Ocean Plankton Reducing Greenhouse Gases By Using More Carbon Dioxide

ScienceDaily (Nov. 18, 2007) — Microscopically tiny marine organisms known as plankton increase their carbon uptake in response to increased concentrations of dissolved CO₂ and thereby contribute to a dampening of the greenhouse effect on a global scale. An international group of scientists led by the Leibniz Institute of Marine Sciences in Kiel, Germany documented this biological mechanism in a natural plankton community for the first time.

In simulations of the future ocean, they measured an increased CO₂ uptake of up to 39%. The unexpected positive effect for the global climate system harbours at the same time considerable risks for the oceans and their ecosystems.

The study points to three major areas of concern: increased CO₂ uptake by plankton will accelerate the rate of ocean acidification in deeper layers, lead to a decrease in oxygen concentrations in the deeper ocean, and will negatively influence the nutritional quality of plankton. The latter development can have consequences for entire food webs in the ocean.

The world oceans are by far the largest sink of anthropogenic CO₂ on our planet. Until now, they have swallowed almost half of the CO₂ emitted through the burning of fossil fuels. However, can the oceans continue to alleviate the steady rise in atmospheric CO₂ in the future? Current models for the development of the global climate system do not incorporate the reaction of marine organisms nor the processes that they influence.

Professor Ulf Riebesell, marine biologist at IFM-GEOMAR in Kiel and the first author of the study, gives insight into the motivation for the research: “We need to learn a lot more about the biology of the oceans, because the organisms play a decisive role in the carbon cycle. How do they affect the chemical balance and what are their responses to the enormous environmental changes we are currently experiencing?” The Nature publication provides new insights into these effects and their dimension.

To investigate the biological processes and their potential changes with time, the scientists made use of an unusual experimental set up in the Raunefjord in Norway. Here, a series of nine mesocosms, enclosures manufactured from a specialized synthetic material and measuring 10 meters in depth, were used to isolate 27 cubic meters of natural fjord water. In the experimental design, Ulf Riebesell and his team maintained three enclosures at current CO₂ conditions as a control, while they infused CO₂ in the remaining mesocosms to simulate predicted concentrations for the year 2100 and the year 2150.

The critters in the mesocosms responded quickly to the extra serving of CO₂. The higher the concentration of dissolved carbon dioxide, the faster the microalgae incorporated the greenhouse gas via photosynthesis. Can CO₂ act as a fertilizer in the ocean? The scientists measured an increased uptake of up to 39% compared to current rates.

Ulf Riebesell describes the reaction of his team: “We expected the organisms to show distinct reactions to changing CO₂ conditions. What really surprised us, however, was the dimension of this effect. Basically, we can now say that the biology in the oceans is significantly affecting the global climate system.” In the final step of the experiment, the scientists wanted to find out what happens with the rapidly proliferating biomass. Again the experiments in the Raunefjord provided insights: the extra CO₂ bound in organic matter sank to depth after the peak of the algal bloom.

The CO₂ fertilization of marine plankton can have a positive effect on climate change in the future. The greenhouse gas consumed by plankton and removed from the surface ocean when the dying cells sink to depth makes way for the uptake of more CO₂. In a way, the tiny organisms act as a biological conveyer belt for the transport of carbon dioxide out of the surface and into the deep ocean.

What appears to be a blessing for the atmospheric greenhouse effect may prove to be a curse for deep ocean ecosystems. Decomposition of the increased biomass will consume more oxygen, a major problem for marine animals that occupy deep habitats. Another consequence of the biological conveyer belt is the accelerated rate of ocean acidification in the deep ocean due to more rapid transport of CO₂ to depth. The authors also expect direct affects on marine organisms based on previous observations. Planktonic crustaceans that were fed with CO₂-enriched microalgae displayed slower growth rates and were less proliferous.

Ulf Riebesell remarks on the consequences of the study: "Our results probably represent only the tip of the iceberg. I am certain that scientists will discover further biological feedback mechanisms in the near future. It is essential not only to identify and to understand these mechanisms, but also to quantify their effect on the global climate system, now and in the future. “

The experiments in Bergen were conducted in the framework of the research program CARBOOCEAN, funded by the European Union.

 

READING 2

Global Warming

Global warming is one of the few scientific theories which makes us examine the whole basis of modern society. It is a theory that has politicians arguing, sets nations against each other, queries individual choices of lifestyle and ultimately asks the questions about humanity’s relationship with the rest of the planet. There is very little doubt that global warming will change our climate in the next century; our best estimates suggest an average temperature increase of 1.4–5.8°C, a sea-level rise in the order of a metre, significant changes in weather patterns, and more extreme climate events. This is not, however, the end of the world, as envisaged by many environmentalists in the late 1980s and early 1990s, but does produce some major challenges for our global society, the most important of which are the moral dilemmas that global warming has precipitated. First, how do we ensure that the Third World develops as rapidly as possible, while preventing a massive explosion in production of carbon dioxide and other greenhouse gases? Second, is the question of whether the money we plan to spend on stabilizing global warming, $8 trillion or 2% of the World’s GDP, to protect future generations is better spent on alleviating current global human suffering? Ultimately, 2% of the World’s GDP is a very small cost if we can ensure that the world economy continues to grow by 2–3% per year over the next century as predicted. So ultimately global warming is an issue of morals and global economics. So what are the solutions to global warming? As we have seen, it is unlikely that global politics will solve global warming. Technofixes are dangerous or cause problems as bad as the ones they are aimed at fixing. Even the idea of using energy more efficiently seems rather inadequate when there are another five and half billion people in the world aspiring to have the energy use enjoyed by the Western world. So the ultimate solution is for humanity to develop cheap and clean energy production, as all economic development is based on ever-increasing energy usage. Though great strides forward have been made in alternative energies, it seems unlikely that these will produce energy on the scale we require in the next few decades. As I am a great believer in humanity’s adaptability, I am sure these will be available before the end of the century. But a considerable increase in investment is required if we are to convert to renewable energy by the end of the century; for example, current US investment in renewable energy is just $200 million per year. Even if renewable energy technology does become available, there is no guarantee that it would be made affordable to all nations, since we live in a world where even life-saving drugs are costed to achieve maximum profit. Nor is there any guarantee that if we had unlimited free energy it would prevent us from continuing to abuse the planet. Paul Ehrlich at Stanford University, commenting on the possibility of unlimited clean energy from cold fusion, suggested it would be ‘like giving a machine gun to an idiot child’. We cannot pin all our hopes on clean energy technology, nor our ability to use it wisely, so we must prepare for the worst and adapt. If implemented now, a lot of the costs and damage that could be caused by changing climate can be mitigated. This requires nations and regions to plan for the next 50 years, something that most societies are unable to do because of the very short-term nature of politics. So global warming challenges the very way we organize our society. Not only does it challenge the concept of the nation-state versus global responsibility, but the short-term vision of our political leaders. To answer the question of what we can do about global warming, we must change some of the basic rules of our society to allow us to adopt a much more global and long-term approach. I leave you with thoughts of redesigning our global community with the excellent words of Professor Wally Broecker of Columbia University (USA): ‘Climate is an ill-tempered beast, and we are poking it with sticks.’

 

READING 3