There are many planets in this Galaxy. To the best of our knowledge, Earth is the only planet in all the Milky Way, better yet - the Universe, on which life exists. Of course, we have been venturing into space for only a little over half a century, and even our best knowledge can be flexible. As yet, there is no real evidence that living things exist on other planets.
Why do living organisms exist on Earth and not on Mars or Venus? Why should Earth, an unstable geologically-active planet that would often (and still does) shift and grind and erode and erupt along with the occasional rumbling of an unpredictable storm or another phenomenon perplexing enough to vex all the meteorologists and geologists around the world, have the honour to be the home of so many lives? Why not?
The Right Balance
Earth has the ideal gravity to hold on and develop an atmosphere that is light enough to hold oxygen, suitable for deflecting most of the lethal rays and thick enough to burn up random meteoroids while still allowing enough heat and energy from the Sun to seep through for necessary life processes like photosynthesis. For over three billion years the rather temperamental Planet Earth has somehow managed to maintain the right temperatures for life to exist, delicately balancing between the incoming rays and the ones Earth had radiated back into space.
How could the same unstable planet keep from disrupting such equilibrium? Scientists found that very answer and quite a lot of other answers when they stumbled upon the (mind-boggling) coccolithophore.
What are Coccolithophores?
Coccolithophores are marine-dwelling phytoplanktons (tiny micro-organisms - they cannot be seen with the naked eye - that live in the mixed (upper) layer of the sea and are eaten by zooplankton and small fish). They can grow in nutrient-poor conditions that other phytoplanktons cannot flourish in. Covering up to 1.4 million square kilometres1 of ocean surface each year, coccolithophores have tremendous effects on both local and global environments.
One of the more conspicuous effects is the long-term/short-term relationship of coccolithophores with carbon dioxide and global warming. The Earth is undergoing global warming, mostly caused by greenhouse gas emissions trapping heat in the atmosphere. But has the world begun to pay the loggers to leave trees alone, passed laws to clean up the oceans, given full consent to the Kyoto Protocol? Alas no, which is why there is so much greenhouse gas such as carbon dioxide and methane.
Our problem: Humans annually release over six billion tons of carbon dioxide by burning fossil fuels and other activities, yet the scientists have found only three billion tons in the atmosphere; one can only wonder what has happened to the other half, for three billion tons of carbon dioxide cannot simply disappear without a trace.
Solution: One coccolithophore is built up of numerous coccoliths, chalky, plate-like formations of calcite. Coccoliths are made up of one part carbon, one part calcium and three parts oxygen; CaCO3. Every time a molecule of coccolith is produced, one less carbon dioxide molecule is floating around as a greenhouse gas. Coccolithophores also consume carbon dioxide by photosynthesis. The majority of the 'vanished' carbon dioxide was sequestered by and converted into coccolithophores.
Can coccolithophores counter global warming? Maybe. Should scientists accelerate the growth of coccolithophores? These phytoplanktons have already removed tons of carbon dioxide by taking out the carbon to create the coccoliths.
Supporters of coccolithophores' population increase should be aware that the same formation of coccoliths that has reduced the amount of carbon in the air also produces carbon dioxide molecules from oxygen and carbon in the oceans. Those molecules will most likely be used by coccolithophores, but some may escape back into the atmosphere.
It is possible that, in the short-term, global warming could cause the upper layers of the ocean to become calmer and more stagnant, which would increase the population of coccolithophores, which in turn would increase the amount of greenhouse gas escaping into the atmosphere. Right now, however, the statistics show a consistent removal of carbon dioxide from the atmosphere (three billion tons a year). Coccolithophores also use up a vast quantity of bicarbonate ions in the ocean.
DMS Cloud Formation Cycle
Another compound that coccolithophores produce is dimethyl sulphide (DMS). Coccolithophores absorb sulphur compounds in the ocean and release DMS when cells die. The gaseous DMS undergoes chemical transformation in air and sea until it becomes a sulphate particle that condensed water vapour uses as a condensation nucleus to form clouds.
Basically, the more coccolithophores there are, the more DMS gets released, and the more clouds are formed. The clouds mean more layers to block the Sun's rays, an increase in precipitation and overall, a cooler Earth.
What is the problem here?
The Sun provides energy on which the plants are dependent. Plants often found in the upper and middle layer of the oceans, where the rays can penetrate, also need the Sun's energy. Coccolithophores are plants (algae). If more clouds meant less sunlight could get through, then photosynthesis would fail to provide energy for everyone. If a living organism cannot get enough energy, it will die off.
Then there would be fewer coccolithophores left as there would not be enough energy for every coccolithophore to survive. Less DMS would be released, less clouds made for want of condensation nuclei, the sun would shine once more and lo, behold! In the oceans, the coccolithophores dwell once more in multitude... This DMS cloud formation cycle is repeated over and over again. This is how coccolithophores have helped Earth maintain stability at a generally tolerable temperature for millions of years.
Coccolithophores have extremely interesting effects on their own environments as well. A peculiar effect caused by the coccolithophores is that they increase albedo, or the amount of sunlight that an object reflects, and they change of colours of the oceans that are their habitats. Coccolithophores can 'bloom'2 and an area of ocean thus affected can reflect three times as much sunlight back into space. This light scattering turns the water a milky turquoise colour and is also the origin of nicknames such as 'fairy glow' and 'white water'. The waters underneath coccolithophores will become darker and may block the light necessary for the photosynthesis process of other organisms to take place. This massive 'light-scattering' has made it much easier for the climatologists to use satellites to detect and keep track of coccolithophore populations more accurately.
Earth is an intricate interchanging system interwoven with the acts and vital contributions of each diverse living (micro-)organism's functions in life. By simply existing and surviving, the coccolithophores have played an essential role in the lives of everyone on Earth (where else?). For what coccolithophores lack in size, they more than make up for in volume and the vast amount of atmospheric carbon dioxide that they consume annually, as well as their role in producing DMS. One coccolithophore species, Emiliania huxleyi or E. huxleyi, alone can cover more than 100,000 square kilometers3 of ocean surface and can produce tens of thousands of metric tons of CaCO3.
There are no small parts, only small actors.
- Movie maker Alfred Hitchcock
Never let it be said that size is relevant in importance. Coccolithophores are the prime example of this maxim. Talk about the amazing impact these small actors have had on us!
1 1 kilometre = 0.62 miles: for anyone interested in conversion, divide 1.4 million by the square root of 0.62... we'll get back to you on this.
2 Bloom - a coloured area on the surface of oceans, lakes or rivers caused by a population explosion in the algae living there.
3 The same area as England.