Atmospheric CO2 reaches 400 ppm

In May 2013 the National Oceanic and Atmospheric Administration in the USA reported that the atmospheric concentration of CO2 at one of their recording stations topped 400 ppm for the first time. The media surrounding this event seems to have been very much based around the event itself with little comment on what it may mean. I find this moderately disappointing because we can be moderately confident of one thing  – increased CO2 in the atmosphere means that more will dissolve into the ocean, which means an increase in ocean acidification (this is classical chemistry!).

Despite the recent efforts of some of the worlds best scientists, both here in Australia and overseas, we still have an incomplete picture of the likely biological and ecological effects of this ocean acidification. However, we can be fairly certain of two things:

1. Ocean acidification will have negative impacts on organisms which form calcareous structures like the shells of molluscs (see pictures below) and the skeletons of corals; and

2. We are becoming increasingly aware that the increase in CO2 as a resource will cause changes to systems that are dominated by primary producers like seagrass and algae (e.g. kelp), mostly for the worse (for a starting point you could look at my webpage, but contact me for more information if you want!).

Unfortunately, as we enter a time of uncertainty for science funding in Australia, we may not develop a complete understanding of the system-wide effects of ocean acidification until it’s too late.

The growing edge of a juvenile abalone under high atmospheric CO2 (ultra-high magnification). Photo: Owen Burnell

The growing edge of a juvenile abalone under high atmospheric CO2 (ultra-high magnification). Photo: Owen Burnell

The growing edge of a juvenile abalone under normal atmospheric CO2 (ultra-high magnification)

The growing edge of a juvenile abalone under normal atmospheric CO2 (ultra-high magnification)


Coral reef structures resistant to Ocean Acidification

Coral reefs are structurally complex and "cemented" together by Crustose Coralline Algae.

Coral reefs are structurally complex and “cemented” together by Crustose Coralline Algae.

Unlike some of the media coverage, I’m not saying that coral reefs will be resistant to ocean acidification, and I’m certainly not saying that corals will be. There is some good news for the gloom of ocean acidification. Yet, the devil is in the detail!

Unknown to most people, Crustose Coralline Algae (known in the field as CCA to stop us tripping over the long name) are the pink algae which cement together the matrix of coral reefs the world over, effectively solidifying the structure that we know as “coral” reefs. These CCAs also form a dense, concrete like ridge on the exposed side of most reefs, protecting the more fragile corals from destructive wave energy. So, from a reef perspective they are very important.

Until now, most of the research into the future of CCAs under ocean acidification has demonstrated that they are likely to dissolve (e.g. Tropical species and temperate species). However, some colleagues and I have recently discovered two important things about these CCAs, (1) that they contain dolomite, a rather robust mineral that most people associate with mountains in Italy; and (2) that dolomite is quite resistant to pH which we are expecting in the world’s oceans in the next 100 years (link to the paper here).

What does this mean? Unfortunately it doesn’t mean that the world’s coral reefs are going to be saved from ocean acidification by dolomite-rich CCA. By all accounts the corals are still in trouble (though I still have my hopes for more adaptive capacity than we give them credit for!). However, there is some hope, because these CCA are likely to maintain their structure and thus continue to protect reefs from damage by waves.

A systems perspective of the future


Experiments show that some clownfish may not be able to smell their predators in the future

To understand how complex ecosystems function, and how things will change if we push them too hard (and we’re constantly pushing!), we humans need to break them down into simple parts. I’m not going to tell you that we shouldn’t do this, because we need to start somewhere, and I’ve certainly done it myself. Where we go wrong, however, is by not putting the parts back together again to try and understand how the entire system may work, ultimately giving us a very simple view of how the world works. But, every now and then we are reminded in stunning detail how failing to build up again will provide us with the wrong information.

My research group recently had one of these stunning moments when we were visited by Prof. Phil Munday from James Cook University. His research is primarily concerned with how ocean acidification will impact on fish and their various roles in the functioning of ecosystems. Basically, he shattered our thoughts about ocean acidification by teaching us that 1 + 1 does not equal 2!

In an elegant series of experiments, Phil’s research group has shown that if you look at the separate responses of predatory fish and their prey to ocean acidification you may not accurately predict the outcomes. For example, under near-future ocean acidification, clownfish (Amphiprion percula) are unable to recognise the smell of their predators. Even worse, some species of fish became almost suicidal, being attracted to the smell of their predator!

