ZOL 355 Lecture 9 Outline of Last Lecture I Primary Production Outline of Current Lecture I Discuss four methods for estimating GPP NPP and R II Example calculations for estimating GPP NPP R Current Lecture I II III IV Measuring Primary Production a Using chambers to measure NPP and R b CO2 measured during day and night in closed chamber c NPP R GPP i NPP CO2 initial CO2 time ii these measurements taken in light Estimating GPP NPP and R from O2 concentration a measured in light and dark bottles b water from photic zone placed in clear light or opaque dark bottles c three bottles are prepared 2 light and 1 dark bottle d O2 of one light bottle is measured immediately initial bottle e The second light bottle light bottle one dark bottle dark bottle are returned to the water column for a period of time f Each bottle has a unique significance i Bottle 1 O2 measured immediately initial bottle oxygen concentration at start of experiment ii Bottle 2 dark bottle respiration only iii Bottle 3 light bottle net result of respiration photosynthesis g After several hours in the water column the O2 concentration in the light dark bottle are measured compared to the O2 concentration in the initial bottle Estimating R How much of the O2 in the initial bottle has been used in respiration a Compare the initial and the dark bottle b R O2 initial O2 dark time c Respiration Utilizes Oxygen Causes a Decrease in Oxygen Concentration Within the Dark Bottle Estimating NPP a The light bottle contains O2 that was initially present and O2 that results after respiration and photosynthesis have occurred b If we account for the O2 initially present initial bottle we have NPP c NPP light initial V VI d NPP O2 light O2 initial time e NPP When photosynthesis predominates over respiration there is an increase in O2 in light bottle relative to initial bottle f NPP O2 light O2 initial time EXAMPLE a Initial O2 10 mg L b Dark bottle O2 4 mg L c Light bottle O2 11 mg L d Incubation Time 24 hr e R O2 initial O2 dark time i 10 mg L 4 mg L 24 hr ii 6 mg L 24 hr iii 0 25 mg L hr Harvest method to estimate NPP a Harvest is the biomass produced in year b Problems i Difficult to measure below ground biomass ii Grazing must be constrained