Primary Productivity: Dissolved Oxygen “DO” AP Biology Lab 12

What you need to know! Dissolved oxygen availability under varying conditions Ideal conditions for maximum dissolved oxygen How to measure primary productivity by analyzing varying dissolved oxygen levels

Primary Productivity Rate organic at which organic mats are stored Mats: Carbon based organic compounds Only done by photosynthesis (PS) and chemosynthesis H2O + CO2  O2 + sugar We can measure: loss of CO2 OR gain of O2 1 mL O2 produced = .536 mg C transformed into organic compounds

Oxygen in Aquatic Environments O2 must be dissolved to be available to aquatic organisms O2 in the air 20% O2 in the water 5-10% (depending on the type of water)

DO levels change in various: Temperature Salinity pH Pollution Also creates an imbalance within the food chain Example: algae bloom

DO is highest in: Low temperature Low salinity (fresh water) Low elevation No pollution Highest DOs are in clean freshwater lakes at low altitudes

Freshwater DO Nomogram

DO, PS, and CR The productivity of living processes such as photosynthesis (PS) and cellular respiration (CR) impact DO concentrations CR uses O2 PS makes O2

Productivity Test Use live water samples (ponds/rivers/ocean) containing algae, and other PS and aerobic bacteria Incubate samples in varying levels of light intensity from 100% to 0% Measure O2 using various measuring devices: spectrometer, colorimetric scale, etc.

Results: Respiration 0% light intensity yields: No O2 produced by photosynthesis O2 consumed by cellular respiration Net loss of O2

Results: Net 100% light intensity yields: O2 produced by photosynthesis O2 consumed by cellular respiration Net gain of O2 because PS is faster than CR

Results: Gross To calculate the Primary Productivity (total amount of O2 produced) you take the amount of net O2 gained and add the amount of O2 lost during respiration

Virtual Lab http://www.phschool.com/science/biology_place/labbench/lab12/intro.html