As more acidic seas spread across the globe, conditions for survival start to change. That could close vast volumes of ocean for vital forms of life.
By the close of the century, parts of the Southern Ocean could become impoverished as more acidic seas displace abundant marine food resources. Tiny sea snails that form the basis of the food supply for one of the world’s richest ecosystems could disappear because the depth at which they can form their shells will have shifted.
Right now, in Antarctic waters, creatures known as pteropods can exploit the calcium carbonate dissolved in the oceans down to a depth of 1000 metres to grow their shells.
But as atmospheric carbon dioxide levels soar, as a consequence of profligate use of fossil fuels by humankind, the chemistry of the oceans will shift towards the acidic.
“A pocket of corrosive water will sit just below the surface, making life difficult for these communities of primarily surface-dwelling organisms”
Right now, pteropods flourish in the top 300 metres of the ocean. By 2100, the survival zone for the pteropods will end at a depth of 83 metres.
And, scientists warn in the journal Nature Climate Change, this could “change food web dynamics and have cascading effects on global ocean ecosystems.” In other words, the larger fish and marine mammals that feed on the smaller creatures that in turn depend on a basic diet of pteropods will have nothing to eat.
And that can only be bad news for global fisheries.
All shelled marine creatures – the tiny coccolithophores that die and leave their shells as chalk, the clams and molluscs, the foraminifera that float on the surface or coat the rocks and the seafloor, and the corals that are the basis for rich tropical ecosystems, all depend on the right levels of calcite and aragonite to form their exoskeletons.
The oceans are the biggest living space on the planet: the waves cover 70% of all living space and the depth of the deepest trenches is far greater than the highest terrestrial mountain ranges.
Origin of life
The oceans are the crucible in which life first emerged, and the oceans ultimately provided the sediments from which humankind has built its cities.
US and Norwegian scientists chose one species with precise needs in one reach of ocean as an indicator or what climate change driven by ever greater levels of the greenhouse gas carbon dioxide could do to an ocean ecosystem.
They found that what they called the “aragonite saturation horizon” became dramatically shallower as the seas became more acidic.
“These calcifying organisms will struggle to build and maintain their shells as acidification proceeds,” said Nicole Lovenduski, of the University of Colorado at Boulder, one of the researchers.
“In the future, a pocket of corrosive water will sit just below the surface, making life difficult for these communities of primarily surface-dwelling organisms.”
As the world warms, acidification of the oceans becomes inevitable. Researchers have repeatedly warned that such change can only diminish ocean life, harm the coral reefs and kelp forests that shelter the rich biodiversity of sea creatures, change the behaviour of fish and some kinds of shrimp and threaten the shellfish harvest.
But for the first time, scientists have been able to model the impact of atmospheric change on the ocean chemistry in one zone at precise depths. The message is that right now, the pteropods have plenty of sea space for survival. But the aragonite saturation horizon may have already begun to shift in some places: perhaps as early as 2006, or as late as 2038. Once change begins, it will continue.
“If emissions were curbed tomorrow, this suddenly shallow horizon would still appear, even if possibly delayed,” said Dr Lovenduski. “And that, inevitably, along with lack of time for organisms to adapt, is most concerning.” – Climate News Network
About the Author
Tim Radford is a freelance journalist. He worked for The Guardian for 32 years, becoming (among other things) letters editor, arts editor, literary editor and science editor. He won the Association of British Science Writers award for science writer of the year four times. He served on the UK committee for the International Decade for Natural Disaster Reduction. He has lectured about science and the media in dozens of British and foreign cities.
Book by this Author:
Science that Changed the World: The untold story of the other 1960s revolution
by Tim Radford.
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Earle takes us along on journeys to places of unimaginable beauty and unutterable destruction. She conjures up the exhilaration of swimming with humpback whales off the coast of Maui; she makes us comprehend the true environmental tragedy of the massive oil spills in Prince William Sound and the Persian Gulf; and she leads us out into Australia's Great Barrier Reef, the epitome of ocean wilderness but also the final resting place for tons of waste that drift in from thousands of miles away. This brilliant, thought-provoking, superbly readable book will inspire a new reverence for the majesty of the world's oceans even as it opens our eyes to the intricate interdependence of all life-forms.
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Ocean's plan includes 31 simple and affordable step-by-step actions that give you a road map to healthy, ethical, and sustainable food. He breaks it down into four parts:
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These are complex, challenging, and critically important themes. How the human relationship to the oceans evolves in coming decades may be one of the most important connections in understanding our personal and social well-being. Yet, our understanding of this relationship is far too limited.
This remarkable volume brings experts from diverse disciplines and builds a workable understanding of breadth and depth of the processes – both social and environmental – that will help us to limit future costs and enhance the benefits of sustainable marine systems. In particular, the authors have developed a shared view that the global coastal environment is under threat through intensified natural resource utilization, as well as changes to global climate and other environmental systems. All these changes contribute individually, but more importantly cumulatively, to higher risks for public health and to the global burden of disease.
This pioneering book will be of value to advanced undergraduate and postgraduate students taking courses in public health, environmental, economic, and policy fields. Additionally, the treatment of these complex systems is of essential value to the policy community responsible for these questions and to the broader audience for whom these issues are more directly connected to their own health and well-being.
"The seas across this planet and their effects on human society and its destiny are a fascinating subject for analysis and insights derived from intellectual inquiry. This diverse and complex subject necessarily requires a blending of knowledge from different disciplines, which the authors of this volume have achieved with remarkable success."
"The following pages in this volume are written in a lucid and very readable style, and provide a wealth of knowledge and insightful analysis, which is a rare amalgam of multi-disciplinary perspectives and unique lines of intellectual inquiry. It is valuable to get a volume such as this, which appeals as much to a non-specialist reader as it does to those who are specialists in the diverse but interconnected subjects covered in this volume."
(From the "Foreword" written by, R K Pachauri, Director General, TERI and Chairman, IPCC)