Productivity

2.5.2 Photosynthesis & Respiration

2.5.3 Describe Energy as it moves through Ecosystems

2.5.5 Define Terms of Productivity

2.2.6 & 2.5.7 Calculate Productivity

Photosynthesis - Inputs

• carbon dioxide,
• water,
• chlorophyll
• certain visible wavelengths of light

TO PRODUCE –

• organic matter
• oxygen

http://www.1ststeps.org/Science/Photosynthesis/photosynthesis-color.jpg

Photosynthesis – energy transformation

• transformation of light energy
• into the chemical energy of organic matter

http://www.osovo.com/diagram/phototsynthesis.gif

Respiration - Inputs

• organic matter
• oxygen

TO PRODUCE

• Carbon dioxide
• Water

WITHOUT Oxygen

• carbon dioxide
• other waste products are formed

http://extension.oregonstate.edu/mg/botany/images/fig24.gif

Respiration - Outputs

• Energy is released in a form available for use by living organisms,
• but is ultimately lost as heat.

http://ec1.images-amazon.com/images/I/41s3tl36cQL.jpg

Primary Productivity

• What do “producers” gain?
• Energy-rich organic compounds from inorganic materials through photo- and chemosynthesis
• These energy rich compounds can be used in producing more of themselves either through growth or reproduction
• Production = the incorporation of energy and materials into the bodies of organisms

http://johnbokma.com/mexit/2005/01/16/nice-group-of-plants.jpg

primary productivity

• “the quantity of organic material produced, or solar energy fixed, by photosynthesis in green plants per unit time” (IB definition)
• Rate at which autotrophs synthesize new biomass

http://graphics.stanford.edu/courses/cs448c-00-fall/plants.jpg

gross primary productivity (GPP)

• Total amount of organic material fixed by autotrophs
• Result of photosynthesis (or chemosynthesis)
• CO₂ + H₂0 + light energy ⇒ glucose + O₂

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net primary productivity (NPP)�

• Rate of production of biomass potentially available to consumers (herbivores)
• Not all of the total productivity (energy) goes into making biomass (growth and reproduction)
• Some productivity is used in the autotroph’s own life processes (respiration) and this energy is ultimately lost as heat
• So, NPP = GPP - R

Productivity Review

Calculating/Measuring Primary Productivity

The Formula

• NPP = GPP – respiration
• Gain in energy or biomass per unit time AFTER respiratory losses
• GPP less the biomass or energy used by autotrophs in respiration
• Expressed as
• Energy per unit area per unit time�e.g. J/m²/yr
• Biomass added per unit area per unit time�e.g. g/m²/yr

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Light-Dark Bottle Technique

1. Measure O₂ production in�light and dark bottles
2. Light bottle: photosynthesis and respiration
3. Dark bottle: respiration only
4. Determine�

http://krupp.wcc.hawaii.edu/biol200/powerpnt/envrfact/sld013.htm

GPP = Light - Dark

NPP = Light - Initial

Respiration= Initial – Dark

Measuring Primary Productivity

1. Harvest method - measure biomass change over time and express as biomass per unit area per unit time�Destructive!
2. CO₂ assimilation - measure CO₂ uptake in photosynthesis and release by respiration
• Assume any CO₂ removed is incorporated into organic material by photosynthesis
• Use dark bottle to measure respiration in absence of photosynthesis to get GPP
• CO₂ is difficult to measure in aquatic systems

Factors that Affect Primary Productivity

1. Solar radiation: quality (type) of light�­quantity of light ­ productivity (to a point when too much light will inhibit photosynthesis)
2. Temperature: ­temp. ⇒­ productivity (to a point when high temperatures can denature enzymes)
3. CO₂: ­ CO₂ ­ productivity (since CO₂ is an input)
4. H₂O:­ H₂O ­ productivity (again since H₂O is an input)

More Factors

5. Nutrients: ­nutrients ⇒­ productivity (any food, chemical element or compound required by an organism to live, grow and reproduce, e.g. iron, magnesium, calcium, nitrate, phosphate, silicate)
6. Herbivory: grazing of autotrophs by herbivores can ⇓ productivity (e.g. sea urchins ⇓ ing productivity of kelp forest habitat)

Therefore…

• The least productive ecosystems are those with limited heat and light energy, limited water and limited nutrients
• The most productive ecosystems are those with high temperatures, lots of water, light and nutrients

secondary productivity

• Productivity of consumers
• The rate of biomass formation or energy fixation by heterotrophic organisms

http://www.danheller.com/images/LatinAmerica/Ecuador/Galapagos/tortoise-eating-big.jpg

GSP Calculations

• Total gain in energy or biomass per unit time
• Food eaten – fecal loss
• AKA Assimilation

Measuring Secondary Productivity

• Use an aquarium
• population of invertebrate herbivores (eg brine shrimps)
• or a terrarium population of invertebrate herbivores (eg silkworms)
• feed on a known producer biomass for a period of time.
• The remaining food material and feces are collected, dried and weighed.
• Net productivity might be measured as the increase in biomass of a consumer population over time.

http://www.drsfostersmith.com/images/Categoryimages/normal/p_27289_36965_aquarium.jpg