Nutrient Cycles In Ecosystems

How are Nutrients Cycled in the Biosphere? Nutrients are chemicals required for plant and animal growth and other life processes. They are constantly being recycled within Earth’s biosphere. Nutrients spend different amounts of time in stores within the atmosphere, oceans, and land. Nutrients are stored in short-term stores such as living things and the atmosphere. Nutrients are also incorporated into longer-term stores such as Earth’s crust.

How are Nutrients cycled in the biosphere? Nutrient cycles describe the flow of nutrients in and out of stores as a result of biotic and abiotic processes. Without human interference, nutrient cycles are almost perfectly balanced. Three main nutrients cycles: Carbon cycle Nitrogen cycle Phosphorous cycle

How does the Carbon Cycle Work? Carbon is an essential component of cells and life-sustaining chemical reactions. ALL living things contain carbon.  Carbon is cycled through living and decaying organisms (biosphere), the atmosphere, bodies of water (hydrosphere), and soil and rock (geosphere). Carbon moves between stores via six main processes:

1. Photosynthesis Photosynthesis is a chemical reaction that converts solar energy and atmospheric carbon dioxide gas (CO2) into chemical energy.

2. Cellular respiration Plants and animals obtain energy by converting carbohydrates and oxygen (O2) into carbon dioxide and water.

3. Decomposition Decomposers release carbon dioxide into the atmosphere through decomposition of carbon-rich organic matter in soil

4. Ocean processes Dissolved carbon dioxide is stored in oceans Marine organisms store carbon-rich carbonate in their shells, which eventually form sedimentary rock. Ocean mixing moves CO2 around the world: CO2 sinks with cold water  flows to the warm equator and evaporates into the air.

5. Volcanic Eruptions

6. Forest Fires

Human Activities and the Carbon Cycle Burning Fossil Fuels quickly reintroduces carbon into the cycle that was removed long ago and stored long term. These actions increase levels of carbon dioxide, a greenhouse gas that contributes to global climate change.  Since the Industrial Revolution, around 1850, the amount of carbon dioxide gas in the atmosphere has increased over 30 percent.

Human activities affecting carbon cycle Other activities such as land clearing, agriculture, and urban expansion also place additional carbon into the atmosphere.  Burning plants releases their stored carbon into the atmosphere  Removing plants reduces photosynthesis Burning plants releases their stored carbon into atmosphere as well as reduces photosynthesis

Effects of Excess Carbon in the Carbon Cycle Excess Green House Gases contributes to global warming. Changing one aspect of climate, such as temperature, can result in changes to other aspects, such as precipitation, wind patterns, and storm severity. Warmer Temperatures may cause:  Land and sea ice melt --> sea level rises --> coastal flooding  Warmer seawater absorbs more CO2 ---> more acidic --> coral reef    harmed Extreme Weather --> more heat waves --> possible fatalities

Check your Understanding Why is the carbon cycle important? How is carbon stored? How is carbon cycled? Name several human activities that affect the carbon cycle?

Nitrogen Cycle In our DNA and proteins Largest store is N2 gas in the atmosphere Other major stores:  oceans and organic matter in soil.  In terrestrial (land) ecosystems, living organisms, lakes and marches also store nitrogen, but in much smaller amounts.  Nitrogen is an important component of DNA and proteins, which are essential for life.  The largest store of nitrogen is the atmosphere (as nitrogen gas, N2) Other major stores include oceans and organic matter in soil.  In terrestrial (land) ecosystems, living organism, lakes and marches also store nitrogen, but in much smaller amounts. 

Nitrogen Cycle Although 78% of Earth’s atmosphere is nitrogen gas, most organisms cannot use it in this form.  Much of the nitrogen cycle involves making nitrogen available to plants and animals.

1. Nitrogen Fixation Nitrogen Fixation is the process by which nitrogen gas (N2) is converted into nitrate (NO3-) and ammonium (NH4+),  which are usable by plants.  Soil: Nitrogen fixation occurs mainly in the soil when nitrogen-fixing bacteria convert Nitrogen gas (N2) to forms usable by plants like ammonium (NH4+), Nitrite and Nitrate.  Rhizobium lives in the root nodules of legumes (peas, beans, clover, and alfalfa). The plants supply the bacteri a with sugars, Also cyanobacteria in surface waters of oceans, wetlands, and lakes. Lightning provides energy for nitrogen to react with oxygen to form these ocmounds.

1. Nitrogen Fixation Water: Cyanobacteria also fix nitrogen into ammonium Atmosphere: A very small amount of atmospheric nitrogen is fixed by lightning. Rhizobium lives in the root nodules of legumes (peas, beans, clover, and alfalfa). The plants supply the bacteri a with sugars, Also cyanobacteria in surface waters of oceans, wetlands, and lakes. Lightning provides energy for nitrogen to react with oxygen to form these ocmounds.

