Energy Flow and Nutrient Cycling

What are ecosystem?

• One or more communities of living organisms with their non-living physical and chemical environments. 

• Ecosystem ecology emphasizes the storage and transfer of energy and matter.

  • Various chemical elements essential to life (C, N, P) 

What is primary productivity?

• The rate at which solar or chemical energy is captured and converted into chemical bonds by photosynthesis or chemosynthesis

What does primary productivity tell you?

• Primary productivity tells us how much energy is available in an ecosystem. 

• Ex: 1 percent of the sun's energy is converted into food resources. 

Why is measuring primary productivity important?

Measuring primary productivity can help ecologists track changes to ecosystems through time and compare ecosystems across the world.

How do primary producers harness energy?

• From the environment and form the foundation of food webs.

  • Common in photosynthesis, where producers harvest energy from sunlight

  • Chemosynthesis is also possible (i.e. deep thermal vents (sulfide gas)). 

Producers use energy for respiration, growth, and reproduction: What does the amount used for growth and reproduction represent?

• Represents the energy that is available to consumers

What are common ways to measure primary productivity?

• Biomass (NPP): Change in the biomass of producers over time

• Respiration: Change in carbon dioxide concentrations or oxygen concentrations over time. 

What are the two types of primary productivity?

• Gross Primary Productivity (GPP)

• Net Primary Productivity (NPP)

What is Gross Primary Productivity (GPP)?

The rate at which energy is captured and assimilated by producers in an area.

What is Net Primary Productivity (NPP)?

The rate at which energy is assimilated by producers and converted into producer biomass in an area.

What is ecological efficiency?

Also known as food chain efficiency- the percentage of net production from one trophic level compared to the next lower trophic level. 

Ecological Efficiency= net production energy of a trophic level (J)/ net production energy of the next lower trophic level (J). 

What are three steps of energy transfer between trophic levels?

• Consumption= eating it

• Assimilation= incorporating it

• Production= growing and reproducing with it 

What role does water play in nutrient cycling?

Water moves elements around in a dissolved state, affecting nutrient cycling globally. 

How is nitrogen involved in nutrient cycling?

• Nitrogen is an important component of amino acids (the building blocks of proteins) and nucleic acids (the building blocks of DNA). 

• Exists in many forms and has a complex cycle. 

How can producers take in nitrogen?

Producers can take up nitrogen from the soil or water as either ammonium or nitrates.

What are dead zones?

areas in oceans, lakes, and other bodies of water with such low oxygen levels that most marine life cannot survive. They are primarily caused by excessive nutrient pollution from sources like agricultural and urban runoff, which leads to rapid algae growth.

Where are dead zones common? 

Common where freshwater meets ocean due to surface runoff of excess nutrients (primarily phosphorous)