The Phosphorus (FOS-FOR-IS) Cycle
Our next scientifically magical voyage takes us to the world of phosphorus and the way it cycles through the biotic and abiotic stages here on earth. The phosphorus cycle is a bit different from the water, carbon and nitrogen cycles in that it doesn’t involve the atmosphere. At all. There was no atmosphere used in the production of this element. This adds a new layer of mystery to our tale; what the phosphorus is this stuff and how can I get some?
Due to it’s chemical properties (we won’t be exploring these… yet) phosphorus is usually only found on earth as a solid. While there is some amount of phosphorus found in both soil and water, the majority of it is trapped in rocks. So how does nature get to these invaluable phosphorus pockets?
If you look at your coloring paper you will see the letter A is close to some gusting winds and a violent rainstorm. These physical forces contribute to weathering and erosion causing small deposits of phosphorus to be broken down and washed into the soil (C).
Once the soil has phosphorus, our producer friends can grow (D)! Does that mean that plants cannot grow without phosphorus? Yes! So what are the plants using this phosphorus for?
Phosphorus rock.
Phosphorus And You: An In Depth Look at Phosphorus and it’s Purpose Towards Living Things
Phosphorus is needed by producers to make flowers. Without flowers, producers would not be able to reproduce and would become a thing of the past.
Also, all living things need phosphorus to survive. Everything that is living has DNA and in order to make DNA, organisms need phosphorus. Additionally, remember that funny thing that living things use for energy called ATP? Adenosine tri-phosphate? Guess what the phosphates are made of? Phosphorus. So without phosphorus, these organisms will have no energy. Not like, “boohoo I played video games all night and now I am really tired.” It is more like “boohoo I have no energy and now I am dead.” Yes, without phosphorus you and I would not be here. Pretty important huh?
Another important use of phosphorus is that it makes up part of the cell membrane. The cell membranes of all cells and the inside parts called organelles are made up of a phospholipid bi-layer. Phospholipids are fats with a phosphorus atom in them.
Note the P group, in the thing we call ATP, is made of Phosphorus. This is the single unit cells use for energy.
Snap Back to Reality, Whoa There Goes Gravity
Now that we know these plants have phosphorus, let’s look at how the phosphorus passes between organisms. If you look at the coloring picture you will see some fancy zoom technology on the leaves of the plants. Since the leaves have ATP and have DNA, anything that eats the leaves will gain some phosphorus as well.
On your coloring picture you will see a caterpillar munching on the leaves. As it consumes the leaves, it gains phosphorus (E).
We now have a caterpillar chock full of this fancy element. When an organism eats this, let’s say something like a bird, it will now gain the phosphorus from it’s food (F). And so on, and so forth. You can expect phosphorus to continue to flow between consumers all the way to the top of the food chain.
The Circle of Phosphorus
However, all living things have to die at some point. When the organism dies what happens to all of that valuable phosphorus? Well, it’s not lost forever. When the organism dies it will be broken down by decomposers, which are organisms that gain energy by breaking down dead or dying organisms. If you check out the graphic reality of the coloring page, you will see that at letter G we have a dead bird. As fungus, bacteria, worms and bugs begin to digest the corpse, they will gain some of the phosphorus for their own use. What isn’t used is returned to the soil which can give rise to new life (H). It’s the circle of life. It moves us all.
Shortcuts
Even though we have finished a cycle of phosphorus you can see that our phosphorus cycle coloring sheet is not yet complete. The other component involves humans, though the impact affects quite a few different organisms.
First, we have to think back to how phosphorus enters the biosphere. If you look back to step A you will remember that phosphorus comes from rocks through the process of weathering. This is great, but it is slow. As humans, we want to speed this up. Why? Well because more phosphorus means much more beautiful lawns and flower gardens (remember, it helps to grow plants and make them flower).
At step B you will see humans mining. Why are they mining? For phosphorus of course! With this phosphorus, we can make fertilizers (I) that can be used to make our grass grow nice and quick (J). We use phosphorus-based fertilizers at our homes, in our gardens, and especially at places where the greenest lawns matter, like baseball fields and golf courses.
Take for instance a golf course, as pictured on your phosphorus color picture. When a human throws fertilizer on a lawn, the grass receives a lot of phosphorus. This keeps the grass a nice deep green color all summer long. However, not all of the phosphorus gets used. Some of it will end up collecting on the lawn, not getting used.
This wouldn’t a problem without the water cycle, but the water cycle does happen to exist. Whenever we have precipitation the water will runoff. With the water runoff, we have phosphorus runoff. This causes a lot of phosphorus to go wherever the water does, usually a pond or lake. This is where we start to see problems.
A picture of a phosphorus mining operation. Notice the color of the water.
That Dirty Water
When the phosphorus runs off into the water, there is a lot of fertilizer. This means that all of the producers in the water can grow very quickly. Way quicker than they need to. The faster organism to grow is algae. When there is too much phosphorus in the water, it will cause something called an algal bloom. What is an algal bloom?
Check out this creepy video:
Eutrophication is the named for an increase in algal life due to an increased amount of nutrient.
The Phosphorus Cycle
Name: ______Period: ______Date: ______
Questions
Color your sheet before/during/after answering each question. Make sure you color the pond green. Label the letters where appropriate from the reading.
1. Where does phosphorus come from?2. What is phosphorus used for? (name three things)
3. How is the phosphorus cycle different from the water and carbon cycle (think of the state it is in)?
4. How do plants gain phosphorus?
5. How do tertiary consumers gain phosphorus?
6. How is phosphorus “cycled” (from soil-> consumers-> soil)?
7. Why do humans mine phosphorus?
8. What do we use phosphorus for?
9. What is eutrophication?
10.When there is an increased amount of phosphorus in water, the amount of algae increases. This can sometimes cause a thick layer of green slime to form on top of a lake, blocking out the light for all other organisms below the surface. Based on what you know about the flow of energy from producers through consumers, explain which organisms may be impacted in the environment on the next page if exposed to eutrophication.