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

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

Calculating/Measuring Primary Productivity 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

Light-Dark Bottle Technique Measure O2 production in light and dark bottles Light bottle: photosynthesis and respiration Dark bottle: respiration only Determine http://krupp.wcc.hawaii.edu/biol200/powerpnt/envrfact/sld013.htm GPP = Light - Dark NPP = Light - Initial Respiration= Initial – Dark

Measuring Primary Productivity Harvest method - measure biomass change over time and express as biomass per unit area per unit time Destructive! 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 Solar radiation: quality (type) of light ­quantity of light ­ productivity (to a point when too much light will inhibit photosynthesis) Temperature: ­temp. Þ­ productivity (to a point when high temperatures can denature enzymes) CO2: ­ CO2 ­ productivity (since CO2 is an input) H2O:­ H2O ­ productivity (again since H2O is an input)

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