Spirals in Time: The Secret Life and Curious Afterlife of Seashells (39 page)

‘It’s like a big rain shower over a desert,’ is the way Ulf describes the upwelling event to me. He is still wide awake and brimming with enthusiasm when we sit down to chat about the project. There is one thing in particular I want to ask him about, something that has been bothering me for a while: the passing of time.

Why time matters

Most ocean acidification studies take place over the course of hours and days and a few, like KOSMOS, keep going for months. But out in the real world, there is a hundred years to go before ocean pH is expected to reach extremely low levels. In that time, will marine life be able to adapt to the creeping changes in the world around it?

This is a major limitation of most ocean acidification studies; critics point out that they take place too fast, and don’t continue for long enough, to truly mimic acidification in the oceans. A few longer-term studies hint that there is scope for adaptation, but perhaps only up to a point. Ulf’s research group has bred phytoplankton called coccolithophores for 1,800 generations in high carbon dioxide conditions. These microscopic algae live inside clusters of calcium carbonate discs – collectively called the coccosphere – making them likely victims of acidification. However, over
time, the laboratory population became more robust to falling carbonate saturation and lower pH.

The experiment acted as a form of artificial selection. The high carbon dioxide treatment slowed the growth rate of some coccolithophores, probably because they needed more energy to keep building their carbonate skeletons. Meanwhile some of them were more robust and were able to maintain their growth rates, perhaps even growing faster. These individuals were the ones that reproduced more rapidly, passing on more of their genes to the next generation. Slowly, in laboratory conditions, the acidified coccolithophores became adapted to their shifting water chemistry.

It remains unknown exactly how the coccolithophores’ physiology changed; it’s possible that as generations went by, they became more adept at ramping up metabolic rates and pumping ions around to maintain pH balance. Or, there may be some other as-yet unidentified mechanism that allows them to survive.

Could other calcifiers adapt to acidifying waters like coccolithophores? To repeat the experiments on anything that lives longer than these microbes would take an insanely long time. Coccolithophores have a generation time of a single day. It took five years to study them for 1,800 generations. For organisms like sea butterflies that have generations lasting a year, these experiments become quite unthinkable. Plus, it’s well known that organisms with short generation times evolve quickly, compared to species that take longer to mature and reproduce (this is because the genomes of short-lived species are copied more frequently and errors quickly build up in their DNA, leading to more genetic variation that natural selection will act on). Coccolithophores are also highly abundant, with up to 10 million of them in a litre of seawater. It means that coccolithophores are inherently more adaptable to environmental changes than larger, rarer species like sea butterflies. And like Steeve Comeau’s naked sea butterflies, the big unknown is
whether carbon-resistant coccolithophores would survive out in the oceans, where there are masses of other species all competing for resources and space.

Even those organisms that can change their ways and adapt to a high carbon dioxide world may eventually still lose out. As the oceans continue to acidify, the cost of concentrating carbonate ions and building skeletons and shells will keep on steadily rising until calcifiers can simply no longer afford to make their homes.

‘There are certain limits you can’t pass,’ Ulf tells me.

The century of acidifying seas that lies ahead will be unavoidably long and slow compared to the short-term studies aiming to forecast the future (after all, the only way to really know how the oceans are going to respond is to sit back and watch what happens in real time, but that’s hardly the point of studies like this). However, the rate at which ocean acidification is now taking place is a mere beat of a sea butterfly’s wings compared to the millennia that rolled by in previous climate change events, the ones that came and went before modern humans showed up. Sceptics point to these past events, to times when carbon dioxide levels were naturally high without humanity’s input.
And look – look at all those things that were alive back then and are still here now
. There are still corals and plankton and all those molluscs with shells. They didn’t melt away before, so why should we believe that will happen this time?

Things are different now. Given enough time, and a slow enough pace of carbon enrichment, the oceans themselves respond to ocean acidification and lessen its effects. Deep down on the sea floor there are vast deposits of calcium carbonate sediments, made from the fossilised remains of calcifying creatures – mostly coccolithophores and foraminifera – that lived and died over millions of years. In the past, carbon dioxide levels have risen in the atmosphere as is happening now, but from other sources besides human activities. The pH of shallow seas fell and, over the course of
many centuries, those surface waters sank down, until they reached the deep carbonate sediments, causing them to dissolve and release carbonate ions. It meant that levels of carbon dioxide in the atmosphere were decoupled from the saturation of carbonate ions in the seas; while atmospheric carbon dioxide increased, it didn’t drag down carbonate saturation with it. In essence, the oceans had their own colossal mechanism that buffered against acidification, which explains why many creatures with chalky skeletons were able to survive previous climate change events. In the past, calcifiers were protected from acidification by their ancestors – calcifiers of earlier eons – whose remains accumulated on the seabed. But now that link has been broken. The problem is, the oceans’ inbuilt balancing mechanism takes 1,000 years or more to work, because that’s how long it takes shallow waters to spread through the deep ocean. This time around, we don’t have 1,000 years to wait.

Anthropogenic climate change is taking place much faster than anything the planet has experienced before, and the oceans can no longer keep pace with carbon emissions. The rate of uptake of carbon dioxide into the oceans far outstrips their ability to buffer against falling pH. Now, carbon dioxide levels and carbonate saturation are locked in relentless decline; side by side they drop together. The oceans today are slaves to the atmosphere.

