The article says in the section entitled "Human Impacts on the Carbon Cycle" that more carbon dioxide dissolving in water is not a good thing because it produces bicarbonate along with H+ ions which can in turn reduce the levels of bicarbonate. Am I missing something? The only way increased carbon dioxide will lead to more H+ ions in the water is through producing bicarbonate. All that will happen is that same bicarbonate will be taken out by its own H+ ions, which if they weren't there, the bicarbonate wouldn't be there either. So what's the big deal? Also, why can't the H+ ions dissolve into the atmosphere?

when carbon dioxide dissolves in water it produces hydrogen ion. the water becomes acidic because of the hydrogen ions dissolved in it

what will happen if we did not had athmosphere?

We probably wouldn't able to breathe - not just humans but other oxic and anoxic organisms. Also, Earth would look like it looked way before atmosphere formed - full fo craters, volcanoes, extreme thunderstorms, extreme drought, UV light from the sun, etc... Eroded lithosphere and unfriendly environment.

how many carbon dioxide are there in the atmosphere

According to NASA§ the total mass of earth's atmosphere is 5.1 x 10¹⁸ kg. As of 2018 the fraction of the atmosphere that is CO₂ is 622 parts per million by mass (409 ppm by volume). So, since the mass of CO₂ is ~44 g/mol and using Avogadro's number: 5.1 x 10²¹ g ⋅ 6.22 x 10⁻⁴ / 44 g/mol ⋅ 6.022 x 10²³ molecule/mol ≈ 4.3 x 10⁴⁰ molecules of CO₂ § https://nssdc.gsfc.nasa.gov/planetary/factsheet/earthfact.html

Explain Carbon reservoirs

There are four carbon reservoirs 1. In rocks (this includes fossil fuels) 2. Dissolved in ocean water. 3. As plants, sticks, animals, and soil (which can be lumped together and called the land biosphere) 4. As a climate-warming gas in the atmosphere.

What are the similarities and differences between carbon cycle and energy flow?

Comparison of different scales. I'd understand comparisons of the Carbon cycle to the Nitrogen cycle, but the comparison to energy flow... Energy flow is something that happens and inseparable from element cycles in the biosphere.

Hi! I just had a quick question: Is calcium carbonate limestone?

Limestone is largely made of the mineral forms of Calcium Carbonate , but also has few other particles such as clay and quartz.

What is biogeochemical cycle?

A biogeochemical cycle is a pathway by which certain chemical (in this case Carbon) travels through Earth (abiotic and biotic).

Main content

The carbon cycle

Google Classroom

Learn how carbon moves through Earth's ecosystems and how human activities are altering the carbon cycle.

Key points

Carbon is an essential element in the bodies of living organisms. It is also economically important to modern humans, in the form of fossil fuels.
Carbon dioxide—start text, C, O, end text, start subscript, 2, end subscript—from the atmosphere is taken up by photosynthetic organisms and used to make organic molecules, which travel through food chains. In the end, the carbon atoms are released as start text, C, O, end text, start subscript, 2, end subscript in respiration.
Slow geological processes, including the formation of sedimentary rock and fossil fuels, contribute to the carbon cycle over long timescales.
Some human activities, such as burning of fossil fuels and deforestation, increase atmospheric start text, C, O, end text, start subscript, 2, end subscript and affect Earth's climate and oceans.

Carbon: building block and fuel source

About 18% of your body consists of carbon atoms, by mass, and those carbon atoms are pretty key to your existence!start superscript, 1, end superscript Without carbon, you wouldn't have the plasma membranes of your cells, the sugar molecules you use for fuel, or even the start text, D, N, A, end text that carries instructions to build and run your body.

Carbon is part of our bodies, but it's also part of our modern-day industries. Carbon compounds from long-ago plants and algae make up the fossil fuels, such as coal and natural gas, that we use today as energy sources. When these fossil fuels are burned, carbon dioxide—start text, C, O, end text, start subscript, 2, end subscript—is released into the air, leading to higher and higher levels of atmospheric start text, C, O, end text, start subscript, 2, end subscript. This increase in start text, C, O, end text, start subscript, 2, end subscript levels affects Earth's climate and is a major environmental concern worldwide.

Let's take a look at the carbon cycle and see how atmospheric start text, C, O, end text, start subscript, 2, end subscript and carbon use by living organisms fit into the bigger picture of carbon cycling.

The carbon cycle

The carbon cycle is most easily studied as two interconnected subcycles:

One dealing with rapid carbon exchange among living organisms
One dealing with long-term cycling of carbon through geologic processes

Although we will look at them separately, it's important to realize these cycles are linked. For instance, the same pools of atmospheric and oceanic start text, C, O, end text, start subscript, 2, end subscript that are utilized by organisms are also fed and depleted by geological processes.

