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.

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Three charts on: the incredible shrinking renewable energy job market


Paul Burke, Australian National University

This is the first piece in our new Three Charts series, in which we aim to highlight interesting trends in three simple charts. The Conversation

Australia is embarking on a transition from an electricity system that relies largely on coal to one that may one day be 100% renewable. Last week’s closure of the Hazelwood coal-fired generator was an important milestone on this path.

The development of the renewables sector has not, however, been a smooth ride.

Estimates released by the Australian Bureau of Statistics suggest that the number of direct full-time equivalent jobs in renewable energy activities has continued to fall from its 2011-12 peak. Over a period in which the Australian economy saw around 600,000 additional people get jobs, employment in the renewables sector has been going backwards.

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A small employer

The renewables sector is estimated to have directly provided only 11,150 full-time equivalent jobs in 2015-16. The Australian labour force exceeds 12.6 million people. The sector thus makes a small contribution to national employment, although one that is quite important in some local economies.

Around half of the jobs in renewables in 2015-16 were in installing (and maintaining) rooftop solar systems. Hydroelectricity generation provides 1,840 full-time equivalent jobs, a number that is likely to increase if pumped storage is to make a larger contribution to smoothing Australia’s electricity supply. Biomass provides 1,430 full-time jobs, and the wind industry around 620.

The fact that renewables is a small employer – especially once installations are up and running – is not a bad thing. If renewables were labour-intensive, they would be expensive.

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Up then down

The rise and then fall in renewables jobs is primarily a result of what has happened to installations of rooftop solar. The annual number of small-scale solar installations (PV and solar water heaters) skyrocketed over the four years to 2011. This rapid growth was spurred by generous feed-in-tariffs, rebates, and rules for federal government solar credits. There was also a national program to install solar panels on schools.

When these arrangements were curtailed, uptake fell. Annual installations of small-scale solar PV and water heaters are down by more than 60% from their peak. We are still installing a lot of new systems (more than 183,000 in 2016), but fewer than before. Employment estimates for small-scale solar closely track installation rates. The decline in employment in the wind energy sector is also worth noting.

The largest fall in renewables jobs has been in Queensland, a state that substantially tightened its feed-in-tariff scheme for rooftop solar in several steps from 2011 on. Queensland also holds the title of having Australia’s highest residential rooftop solar PV penetration rate (32%). South Australia is not far behind, at 31%.

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Ramping up large-scale renewables

Recent years of policy uncertainty and backtracking have not helped the rollout of large-scale renewables. The termination of Australia’s carbon price and downwards renegotiation of the Renewable Energy Target had chilling effects on investment.

Those events are now behind us. With continued reductions in the cost of renewables, brighter days for the sector appear to be ahead, especially if our governments get policy settings right.

We can expect particularly rapid growth in jobs installing large-scale solar PV. Just last week, for example, it was announced that South Australia is to have a large new solar farm.

Paul Burke, Fellow, Crawford School, Australian National University

This article was originally published on The Conversation. Read the original article.

Shrinking Antarctic glaciers could make Adélie penguins unlikely winners of climate change


Jane Younger, University of Tasmania

Penguin numbers exploded in East Antarctica at the end of the last ice age, according to research published today in BMC Evolutionary Biology. Despite their image as cold-loving creatures, the increase in Adélie penguin numbers seems to be closely linked to shrinking glaciers, raising the possibility the these penguins could be winners from current climate change.

Adélie penguins are one of only two penguin species that live on the Antarctic continent. Their cousins, emperor penguins, may be the movie stars, but it is the Adélies that are the bigger players in the Southern Ocean. They outnumber emperors by more than ten to one, with a population of over 7.5 million breeding adults and counting.

Given the abundance of Adélie penguins and their crucial role in Southern Ocean ecosystems, there has been a great deal of interest in understanding how the species is likely to respond to future climate change.

There are more then 7 million of these guys in Antarctica.
Jane Younger, Author provided

Sensitivity to sea ice

Breeding colonies have been monitored for decades to determine the effects of a changing environment on the penguins. A common finding of many of these studies is that Adélies are highly sensitive to sea ice conditions.