A major talking point for climate change – and a target for sceptics – is the issue of how much experts agree on the facts. Increasingly, scientists worldwide are standing up and making it abundantly clear that they do agree, by and large, on the causes of climate change and the global troubles that could lie ahead. On a similar note, do experts agree that ocean acidification is happening, and that it’s a problem for the seas? A 2012 survey of experts suggests that consensus is strong, at least when it comes to the bigger issues.

Jean-Pierre Gattuso
from the Laboratoire d’Océanographie in Villefranche, France, led a survey asking 53 ocean acidification experts how much they agreed, or disagreed, with a list of statements. Almost all the experts agreed – without question – that ocean acidification is currently in progress, that it’s measurable, and that it is mainly caused by anthropogenic carbon dioxide emissions ending up in the oceans (many pointed out that in coastal waters other pollutants, such as excess nutrients, can also affect pH).

As is the scientist’s prerogative, many respondents picked apart the questions being asked, pointing out problems with the wording: ‘What do you mean by “most”?’, ‘What does “adversely affect calcification” mean?’

In many cases, they emphasised the lack of certainty, the lack of long-term studies and the variable responses of different organisms. Without more data, it’s difficult to be sure how food webs and fisheries will fare in a more acidic world. However, experts did agree that calcifiers, with their chalky skeletons and shells, are the marine species most likely to lose out.

Experts are also largely agreed that the ocean-atmosphere system has momentum. Even if carbon emissions were eradicated tomorrow, the oceans would continue to acidify for centuries to come. As one scientist put it, ‘This is physical chemistry … I don’t think there is any other possibility.’ Does this mean that ocean acidification studies, like the KOSMOS mesocosms, are simply casting predictions about a global experiment that will run on regardless of their findings, and regardless of how humans behave in the next few decades? If ocean acidification really is inevitable and unstoppable, maybe it doesn’t help to wrap our minds around the reality of how bad it will get. Perhaps we are better off not knowing.

I don’t think so. There’s no avoiding the uncomfortable truth that the only way to limit ocean acidification and the other problems of climate change – to stop the situation
from becoming utterly disastrous – is to make drastic cuts to escalating carbon emissions, and to do it now. Decision-makers need to see these predictions, based on the best available science, of what a future world will look like so they can understand what it is that we’re losing, and why action must be taken. The same goes for the rest of us. For most people, most of the time, ocean life is out of sight and out of mind, but there are plenty of good reasons why we should all sit up and take notice, and start caring about these vital, hidden worlds.

I felt a sense of great privilege peering at those sea butterflies and the other planktonic creatures as they whizzed around their glass-walled world, oblivious of me watching them. It was as if I had been let in on some of the oceans’ greatest secrets, but who knows how much longer they will all be there? Of those spinning specks of life, some will be winners and others losers in the lottery of warmer, stormier and corrosive seas. And the really frightening thing is that the problems of the oceans don’t stop at carbon. We are fishing deeper and further from shore than ever before, plundering wild species and treading paths of destruction through fragile ocean habitats. Dead zones are proliferating; garbage is piling up, transforming the open seas into toxic, plastic-flecked soup. All these troubles and many more combine, acting in concert to worsen each other. It’s easy to feel overwhelmed, and utterly helpless in the face of relentless bad news.

But the problems are not all far away, nor are they out of our hands. It matters what each one of us decides to do, what we choose to eat, what we buy and what we throw away. We have the power to lighten our impact on the blue parts of our planet. Curbing as many individual problems as possible will give the oceans a chance to rest, to recover and restore themselves, and resist the impacts of climate change. If we act now, there’s hope that in the years ahead there will
still be a wealth of wonders in the oceans; there will be food for millions of people, from nutritious bowls of clams to the indulgent treat of flinty, raw oysters; sea snails will sneak up on sleeping fish and scientists will probe their spit for new inspirations; each night, nautiluses will rise from the inky depths, as they have done for hundreds of millions of years; tiny snails will fly around the open sea, spin webs to catch their food and be chased by other flying snails that don’t have shells, and octopuses that do. And there will still be beautiful shells washing up on beaches, where people will find them and wonder where they came from, and how they were made.

Epilogue

I
n the summer of 2014, Philippe Bouchet led a team of mollusc-hunters to Nago, an island off the coast of Papua New Guinea, which lies in a coral-dotted lagoon stretching between the Bismarck Sea and the Pacific Ocean. This spot lies towards the eastern end of the Coral Triangle, the place where there are more marine species than anywhere else on the planet. Throughout years of field trips – in Vanuatu, Madagascar, the Philippines and elsewhere – Bouchet and colleagues from dozens of countries have been honing their collecting techniques. Divers venture out both day and night, so as not to miss the nocturnal species; they drop sampling devices down to varying depths where, like layers of a forest canopy, different assemblies of animals are found; they search between the tides; they even check among the spines of sea urchins and the tube feet of starfish for parasitic snails that suck the echinoderms’ bodily fluids. The teams have also begun taking snippets of tissue to preserve the animals’ DNA so species can be identified from their genetic fingerprint.