Biogeochemical cycles

Created March 2020, Offline version here
Video by Paul Anderson, also on his website Bozeman Science.

    As the Law of Conservation of energy, mass, and matter states, none can be created or destroyed. This goes with the matter that is present on Earth in that it cannot be created or destroyed. However, there are processes that allow the matter to change or convert it into different forms so that it is recycled. Since we have a finite number of resources or matter, certain processes help to matter.
    There are multiple “spheres” on Earth that matter can exist in. The lithosphere refers to the Earth or soil, the hydrosphere refers to the water on Earth, the atmosphere refers to the air, and the biosphere refers to living things. We can also differentiate these environments into the living and nonliving. Living is referred to as the and nonliving is referred to as . The biotic environment only contains the biosphere whereas the abiotic environment contains the lithosphere, hydrosphere, and atmosphere.
    Life on Earth is based on six elements: carbon, hydrogen, oxygen, nitrogen, phosphorous, and . These elements have their own cycle except for hydrogen and oxygen in that they are combined in the cycle. As the name suggests, cycles operate in a system in that the outputs become the inputs and inputs become the outputs.
    Hydrogen and oxygen are a part of the water cycle and it involves all three abiotic spheres. Water in the hydrosphere and lithosphere move to the atmosphere through evaporation from bodies of water and evapotranspiration from plants. From the atmosphere, water travels back to the lithosphere and hydrosphere through in the clouds and then as rain fall or snowfall.
    In the carbon cycle, plants and animals have the main role in transporting the carbon between the lithosphere and the atmosphere by cellular respiration in animals and photosynthesis in plants. Cellular respiration transports carbon from as carbon dioxide gas is a byproduct. transports carbon from the atmosphere to the lithosphere and the hydrosphere as plants and certain zooplankton take in carbon dioxide and uses light as a catalyst. Other ways that carbon exist within the cycle would be in factory or industrial plants where carbon dioxide is released into the air or when dead plants and animals are buried in the ground.
    The nitrogen cycle relies heavily on bacteria as they play important roles in transporting the nitrogen to and from all three spheres. Nitrogen exists in multiple forms with its dominant form as (N2) that is found in the air. For the nitrogen in the air to reach the lithosphere and hydrosphere, bacteria are needed for the job. Certain species of bacteria are able to take nitrogen from the air and convert it into ammonia (NH3). Another way nitrogen travels into the lithosphere is through fertilizers that contain nitrogen. Once the nitrogen is in the lithosphere, it undergoes several transformations via bacteria. The nitrogen fixing bacteria and fertilizers result in ammonia (NH3) and plants/animals assimilate the nitrogen.
    Once the organism dies and start decomposing, bacteria will take the ammonia and convert it into (NH4) through ammonification, then to (NO2), then to (NO3) through nitrification.
    Nitrogen is known as one of the two limiting nutrients, being the other, to life because plants depend on both elements for growth. As plants, also known as , are at the start of the flow of energy, all life depends on plants for energy. If there is an influx or a dramatic of either one of the limiting nutrients, it can cause an imbalance in the system. One such instance of this imbalance can happen with fertilizer runoff into a nearby water supply. The increased nitrogen supply will cause eutrophication where the body of water will have a sudden increase of algae. The algal bloom is unhealthy for the body of water as it consumes a lot of the oxygen required for cellular respiration in the organisms that live in the water.
    Phosphorous is the other limiting nutrient in life. This is because the phosphorous cycle is the of all the biogeochemical cycles as the atmosphere has not part in the cycle. Phosphorous is found in rocks and through , it is introduced into the soil. Similar to nitrogen, phosphorous can also be found in fertilizer, which is another method phosphorous is introduced into soil. Plants and animals assimilate the phosphorous through the water supply and when they die, decomposition will bring the phosphorous back into the soil. With all water sources leading to the ocean, the phosphorous will eventually reach the ocean and exist as sediment on the ocean floor. When there is oceanic volcanic activity, then the phosphorous may be disturbed back into the lithosphere.
    The sulfur cycle also relies on bacteria to convert sulfur into its different forms. From the ocean, bacteria convert sulfur into sulfur dioxide, a , which makes its way to the atmosphere. Sulfur dioxide is also released through volcanic activity and industrial factory byproduct. From the atmosphere, the sulfur travels back to the lithosphere via acid rain in the form of and sulfates. Plants and animals will assimilate the sulfur as intake of the sulfuric acid in the water. Once the plant or animal dies and decomposes, the sulfur will travel into the soil and into the water supply. From there, the sulfur will return to the ocean for the cycle to begin again.
    In summary, the biogeochemical cycles refer to the six essential elements of life (carbon, hydrogen, oxygen, nitrogen, phosphorous, and sulfur) and how it recycles through the earth’s biosphere, lithosphere, atmosphere, and hydrosphere. Most of the elements have their own cycle, except for hydrogen and oxygen as they refer to the water cycle, and they can share similarities in their recycling process. Nitrogen, phosphorous, and sulfur cycles rely heavily on bacteria to convert the respective elements into different forms. All of the cycles involve plants and animals to assimilate the elements through life and decomposition. Nitrogen and phosphorous are known as limiting nutrients, as the amount present in a given environment determine how much plant growth there is. The two cycles are also the slower elements to cycle through with phosphorous being the slowest as it does not involve the atmosphere.