As a brief overview, carbon exists in the air largely as carbon dioxide—start text, C, O, end text, start subscript, 2, end subscript—gas, which dissolves in water and reacts with water molecules to produce bicarbonate—start text, H, C, O, end text, start subscript, 3, end subscript, start superscript, minus, end superscript. Photosynthesis by land plants, bacteria, and algae converts carbon dioxide or bicarbonate into organic molecules. Organic molecules made by photosynthesizers are passed through food chains, and cellular respiration converts the organic carbon back into carbon dioxide gas.

Longterm storage of organic carbon occurs when matter from living organisms is buried deep underground or sinks to the bottom of the ocean and forms sedimentary rock. Volcanic activity and, more recently, human burning of fossil fuels bring this stored carbon back into the carbon cycle. Although the formation of fossil fuels happens on a slow, geologic timescale, human release of the carbon they contain—as start text, C, O, end text, start subscript, 2, end subscript—is on a very fast timescale.

The biological carbon cycle

Carbon enters all food webs, both terrestrial and aquatic, through autotrophs, or self-feeders. Almost all of these autotrophs are photosynthesizers, such as plants or algae.

Autotrophs capture carbon dioxide from the air or bicarbonate ions from the water and use them to make organic compounds such as glucose. Heterotrophs, or other-feeders, such as humans, consume the organic molecules, and the organic carbon is passed through food chains and webs.

How does carbon cycle back to the atmosphere or ocean? To release the energy stored in carbon-containing molecules, such as sugars, autotrophs and heterotrophs break these molecules down in a process called cellular respiration. In this process, the carbons of the molecule are released as carbon dioxide. Decomposers also release organic compounds and carbon dioxide when they break down dead organisms and waste products.

Carbon can cycle quickly through this biological pathway, especially in aquatic ecosystems. Overall, an estimated 1,000 to 100,000 million metric tons of carbon move through the biological pathway each year. For context, a metric ton is about the weight of an elephant or a small car!start superscript, 2, comma, 3, comma, 4, end superscript

The geological carbon cycle

The geological pathway of the carbon cycle takes much longer than the biological pathway described above. In fact, it usually takes millions of years for carbon to cycle through the geological pathway. Carbon may be stored for long periods of time in the atmosphere, bodies of liquid water—mostly oceans— ocean sediment, soil, rocks, fossil fuels, and Earth’s interior.

The level of carbon dioxide in the atmosphere is influenced by the reservoir of carbon in the oceans and vice versa. Carbon dioxide from the atmosphere dissolves in water and reacts with water molecules in the following reactions:

start text, C, O, end text, start subscript, 2, end subscript, plus, start text, H, end text, start subscript, 2, end subscript, start text, O, end text, \rightleftharpoons, start text, H, end text, start subscript, 2, end subscript, start text, C, O, end text, start subscript, 3, end subscript, \rightleftharpoons, start text, H, C, O, end text, start subscript, 3, end subscript, start superscript, minus, end superscript, plus, start text, H, end text, start superscript, plus, end superscript, \rightleftharpoons, start text, C, O, end text, start subscript, 3, end subscript, start superscript, 2, minus, end superscript, plus, 2, start text, H, end text, start superscript, plus, end superscript

The carbonate—start text, C, O, end text, start subscript, 3, end subscript, start superscript, 2, minus, end superscript—released in this process combines with start text, C, a, end text, start superscript, 2, plus, end superscript ions to make calcium carbonate—start text, C, a, C, O, end text, start subscript, 3, end subscript—a key component of the shells of marine organisms.start superscript, 5, end superscript When the organisms die, their remains may sink and eventually become part of the sediment on the ocean floor. Over geologic time, the sediment turns into limestone, which is the largest carbon reservoir on Earth.

On land, carbon is stored in soil as organic carbon from the decomposition of living organisms or as inorganic carbon from weathering of terrestrial rock and minerals. Deeper under the ground are fossil fuels such as oil, coal, and natural gas, which are the remains of plants decomposed under anaerobic—oxygen-free—conditions. Fossil fuels take millions of years to form. When humans burn them, carbon is released into the atmosphere as carbon dioxide.

Another way for carbon to enter the atmosphere is by the eruption of volcanoes. Carbon-containing sediments in the ocean floor are taken deep within the Earth in a process called subduction, in which one tectonic plate moves under another. This process forms carbon dioxide, which can be released into the atmosphere by volcanic eruptions or hydrothermal vents.

Human impacts on the carbon cycle

Global demand for Earth’s limited fossil fuel reserves has risen since the beginning of the Industrial Revolution. Fossil fuels are considered a nonrenewable resource because they are being used up much faster than they can be produced by geological processes.

