Gross photosynthesis (oxygen produced by photosynthesis) (mgO2/l) = mean of light A & B - mean of dark A &B
(Note: Respiration and net photosynthesis can be calculated each seperately if desired by considering intial D.O. in bottles. For calculating gross photosynthesis, initial D.O. does not need to be considered because it substracts out when calculating Gross PS from Net PS and respiration)Gross Primary Productivity at each interval (mgC/m3/h) = (Oxygen produced by photosynthesis * 1000 * 0.375/1.25)/ time of incubation
Primary Productivity over depth interval (mgC/m2/h) = depth interval * (GP at top of interval + GP at bottom of interval) / 2
where:
- 1.25 is the photosynthetic quotient to adjust for conversion of sugar to other organic forms
- .375 is the ratio of moles of carbon to moles of oxygen in the reaction for photosynthesis (12/32)
(Assume GP at bottom of deepest interval is zero)
Primary Productivity throughout water column (mgC/m2/h) = sum of photosynthesis over intervals
Primary
Productivity expressed by
volume
(mgC/m3/h)= Primary
Productivity
throughout water column / photic depth
Calculations
to determine chlorophyll concentration
[Chl a] = (26.73*((abs665before - abs750before) -
(abs665after - abs750after)) *ml
of extract) / (liters
filter*path length)
Calculations
to determine zooplankton densities
Density
of zooplankton (individuals/m3)
= (individuals per subsample * sample volume / subsample volume)
volume of water sampled
where:
Volume of water sampled = depth of tow * (radius of net)2 * 3.1415
radius of net = 0.3048m