Marine Biology

1. Light and dark bottle technique

Light and dark bottle technique

A water sample is collected from a particular depth in the ocean. The oxygen content of the water sample is measured. The water from the sample is then placed in two bottles, one is transparent (light bottle) and the other is opaque (dark bottle). The two bottles are submerged at the original depth of the water sample for a period of time. Both photosynthesis and respiration will occur in the light bottle while only respiration will occur in the dark bottle. The bottles are then retrieved and the oxygen content of each bottle is measured.

Gross photosynthesis = increase in oxygen in light bottle + decrease in oxygen in dark bottle

Net photosynthesis = increase in oxygen in light bottle