Bacteria have been on planet earth for a very long time, 3.5 million years to be exact. They live throughout the ocean and have a fascinating array of nutrition modes and morphologies. Some bacteria are aerobic, others are anaerobic. There are bacteria that are able to photosynthesise and some are even able to create light. The bacteria that are able to photosynthesis, known as cyanobacteria, were responsible for the great oxidation event that change the course of life on Earth. If this vast array of bacteria and the effects they’ve already had on earth aren’t enough to make you think they are fascinating then the sheer number of them might be. There is an unimaginable amount of bacteria in the ocean, it has been shown in some studies that for a millilitre of sea water there is an average of two million bacteria! This means that the bacteria population in just 6 litres of water is larger than the human population of earth. If you take these numbers and scale them up, then you learn that the weight of all the bacteria in the ocean weight as much as 5o million blue whales!

What makes bacteria important in the ocean?

By far the largest impact that bacteria have is their ability to recycle nutrients. When organisms die in the ocean they break the dead organism down. By this breaking down of organic matter, they release the nutrients that were previously held in the tissue of the dead organism. This bacterial breakdown is an essential part of the nutrient cycles in the world’s oceans. The nutrients that are put back into the water column by bacteria are used up by other organisms such as phytoplankton and these nutrients are a key part in enabling them to photosynthesise effectively.

How bacteria recycle nutrients and make them available for use by other organisms. Original Source:
How bacteria recycle nutrients and make them available for use by other organisms. Original Source:

Bacteria are vital components of the nitrogen cycle. Although nitrogen makes up most the atmosphere on earth it is unreactive so cannot be incorporated into biological tissue easily, this is where bacteria come in. symbiotic bacteria called diazotrophs fix atmospheric nitrogen with hydrogen using an enzyme called nitrogenase to produce ammonia. The ammonia can then be used to create other biological compounds.  This is obviously a very important process and without it the nitrogen cycle would break down and life wouldn’t be the same on earth.

The cyanobacteria also have a substantial impact on the earth. Half of the world’s atmospheric oxygen comes from the ocean and cyanobacteria are responsible for half of all the oxygen transferred from the ocean to the atmosphere.

Cyanobacteria taking up water and carbon dioxide and releasing oxygen from photosynthesis. original source: How bacteria recycle nutrients and make them available for use by other organisms. Original Source:

What makes bacteria extreme?

If the sheer quantity of bacteria alone or the massive effect the have on global nutrient cycles isn’t enough to make you think they are extreme, then consider all the different places that they live. Bacteria can be found right the way through the ocean, from the surface waters right down to ocean floor sediments. They can survive in cold polar seas and close to hydrothermal vents where they are vital to the ecosystem. The bacteria at hydrothermal vents are symbiotic organisms with other organisms, they are able to get energy from the oxidation of sulphur that comes out of the hydrothermal vents. Nearly all biological chemical reactions can be conducted by bacteria, they are like the swiss army knife of organisms, able to lend their hand to any situation.


Dangers to humans

Humans have been putting sewage into the ocean for as long as anybody can remember. The idea was that due to the vast size of the world’s ocean the sewage was quickly and effectively dispersed into safe concentrations. Due to the rapid expansion of the human population, the dumping of untreated sewage into the sea can have a major effect. Not only does the sewage effect marine coastal ecosystems by introducing more nutrients into the water, pathogens that are normally only found in the digestion systems of humans are released into the sea.  Escherichia coli bacteria have been found in coastal waters near sewage outlets, these bacteria have been known to cause organ damage which in some people can lead to serious illness.

Cases of severe cholera have been noted in Bangladesh and parts of south America. One of the causes of this is thought to be the release of untreated sewage containing the bacteria responsible for the disease, Vibrio cholerae. The release of the bacteria and El Nino events significantly increases the chance of outbreaks and the bacteria is able to reproduce very quickly in the coastal waters.

Harmful bacteria can also be present in high numbers in the ballast water of ships. When ships come into dock they release their ballast water. This releases bacteria that could have potentially come from the other side of the world into a new environment. These bacteria can then be further distributed by ocean currents that can potentially disperse them over a large area of the coast. Once these new bacteria have been released into an environment then can have serious effects on coastal populations of humans that live in the area.

The release of untreated sewage into coastal waters and the harmful bacteria it contains has led to many coastal areas being unsafe for humans. Although some species of bacteria have a negative effect on human’s life on earth as we know it today wouldn’t be possible. Without the great oxidation event or them tirelessly recycling nutrients in the world’s ocean then you or I wouldn’t be alive today.


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