bureau of Meteorology, the Murray-Darling Basin Authority and state water accounts are not up to the task.

We urgently need a comprehensive audit to track the water in the Murray Darling Basin, so Inspector General Keelty can effectively investigate what he has already described as a “river ripe for corruption”.

Up the creek

Back in 2004 all governments in Australia agreed to track and provide information on water in terms of planning, monitoring, trading, environmental management, and on-farm management.

But water accounts still lack many essential features including double-entry accounting. When applied to water, double-entry accounts means that when one person consumes more water, someone else must consume less.




Read more:
Aboriginal voices are missing from the Murray-Darling Basin crisis


The technology to track this already exists: satellites that can quantify surface water are successfully being used used in the United States.

If we had monthly water consumption measurements, we could see how much water is being used, by whom, when and where. This would help decision makers see problems before they emerge, such as the mass fish deaths in the Darling River, and respond in real time.

As a recent report from the Natural Resources Commission shows, without proper accounting, too much water is taken upstream – seriously harming downstream communities.

Wide support for an audit

An independent Basin-wide water audit is supported by communities and some irrigators.

In July NSW farmers voted in support of a federal royal commission into “the failings of the Murray Darling Basin Plan”. In our view, this vote shows many farmers support much greater transparency about how much water is being consumed, and by whom.




Read more:
The Darling River is simply not supposed to dry out, even in drought


Double-entry water consumption accounts would help identify whether the billions of dollars planned in subsidies to increase irrigation efficiency will actually deliver value for money. But irrigation improvements only generate public benefits when more water is left or returns to flow in streams and rivers. Such flows are essential to healthy rivers and sustainable Basin communities.

Irrigators’ crops benefit from increased efficiency, so subsidies help farmers greatly – but it is very unclear whether they do anything for the public good. In fact, they seem to reduce the amount of water that finds its way back into the rivers. Research also shows infrastructure subsidies to improve irrigation efficiency typically increases water consumption at the Basin level.

Our research, published earlier this year in the Australasian Journal of Water Resources shows federal irrigation infrastructure subsidies may have reduced net stream and river levels. This is even after accounting for the water entitlements irrigators provided to the government in exchange for these subsidies.




Read more:
5 ways the government can clean up the Murray-Darling Basin Plan


Independent audits

Just like financial accounts, water accounts must be independently audited.

For the average taxpayer, who has to justify every dollar they get from the government, it’s hard to imagine how some corporations can be given millions of dollars in subsidies without actual measurements (before and after) of the claimed water savings.

If Newstart recipients need to report and manage their income and have a job plan, as part of a system of appropriate checks and balances, shouldn’t the Australian government also be checking whether billions spent on subsidies for irrigators actually saves water?




Read more:
The Murray-Darling Basin scandal: economists have seen it coming for decades


A water audit would cost less than 1% of the money already spent on water infrastructure subsidies in the Basin. Unlike irrigation infrastructure subsidies, a water audit is value for money.

Importantly, independent water consumption accounts would allow the Inspector General for the Murray-Darling Basin to effectively manage our most critical nature resource, water.The Conversation

Quentin Grafton, Director of the Centre for Water Economics, Environment and Policy, Crawford School of Public Policy, Australian National University and John Williams, Adjunct Professor Environment and Natural Resources, Crawford School of Public Policy, Australian National University

This article is republished from The Conversation under a Creative Commons license. Read the original article.