When fossil fuels are burned, carbon dioxide—start text, C, O, end text, start subscript, 2, end subscript—is released into the air. Increasing use of fossil fuels has led to elevated levels of atmospheric start text, C, O, end text, start subscript, 2, end subscript. Deforestation—the cutting-down of forests—is also a major contributor to increasing start text, C, O, end text, start subscript, 2, end subscript levels. Trees and other parts of a forest ecosystem sequester carbon, and much of the carbon is released as start text, C, O, end text, start subscript, 2, end subscript if the forest is cleared.start superscript, 6, end superscript

Some of the extra start text, C, O, end text, start subscript, 2, end subscript produced by human activities is taken up by plants or absorbed by the ocean, but these processes don't fully counteract the increase. So, atmospheric start text, C, O, end text, start subscript, 2, end subscript levels have risen and continue to rise. start text, C, O, end text, start subscript, 2, end subscript levels naturally rise and fall in cycles over long periods of time, but they are higher now than they have been in the past 400,000 years, as shown in the graph below:

[Why do the carbon dioxide levels cycle up and down over the years?]

Why does it matter that there is lots of start text, C, O, end text, start subscript, 2, end subscript in the atmosphere? start text, C, O, end text, start subscript, 2, end subscript is a greenhouse gas. When in the atmosphere, it traps heat and keeps it from radiating into space. Based on extensive evidence, scientists think that elevated levels of start text, C, O, end text, start subscript, 2, end subscript and other greenhouse gases are causing pronounced changes in Earth's climate. Without decisive changes to reduce emissions, Earth's temperature is projected to increase by 1 to 5degreesC by the year 2100.start superscript, 8, end superscript

Also, while uptake of excess carbon dioxide by the oceans might seem good from a greenhouse gas perspective, it may not be good at all from the perspective of sea life. As we saw above, start text, C, O, end text, start subscript, 2, end subscript dissolved in seawater can react with water molecules to release start text, H, end text, start superscript, plus, end superscript ions. So, dissolving more start text, C, O, end text, start subscript, 2, end subscript in water causes the water to become more acidic. More acidic water can, in turn, reduce start text, C, O, end text, start subscript, 3, end subscript, start superscript, 2, minus, end superscript concentrations and make it harder for marine organisms to build and maintain their shells of start text, C, a, C, O, end text, start subscript, 3, end subscript.start superscript, 9, end superscript Both increasing temperatures and higher acidity can harm sea life and have been linked to coral bleaching.

The debate about the future effects of increasing atmospheric carbon on climate change focuses on fossils fuels. However, scientists must take natural processes, such as volcanoes, plant growth, soil carbon levels, and respiration, into account as they model and predict the future impact of this increase.

[Attribution and references]

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Isaac D. Cohen
Posted 5 years ago. Direct link to Isaac D. Cohen's post “The article says in the s...”
The article says in the section entitled "Human Impacts on the Carbon Cycle" that more carbon dioxide dissolving in water is not a good thing because it produces bicarbonate along with H+ ions which can in turn reduce the levels of bicarbonate. Am I missing something? The only way increased carbon dioxide will lead to more H+ ions in the water is through producing bicarbonate. All that will happen is that same bicarbonate will be taken out by its own H+ ions, which if they weren't there, the bicarbonate wouldn't be there either. So what's the big deal?

Also, why can't the H+ ions dissolve into the atmosphere?
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(5 votes)
Answer
- samuelyung758
  Posted 10 months ago. Direct link to samuelyung758's post “when carbon dioxide disso...”
  when carbon dioxide dissolves in water it produces hydrogen ion. the water becomes acidic because of the hydrogen ions dissolved in it
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  (2 votes)
🎆M🎆A🎆R🎆I🎆A🎆P🎆A🎆U🎆L🎆A🎆
Posted 3 years ago. Direct link to 🎆M🎆A🎆R🎆I🎆A🎆P🎆A🎆U🎆L🎆A🎆's post “what will happen if we di...”
what will happen if we did not had athmosphere?
Button navigates to signup pageComment on 🎆M🎆A🎆R🎆I🎆A🎆P🎆A🎆U🎆L🎆A🎆's post “what will happen if we di...”
(4 votes)
Answer
- Ivana - Science trainee
  Posted 3 years ago. Direct link to Ivana - Science trainee's post “We probably wouldn't able...”
  We probably wouldn't able to breathe - not just humans but other oxic and anoxic organisms.
  
  Also, Earth would look like it looked way before atmosphere formed - full fo craters, volcanoes, extreme thunderstorms, extreme drought, UV light from the sun, etc...
  
