Lab #12 dO 2 & Primary Productivity

Aquatic Primary Producers

Gall Ball Parasitism

Decomposer

Decomposers

Terrestrial & Aquatic Producers

Primary Productivity A good measure of the health of an ecosystem is its primary productivity A way you can do this is to measure the amount of activity performed by the autotrophs of the system.

Remember that some captured photosynthetic energy is stored in plant tissue, and that plants themselves are eaten by the heterotrophs… So, the total amount of photosynthesis is a measure of the first (primary) energy stored in an ecosystem

The Oxygen Cycle Atmospheric O 2 and dissolved O 2 Cellular Respiration Photo- synthesis H2OH2O CO 2

Productivity Gross productivity - total amount of energy photosynthesized by the autotrophs… Net productivity - total amount of energy available to the heterotrophs How can productivity be measured ?

The net equation for photosynthesis: 6CO H 2 O > C 6 H 12 O 6 + 6O 2 So, you can simply measure the amount of O 2 produced, right? Well, not quite. The plant also performs cellular respiration: C 6 H 12 O 6 + 6O > 6CO H 2 O It makes a lot of energy, uses some, then provides the net energy to the heterotrophs... Photosynthesis & Respiration

Plant in light: Measure O 2 produced after photosynthesis and respiration…NET Gross Productivity Plant in dark: Measure O 2 used up in cellular respiration... Calculate: Subtract dark measurement from light measurement to get gross primary productivity