2. Nitrification Ammonium is converted into nitrite (NO2-) and then nitrate (NO3-) by nitrifying bacteria.

Uptake Once nitrates are made available by the nitrifying bacteria, plants can take up this usable form of nitrogen into their roots and incorporated it into plant proteins Consumers (herbivores and omnivores) incorporate nitrogen into their tissues by eating the plants.

Ammonification Some types of decomposer bacteria and fungi uptake nitrogen trapped in the proteins and DNA of dead orangisms and convert it back to ammonium (NH4+).

4. Denitrification Denitrifying bacteria convert nitrate back into atmospheric nitrogen.

Human Activities Affecting Nitrogen Cycle Burning fossil fuels and Burning organic matter (Land-clearing by burning) Both release nitrogen into the atmosphere. Nitrogen compounds eventually return to terrestrial and aquatic ecosystems as acid rain containing nitric acid (HNO3). Millions of tonnes of nitrogen are added toteh atmosphere each year in the form of nitrogen oxide (NO) and NO2. as a result of fossil fuel combustion in p

Human Activities Affecting Nitrogen Cycle Overfertilization of crops: Chemical fertilizers contain nitrogen Not all nitrogen is used by plants, Excess nitrogen can escape back into atmosphere, or be washed or leached from the soil by rain or irrigation water. Leaching = removal of a substance dissolved in soil by water Ground run-off water containing excess nitrogen enters streams and lakes. Millions of tonnes of nitrogen are added toteh atmosphere each year in the form of nitrogen oxide (NO) and NO2. as a result of fossil fuel combustion in p

Excess Nitrogen Excess nitrogen in lakes causes eutrophication (increase plant production)  Eg algal bloom – overgrowth of algae Rain carries excess nitrogen from farms, gardens, lawns into aquatic ecosystem Algae and pants at surface grow quickly, blocking sunlight form reaching deeper water Deep-water plants get no light, soon die. When they die, decomposers have lots of food and increase in number, using up all the oxygen.  As oxygen in the water is used up, aquatic organisms that need the oxygen suffocate and die. 

Algal bloom Excess algae growth can deprive other aquatic plants of sunlight and of oxygen. When algae die, the oxygen used in decomposition also deprives aquatic animals of oxygen and can lead to the death of all fish in a lake.  Rain carries excess nitrogen from farms, gardens, lawns into aquatic ecosystem Algae and pants at surface grow quickly, blocking sunlight form reaching deeper water Deep-water plants get no light, soon die. When they die, decomposers have lots of food and increase in number, using up all the oxygen.  As oxygen in the water is used up, aquatic organisms that need the oxygen suffocate and die. 

Algal Bloom Some algae produce neurotoxin that enter the food web to shellfish, seabirds, marine mammals and humans. Eg. Red Tide Rain carries excess nitrogen from farms, gardens, lawns into aquatic ecosystem Algae and pants at surface grow quickly, blocking sunlight form reaching deeper water Deep-water plants get no light, soon die. When they die, decomposers have lots of food and increase in number, using up all the oxygen.  As oxygen in the water is used up, aquatic organisms that need the oxygen suffocate and die. 

Check your Understanding Why is the nitrogen cycle important? How is nitrogen stored? How is nitrogen cycled? Name several human activities that affect the nitrogen cycle?

Phosphorous In plants phosphorous is important for healthy root, stem and seed development. In animals it is an essential element in our bones as well as a main component in the energy molecule, ATP, produced by our mitochondria. Not found in atmosphere

Phosphorous In the environment it is found (stored long-term) in phosphate (PO4-) rock and sediments on the ocean floor. Living organisms cycle nutrients very quickly compared to geologic features.

Phosphorous Cycle Weathering (the process of breaking down rock into smaller fragments) is the main method of cycling phosphorous. Uptake - Plant take up phosphorous from the soil by their roots. Decomposition - bacteria release phosphorous back into the soil by breaking down dead organisms. Geologic Uplift - Excess phosphorous run-off will collect as sediment in the bottoms of lakes and oceans where it eventually forms sedimentary rock for millions of years until a major geological event uncovers buried rock in mountain formation

Human Activity and Phosphorous Cycle Phosphate rock is mined for fertilizers and detergents such as those used in dishwashers Slash and burn also releases excess P Just like too much nitrogen in lake water, it can cause fish to die.

Excess Phosphorous Also leads to algal blooms, 

Dead Zones Dead zones are hypoxic (low-oxygen) areas in the world's oceans and large lakes, caused by "excessive nutrient pollution from human activities coupled with other factors that deplete the oxygen required to support most marine life in bottom and near-bottom water. Because most organisms need oxygen to live, few organisms can survive in hypoxic conditions. That is why these areas are called dead zones. Dead zones occur because of a process called eutrophication, which happens when a body of water gets too many nutrients, such as phosphorus and nitrogen.

Dead Zone in Gulf of Mexico

Check your Understanding Why is the phosphorous cycle important? How is phosphorous stored? How is phosphorous cycled? Name several human activities that affect the phosphorous cycle?

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