Unlike emperor penguins, Adélies do not nest on the sea ice, but they must cross it to reach their nests on land. As everyone knows, penguins are not the most efficient walkers, and in years with a lot of sea ice their journeys to and from the ocean to feed their chicks can become lengthy. With a longer wait between meals chicks are less likely to survive.

In an extreme case, extensive sea ice at one breeding colony had a devastating impact in 2014, and not a single chick survived.

Based on these observations over years and decades, there has been concern that changing sea ice conditions, including increases in certain parts of Antarctica, could have a serious impact on Adélie penguin numbers in the future.

Short-term vs long-term climate change

However, the climate change that is taking place now is not a decadal trend. Rather, the shrinking glaciers and ice sheets, changing sea ice conditions, and shifting currents and weather patterns represent a global change to a new climate.

We therefore set out to understand how Adélie penguins in East Antarctica were affected by the last big shift to a different climate: the ending of the last ice age.

Following similar methods to our previous study on emperor penguins, we used genetic data to uncover the trend of the Adélie population in East Antarctica over the past 22,000 years.

Researchers have been investigating penguins to see how they might respond to climate change.
Laura Morrissey, Author provided

The end of the ice age

We found that, as for the emperor penguins, Adélies were far less common during the ice age. This is not at all surprising since most of their nesting sites would have been covered with glaciers and their feeding grounds encased in sea ice that never melted.

Following the end of the ice age 20,000 years ago, temperatures increased slowly, and after a few thousand years of warming the glaciers and ice sheets began to shrink. Fast forward to 10,000 years ago and the annual sea ice melting cycle that we see today was established.

Given the sensitivity of Adélie penguins to sea ice changes today, we predicted that Adélie numbers would remain very small until 10,000 years ago when sea ice conditions became similar to what they are now.

However, the penguins surprised us again. We found that the number of Adélies exploded by around 135-fold, but the expansion pre-dated the sea ice change by at least 3000 years.

Penguin numbers exploded at the end of the last ice age.
Jane Younger, Author provided

Shrinking glaciers

The proliferation of Adélie penguins in East Antarctica began during a period of ice sheet and glacier retreat, which would have increased the amount of ice-free ground available for nesting.

A study of Adélie penguins at the Scotia Arc, on the opposite side of the continent, found that numbers in this region rose 17,000 years ago. That expansion was several thousand years before the growth of the East Antarctic population, but coincided with the shrinking of glaciers in the Scotia Arc. This lends further support to our conclusion that it was glacier retreat, rather than changing sea ice conditions, that caused the hike in Adélie penguin numbers after the last ice age.

This is an important finding, as it suggests that the effects of climate change on a species over thousands of years can be quite different to the effects over years or decades. Given the long-term nature of contemporary climate change, we suggest that it is critical to consider millennial-scale trends alongside decadal ecological studies when predicting the effects of climate change on a species.

Could penguins benefit from future climate change?

Glaciers and ice sheets in Antarctica will continue to shrink. As this happens, ground that was previously covered in ice will become suitable for Adélie penguin nesting. In regions with adequate food supplies and where sea ice conditions remain favourable, Adélie penguin numbers may continue to grow.

A recent study using satellite images showed that one breeding colony in the Ross Sea grew by 84% between 1983 and 2010, as a direct result of a glacier shrinking by 543 m and uncovering new nesting sites.

While it seems that East Antarctic Adélie penguins might come out on top as climate change winners, it is important to keep in mind that for penguins to flourish their food supplies must be plentiful enough to meet the demands of a growing population. Whether this will be the case in the future remains to be seen, as Adélie penguin prey species, such as Antarctic krill, are threatened by both climate change and commercial fisheries.

The Conversation

Jane Younger, Postdoctoral research fellow, University of Tasmania

This article was originally published on The Conversation. Read the original article.

Article: Climate Change Shrinking Fish


The link below is to an article that reports on another threat to the environment caused by climate change – shrinking fish.

For more visit:
http://www.bbc.co.uk/news/science-environment-19758440