If you were to take this on face value you would think that these results mean that small fish are going to have increased mortality under future ocean conditions. However, Phil has shown that it’s not that straight forward because when predatory fish are also exposed to ocean acidification their prey preference can change; preferred prey under current conditions are the less preferred prey under future conditions.

What does this tell us? Apart from the fact that some fish are going to get lucky, I think the big point here is that we cannot simply add up the results of a number of simple experiments looking at individual system components and identify what will happen to systems overall. Just like unexpected synergies among different stressors, we can’t assume that adding up the components will be enough. It’s time to take a more system-oriented approach where we can!

Geoengineering – can we really fix it?

Crustose Coralline Algae growing on the rock under a juvenile kelp (Ecklonia radiata). CCA can cover up to 80% of the rock surface in the temperate waters of Australia and is essential for the settlement of many species.
Photo: Dr Andrew Irving.

A student emailed me yesterday to request a letter that I wrote to the editors of Science a couple of years ago (“Honing the geoengineering strategy“). At the time, I was incensed by talk that we could stop global warming by dumping tonnes of sulphur into the atmosphere (which has a cooling effect) or a range of other “engineering” solutions. There is a series of excellent reports published by the UK Royal Society on the topic for anyone who is interested.

It wasn’t the ridiculous nature of these suggestions that got my attention though. I was more concerned by two things:

1. Anything that we do other than cutting carbon emissions is only buying time and I believe will only give us a false sense of security; and

2. The disregard that many geoengineering solutions have for the other effects of pumping millions of tonnes of CO2 into the atmosphere (but note, not all geoengineering fits into this category – something I will post on later).

Yes, there is warming, but from an ocean’s perspective there is also Ocean Acidification. Whether you believe in “Climate Change” or not, ocean acidification is happening and will continue to happen – its basic chemistry. As carbon dioxide dissolves into seawater it forms carbonic acid, which in turn reduces the pH of the water. Now, the ocean won’t become acidic like the acid you find in car batteries, but this increased acidity does reduce the amount of carbonate in the water. This carbonate is essential for all of the organisms that form hard structures from calcium carbonate, including everything from corals to snails to crustose coralline algae.

I’m sure that everyone reading this will have heard about the corals, but who really cares about coralline algae (or CCAs as we term them)? In fact, do you know what they are? (the pink algae covering the rock in the picture above). Though they may be humble, thousands of species rely on them. In tropical systems they form a hard reef crest to protect corals from waves. In temperate kelp forests they are essential for the settlement of species like abalone, which are not only important to the ecosystem but support multi-million dollar fishing industries.

So, not only does the talk of geoengineering provide us with a false sense of security about our ability to treat the symptoms of climate change, but the discussion often disregards the multifaceted problems that are caused by excess carbon in our atmosphere. Ultimately, the only way to fix the problem is to treat the cause – reduce our reliance on carbon based sources of fuel.


Other excellent blogs on Ocean Acidification:

Australian and New Zealand Ocean Acidification Project

Common synergies


Algal turfs (brown fuzzy stuff) are overgrowing the hard corals at high CO2 concentrations near volcanic vents – a good “natural” experiment. Note also that the seagrass (green, long leaves) are also doing well – a subject for another post.

We frequently hear about “climate change” in the media these days. How could you avoid it? If you do a search of the scientific literature there are thousands of publications a year on the topic. When thinking about the worlds oceans, the most common things that we hear about are ocean warming or ocean acidification (aka. the “evil twin” of warming). Do you notice somthing about this statement? We hear about warming OR acidification. But is this a realistic scenario?

We as scientists commonly break things down into their components and try to understand them one at a time. This is understandable, because the best way to comprehend the functioning of amazingly complex systems is to break them down their component parts and then put them back together again. In this case, however, we are just starting to understand that by breaking things down to individual conditions, either temperature or acidification, we may be missing the most important part of the study. My research group started to realise this in 2009 when we discovered that, when increased in combination, carbon dioxide and nutrients had a massive effect on the growth of “weedy” species of algae which can help to maintain the loss of kelp forests (download the paper here). In hindsight, this result should not be so surprising – both carbon and nitrogen are resources which the algae use to grow. Isn’t hindsight a wonderful thing?

What was surprising is that when carbon dioxide was elevated in the absence of nutrients these algae didn’t respond by grow faster. In fact, they didn’t respond at all to the increased availability of carbon. This means that CO2 and nutrients cause a synergistic response in these algae – where the response to the combined conditions is greater than the sum of responses to the individual conditions (see here for a good review on the topic).