  Eroded lithosphere and unfriendly environment.
  Button navigates to signup page
  (6 votes)
iyanapierre2003
Posted 5 years ago. Direct link to iyanapierre2003's post “how many carbon dioxide a...”
how many carbon dioxide are there in the atmosphere
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(2 votes)
Answer
- tyersome
  Posted 5 years ago. Direct link to tyersome's post “According to NASA§ the to...”
  According to NASA§ the total mass of earth's atmosphere is 5.1 x 10¹⁸ kg.
  
  As of 2018 the fraction of the atmosphere that is CO₂ is 622 parts per million by mass (409 ppm by volume).
  
  So, since the mass of CO₂ is ~44 g/mol and using Avogadro's number:
  5.1 x 10²¹ g ⋅ 6.22 x 10⁻⁴ / 44 g/mol ⋅ 6.022 x 10²³ molecule/mol ≈ 4.3 x 10⁴⁰ molecules of CO₂
  
  § https://nssdc.gsfc.nasa.gov/planetary/factsheet/earthfact.html
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  (9 votes)
Lamiaa Hatem
Posted 6 years ago. Direct link to Lamiaa Hatem's post “Explain Carbon reservoirs”
Explain Carbon reservoirs
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(2 votes)
Answer
- Benjamin Hsieh
  Posted 6 years ago. Direct link to Benjamin Hsieh's post “There are four carbon res...”
  There are four carbon reservoirs
  1. In rocks (this includes fossil fuels)
  2. Dissolved in ocean water.
  3. As plants, sticks, animals, and soil (which can be lumped together and called the land biosphere)
  4. As a climate-warming gas in the atmosphere.
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  (8 votes)
Kaitlyn Hults
Posted 6 years ago. Direct link to Kaitlyn Hults's post “Does the carbon cycle hap...”
Does the carbon cycle happen in human bones? (for example, after death)
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(3 votes)
Answer
- Hugo Lerming Lerminguez
  Posted 6 years ago. Direct link to Hugo Lerming Lerminguez's post “maybe to a tiny extent as...”
  maybe to a tiny extent as there is a lot of organic matter inside of bones (think marrow), but the main component of bone is hydroxylapatite (aka hydroxyapatite) and this has no carbon in the repeating formula unit (Ca5(PO4)3(OH)). this is probably why bones last a long time whereas the "meatier" parts of the animal essential disappear.
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  (1 vote)
andreancheng
Posted 4 years ago. Direct link to andreancheng's post “What are the similarities...”
What are the similarities and differences between carbon cycle and energy flow?
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(2 votes)
Answer
- Ivana - Science trainee
  Posted 4 years ago. Direct link to Ivana - Science trainee's post “Comparison of different s...”
  Comparison of different scales. I'd understand comparisons of the Carbon cycle to the Nitrogen cycle, but the comparison to energy flow...
  
  Energy flow is something that happens and inseparable from element cycles in the biosphere.
  Button navigates to signup page
  (2 votes)
cookiemonster🍪
Posted 3 years ago. Direct link to cookiemonster🍪's post “Hi! I just had a quick qu...”
Hi! I just had a quick question:

Is calcium carbonate limestone?
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(2 votes)
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- Arpit M.
  Posted 3 years ago. Direct link to Arpit M.'s post “Limestone is largely made...”
  Limestone is largely made of the mineral forms of Calcium Carbonate , but also has few other particles such as clay and quartz.
  Comment on Arpit M.'s post “Limestone is largely made...”
  (2 votes)
maria.piplos
Posted 4 years ago. Direct link to maria.piplos's post “how does a carbon molecul...”
how does a carbon molecule from the deep ocean travel from an animal?
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- The Lone Fox
  Posted 3 years ago. Direct link to The Lone Fox's post “Deep sea oil drills take ...”
  Deep sea oil drills take it, an oil spill occurs, it winds up on and in the sea, and is absorbed by marine lifeforms.
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Gwendolyn Davis
Posted 3 years ago. Direct link to Gwendolyn Davis's post “what is the humans affect...”
what is the humans affect in water why cant we breath in water
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Dil Bahadur Tamang
Posted 4 years ago. Direct link to Dil Bahadur Tamang's post “What is biogeochemical cy...”
What is biogeochemical cycle?
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- Ivana - Science trainee
  Posted 4 years ago. Direct link to Ivana - Science trainee's post “A biogeochemical cycle is...”
  A biogeochemical cycle is a pathway by which certain chemical (in this case Carbon) travels through Earth (abiotic and biotic).
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  (2 votes)

Biology library

Course: Biology library > Unit 28

The carbon cycle

Key points

Carbon: building block and fuel source

The carbon cycle

The biological carbon cycle

The geological carbon cycle

Human impacts on the carbon cycle

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