AP BIO Lab 12 Dissolved Oxygen

OXYGEN AVAILABILITY Depends on: ~Temperature: Ability to hold oxygen decreases as water temp gets warmer ~ Photosynthetic Activity: In bright light, plants produce more oxygen ~ Decomposition Activity: As organic material decays, microbial processes consume oxygen ~ Mixing/turbulence: Wave action, water falls, and rapids all aerate water and increase oxygen concentration ~ Salinity: As water becomes more salty, it holds less oxygen

Temperature Warm water dissolves ~ MORE SOLIDS than cold ~ LESS GAS than cold – Reason why pop loses it’s fizz as it gets warm

PHOTOSYNTHESIS 6 CO H 2 O +Light energy C 6 H 12 O O 2 RESPIRATION C 6 H 12 O O 2 6CO H 2 O + energy → →

Waves, waterfalls, rapids all increase oxygen concentration

Maximum amount of oxygen can water hold = SATURATION What is the % saturation of a sample with 8 mg/L oxygen at 15° ? What is the % saturation of a sample with 8 mg/L oxygen at 5° ?

FIXATION OF VIALS

TITRATION Don’t fill or empty syringe past the number markings

Continue adding titrating solution until blue color changes to from purple to pale yellow/colorless. If color change does not occur when the ring on the plunger reaches the bottom of the scale, refill the titrator to the zero line and continue titrating. Keep track of volume used.

Amount of light drops off sharply with increasing depth Modeled by wrapping sample bottles in increasing layers of screen

PRIMARY PRODUCTIVITY = rate at which photosynthesizers produce organic compounds in ecosystem Can be measured by: ~ amount of CO 2 used ~ rate of sugar formation ~ rate of oxygen produced

GROSS PRODUCTIVITY = Total production of all organic compounds made by photosynthesis NET PRODUCTIVITY = Organic material that remains after cellular respiration uses some of these compounds for their energy needs

Net productivity = Gross productivity - respiraton Determined by measuring oxygen production in light Determined by measuring oxygen consumption in dark w/o Photosynthesis If measure these 2... We can calculate GROSS PRODUCTIVITY

NITRATES

NITRATES