What now worries us is that increasing availability of carbon in the oceans will happen with ocean warming – these are not either/or conditions. Indeed, the first warning shots were fired when we discovered that these same “weedy” turf algae showed the same synergistic growth in response to combined CO2 and warming (see our results published here). We can do something about nutrient pollution (something I will post on in the near future), but CO2 and warming are inherently linked. I think it is time to not talk about warming or acidification but rather to discuss them in tandem.

Report card on Australia’s oceans

I love being a scientist. It can be the most self-indulgent of careers and I feel lucky to live in a society that allows me the freedom to pursue ideas and information. I have the opportunity to explore ideas about how humans interact with our oceans, how we do bad things to them, and most importantly to me, try to figure out how to help them recover. The first step is gathering this information so that people can access it.

While scientists often disagree on things (a very important part of the job), getting a group of scientists together on a problem can truly help to pull together a massive amount of information very rapidly. In this spirit, the “Marine Climate Change Impacts and Adaptation Report Card (Australia)” was released last week. I am lucky enough to have been involved with two of the chapters, observed impacts of Ocean Acidification and observed impacts on marine Macroalgae. Unfortunately, I’d have to say that things aren’t looking good. We are only at the leading edge of some of the changes we are going to see over the next 100 years and some of the observed changes are already bad.

An example that most people wouldn’t know about (because you can’t see it from the surface) is the shift in the distribution of some algae. Algae, aren’t they just the “seaweeds” that we see washed up on the beach? Well, yes, but before they get to the beach they are the foundation of many food webs of the ocean; if they are lost then so are the ecosystems that they support. I must be honest here, when we started this project I didn’t actually expect to find anything to have happened yet, but it has. We have documented substantial southward shifts of entire assemblages of these algae on both the east and west coasts of Australia.Why? The waters of both coasts have warmed rapidly over the past 50 years. In fact, the Leeuwin Current was so strong this year with warming and El Nino that it pushed well into South Australia (see here for a Sea Surface Temperature image from IMOS). Not unheard of, but becoming stronger and more common.

Are we in danger of losing our iconic kelp forests? If so, what will happen to the ecosystems that they support (including 100’s of millions of dollars worth of fisheries)? Only time will tell, but I sincerely hope we can figure out a way to help them…..

The present…..










The future?

Super trawler, Super bad?

Over the past week there has been a lot of media attention thrown at the imminent arrival of a super trawler in Australian waters. It seems that there is strong objection from a lot of the population but objections are far from unanimous. So, what are the issues surrounding super trawlers? Well, it depends on your point of view:
1. Bycatch.

Bycatch, or non-target species caught in the nets, is an issue with trawlers – all trawlers. The size of the nets on super trawlers will mean that there is a large amount of bycatch (e.g. dolphins, turtles, sea birds) regardless of devices designed to limit bycatch being placed in the nets. This is sad and wasteful, but an issue with all trawling activities.

As an aside, I personally don’t believe that the use of the term “gently” with reference to these excluder devices
(“excluder device inside the net guides the animals gently up to an escape hatch on the top panel on the net” – see the article on ABC news for the full quote)

2. Jobs.

If I were the owner of a smaller trawler, I wouldn’t like to be sharing my fishery with this boat. Hundreds of fishermen around the world have been put out of business by big boats and collapsing fisheries……

3. Overfishing.

This is an interesting one. TECHNICALLY, if an effective quota system is in place on this fishery then the addition of this super trawler will not increase the likelihood of over fishing. However, I think this is the main issue in the debate. If you look at global fisheries, the vast majority are either fully or over exploited already. A lot are in an unarrested free-fall. Why? Because we’ve become way too good at catching fish. Our current level of technology means that if we don’t have accurate assessments of fish stocks, and believe me this is a supremely difficult task (so all credit to the people who have to figure it out), then we have the industrial power to over fish a stock before we even know it’s happening. In my mind, this is the real issue with such large boats.

But, this also brings me back to one of the issues I have with the way that society currently looks at problems. If you break something, or there is too little of what you want, don’t change what you’re doing just engineer a better way. With fishing that means bigger, more efficient boats. With climate change, it means geoengineering or carbon mitigation. But, why capture carbon dioxide through a chemical reaction and inject it deep into the ocean rather than switching to non-carbon based sources of fuel? At best you’re buying time to make appropriate changes, at worst you’re creating a false sense of security that will lead to disaster.

Are we risking the same choice with the super trawler?