The BOD light and dark bottle method measures primary productivity by determining changes in oxygen concentrations over time. Photosynthesis (light bottle) produces oxygen, while respiration (dark bottle) consumes oxygen. An initial bottle of water is taken and chemically fixed to determine the initial oxygen concentration. After a specified time (30 minutes to 24 hours) chosen to incubate the samples, the samples are chemically fixed like the initial bottle and DO is calculated and the difference in oxygen produced in the light bottle (from photosynthesis and respiration) to the oxygen consumed in the dark bottle (only respiration) is gross primary productivity. The difference in DO between the light bottle and the initial bottle is net productivity, and the difference between the initial and the dark bottle is respiration. A measure of oxygen production over time is a means to calculate the amount of carbon bound in organic compounds over a period of time measured as mg Oxygen/L = ppm Oxygen. The concentration of carbon fixed in photosynthesis can be determined by mL Oxygen/L x 0.536 = mg Carbon fixed/L where mL oxygen/L = mg oxygen/L x 0.698.
Secchi disk measures the transparency of water and can be affected by turbidity as well as plankton.
The use of corning flasks would be to culture cells in a medium.
A water sampler would be useful to collect water at a specific depth in a body of water for nutrient analyses, chlorophyll analyses, or taxonomic data of the plankton at depth to create a vertical distribution of zooplankton or phytoplankton at that depth at that specific time. I don't think I've ever used a water sampler to determine primary productivity, mostly depth profiles. DO can be obtained, but it would only be at that specific depth at a specific time, so you wouldn't be able to measure productivity (over time) unless you put those samples into BOD bottles.
For primary productivity we use Light and Dark bottles and do titrations for DO concentrations. We take an integrated water sample, mix it well in a bucket, and fill the BOD bottles. The most accurate DO concentrations would be to incubate the bottles in the water where the samples were taken to get an idea of what light concentrations, temperature, or other ambient factors (like cloud cover) affect photosynthesis.
I agree with Cathleen, because I have this method many times
depending of the place where you are measuring and the equipment you have available. For example, is not the same measuring in open ocean than in a lake. The in situ incubated BOD method cannot be used in the ocean, but in a lake where you expect to have oxygen production in a very short period of time. C14 or stable isotopes of oxygen is more appropiate for ocean samples. Get familiar with several techniques and choose the one you can apply in your environment. This recient paper shows all the PP methods Book Aquatic Primary Productivity Field Protocols for Satellite V...
I have only been engaged in measurement of phytoplankton primary production using C14 and light and dark bottles as introduced by the Danish Dr. Steeman Nielsen years back.
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