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Discover: Importance of Marine Microbes
“Without microbes we couldn’t eat or breathe. Without us, they probably would be just fine.”
(www.microbe.world.org/microbes / on What is a microbe page)
Would you believe marine microbes help you and I breathe easier? Would you also believe that the
same marine microbes have a hand in maintaining our planet’s stable climate that allows life to exist?
And would you also believe that microbes account for more than 90% of ocean biomass and make up a
hidden majority of the life that inhabits the sea. Well in each case, if you don’t believe it, you’d better
give it a second thought, because microbes are really that important! Below are just three reasons why
marine microbes are important to life on Earth.
http://www.caml.aq/microbes/index.html
http://www.marine-genomics-europe.org/upload/phytoplankton_cycle_copie.jpg
1. Photosynthesis - Plant-like marine microbes
(mostly phytoplankton and cyanobacteria) are
estimated to provide more than 70% of the
oxygen we need to breathe. The oceans have
been called “earth’s last great forest” in
reference to the huge influence these organisms
have in the producing oxygen. Without them,
you probably would not be reading this today.
THANK YOU microbes!
2. Respiration - All marine organisms including
microbes give off carbon dioxide in the process
of releasing energy (yes even plant-like
organisms). There is a massive abundance of
microbes in the world’s ocean which tend to
give off large amounts of carbon dioxide. This
carbon dioxide is then absorbed and used by phytoplankton and other autotrophic organisms to
perform photosynthesis. Of course these organisms then release oxygen, which we and other
organisms depend on to breathe. Once again, THANK YOU microbes!
3. Nutrient Recycling -The really neat thing about marine microbes, specifically bacteria, is the
unique role they play in recycling nutrients and transferring energy within the marine food web.
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Simply put, bacteria are decomposers. They breakdown dead animals, plant matter, and organic wastes
created by all living things. If they didn’t we would be swimming and fishing in an ocean that would
quickly amount to a pile of dead plant and animal remains. As you can imagine, this would not be a
pretty sight!
But if everything else is producing their own food or eating other organisms for energy, how do
microscopic bacteria get their food and energy? Most are unable to photosynthesize like plants, they
have no mouth to ingest food, and there is no living organism smaller than them to prey upon. Instead
bacteria are able to consume some of the material they are decomposing. This material available only
to bacteria as food is called dissolved organic matter (D.O.M.) and it originates from anything that was
once living and always contains carbon molecules. Examples include the dissolved remains of dead
organisms, excreted wastes from zooplankton (and larger organisms!), the gelatin-like cytoplasm of
single celled critters, sea slug secretions, and even blood…just to name a few! In truth, the ocean can
be thought of as a big tub of extremely diluted jelly made up of dissolved organic matter.
Put another way: You can think of D.O.M. as a slice of pizza (or any
other food) that has been put into a blender with some water and made
into a pizza soup. It’s still pizza and has nutrients and energy, but
instead of needing a mouth to eat it, now all you need is a method of
absorbing it into your body. There are all kinds of D.O.M. floating
around the ocean and bacteria take advantage by using it as a source of
nutrition and energy.
Yuck maybe, but that “D.O.M. stuff” is really important. Carbon
molecules are the essential building blocks of all life and Earth came
with only a limited supply. Unfortunately, once carbon is converted
into D.O.M. it can no longer be directly ingested by larger marine
organisms and used as a source of energy.
So, what happens?
As just mentioned, bacteria consume D.O.M. Larger microscopic
organisms called protozoans, such as flagellates and ciliates, then
consume the bacteria. The “unusable” carbon that had been floating aimlessly in the ocean depths is
now recycled back into the marine ecosystem and the energy it contains is transferred up the traditional
marine food chain to be used by larger organisms. Without the bacteria at the base, this energy would
never make it back to the top. This cycling of matter and energy within the microscopic realm is
referred to by scientists as the “microbial loop.”
Protozoan
Bacteria
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Quick Quiz:
1. All of the following are reasons why marine microbes are important to life on Earth EXCEPT:
a. bacteria are decomposers and play a critical role in recycling nutrients
b. plant-like marine microbes play provide more than 70% of the oxygen humans need to
breathe.
c. Marine microbes do not play an important part in the respiration process
d. both a and c
2. Bacteria are can consume:
a. dissolved organic matter and always contains carbon molecules
b. whole phytoplankton cells that always contain carbon molecules
c. dissolved organic matter and never contains carbon molecules
d. whole phytoplankton cells that never contain carbon molecules
References: Marine Microbial Ecology Southern Australian Government - Division of Environment
and Heritage - Australian Antarctic Division: http://www.aad.gov.au/
Cycling through the Food Web: http://www.bigelow.org/bacteria/
Microbe World:http://www.microbeworld.org/microbes/bacteria/
Microbial Food Webs: http://oceanworld.tamu.edu/resources/oceanography-book/microbialweb.htm