How Tiny Microbes Rule Our The Ocean
Majestic, ominous, and grand. When these words are placed together for a description, it seems to be for a fierce creature, maybe even a mighty ruler. Rather what I meant to describe with these words was the ocean. Not only is it an endless and jaw dropping masterpiece, it is the home of hundreds of different creatures. The ocean is the perfect, tall, elegant, and divine woman who can handle everything with grace even though she is a busy and loving mother. She acts with confidence, not like she is above others but like she knows to respect herself and does the same for others. She remains collected through her struggles and has a cool charm that instantly attracts the crowd's gaze. Although the show that she put on was stunning, behind the curtain the unseen stage crew works to keep her on her feet. This stage crew is more specifically called microbes.
Microbes can be thought of as tiny living organisms that are too small to be seen without a microscope. The most common types are bacteria, viruses, and archaea. Less well-known groups include protozoa and microscopic algae. These microbes can be found anywhere including soil, air, water, and the human body itself. Most of them are known to be helpful; they produce oxygen, help form soil, and helps us digest food. In contrast, the harmful ones usually make animals and humans sick. For example, the common stomach flu is caused by a microbe, Norovirus.
When the word "marine" is placed in front of microbes, however, it gets a little bit more complicated. Our five major groups turn into bacteria, archaea, phytoplankton, protozoa, and marine fungi, although the focus usually remains on the first three.
Saying marine bacteria are abundant would be an understatement. They are everywhere and anywhere in the ocean. A milliliter of seawater contains hundreds of thousands to over a million bacterial cells, depending on the location.
These bacteria come in four different shapes. When they are round or have a spherical shape they are cocci. They are called spirilla when they have a corkscrew like spiral form. Bacilli are rod-shaped bacteria and vibrios are curved like a comma. The final type are spirochetes, which are known for their flexibility and corkscrew-like body that twists as it moves.
One of marine bacteria's main roles in the ocean is to recycle nutrients by breaking down dead plants, animals, or waste. This allows for nutrients to be released back into the water for other organisms like phytoplankton to use and it cleans up the ocean's natural debris. For example, some of these organisms that are broken down have carbon inside of them so when they are broken down the carbon is released back into the ocean for other living things to use. Similarly, some bacteria change the nitrogen into a form that marine creatures can use. Cyanobacteria, for instance, are known to make their own food using sunlight but during this process they release oxygen. In fact 20-30% of the world's oxygen is made solely by cyanobacteria.
Similarly, marine archaea are single-celled microorganisms. They are comparable to bacteria in size, appearance, and structure. They are also classified as prokaryotes. Much like bacteria they cannot be seen with the naked eye, can be found around the ocean, and are abundant, in certain areas, archaea are more common.
Much like bacteria, archaea come in the two common shapes cocci and bacilli however archaea usually is not found in spiral-like shapes. Some can be irregularly shaped with no real structure. Disc-shaped flat, circular cells, although less common, can also be found.
Much like marine bacteria, archaea swim using their flagella and reproduce through binary fission. There are many different species of marine archaea throughout the ocean which are different in their own ways.
Marine archaea are known for living in extreme environments where few organisms can survive such as hydrothermal vents. Archaea use chemicals to make their own energy so they can live in deep sea ecosystems where sunlight is impossible to find. In fact, scientists used to believe that marine archaea only lived in extreme environments.
Marine phytoplankton are a little different than archaea and bacteria. They are also single-celled microorganisms; however they are more plant-like. Also unlike bacteria and archaea marine phytoplankton are mostly eukaryotes, meaning they are more complex cells that have a nucleus (essentially a brain) and other organelles. Because many different microorganisms fall under the marine phytoplankton category some of them are prokaryotes. In fact, cyanobacteria, which was mentioned before for its contribution of oxygen to the world, is technically also phytoplankton. Thus, some bacteria do fall under the phytoplankton category. Phytoplankton can also be a lot bigger than archaea or bacteria. While they range from 0.2-2 micrometers phytoplankton can go all the way up to 200 micrometers, 100 times bigger than some of the biggest bacteria.
Like other microbes, phytoplankton can be found nearly everywhere in the ocean, although they prefer to stay in the sunlit zone known as the photic zone. This is because phytoplankton uses photosynthesis, like all plants do, to create their energy by using sunlight. Phytoplankton is also extremely abundant. Billions can be found in the world's oceans. They are known for making up the base of most aquatic ecosystems and food chains, as shown below.
There are three main groups of phytoplankton: diatoms, dinoflagellates, and coccolithophores. Diatoms are usually found as a circle or a long rectangle. They have a strong shell around them made of silica which makes them look like they are little discs with detailed patterns in most cases. Diatoms usually depend on the ocean's waves to move them around because they do not have flagella or other structures for swimming, so they rely on ocean currents to move them. Dinoflagellates can be round, elongated, or oval with two whip tails called flagella which help them swim through the water. Coccolithophores are the smallest and they are ball-shaped. They get their name from the calcium carbonate plates that overlap to cover them, called coccoliths. Coccolithophores can also look like miniature decorated spheres. They are different in the way they help the ocean which is explained in the Venn diagram below.
Additionally, phytoplankton also reproduce using binary fission and will also grow rapidly. There are thousands of different species of phytoplankton. Different adaptations in size and shape have made them more complex as well as suitable for aquatic environments.
As mentioned before phytoplankton act as the base of the food web, in other words it is the first link in the chain. They get eaten by zooplankton that then become food for larger animals like fish. Without phytoplankton many marine animals could not survive. Another major role that they have is producing oxygen. Phytoplankton is credited for producing 50% of the world's oxygen. This is done through the process of photosynthesis which also means that it takes in carbon dioxide from the atmosphere around it. By doing this, they keep the ocean healthy and support life within it
When we look into the ocean or think about its beauty we think about coral reefs, colorful fish, and large whales. The image we would conjure would be similar to the one above. But in reality the beauty is in hiding. It lies within the marine microbes who make sure all the algae, whales, and colorful corals have a suitable environment to live in. In the end, the strength of the oceanic system does not come from its largest creatures but from the stage crew, invisible to all, that keep the show going.
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