Final answer:
The difference in dissolved oxygen between the dark and light bottle in this experiment reflects the net productivity from photosynthesis, which is critical for assessing aquatic ecosystem health.
Step-by-step explanation:
In the light and dark bottle experiment, the difference in dissolved oxygen content between the dark and light bottles indicates the net productivity of the aquatic ecosystem. The dark bottle, shielded from light, allows for the measurement of oxygen consumption due to respiration, as photosynthesis is not occurring without light. Conversely, the light bottle permits both photosynthesis and respiration to occur.
Therefore, the difference in dissolved oxygen between the two bottles is attributed to the amount of oxygen produced by photosynthesis during the experiment period. This net productivity is vital in determining the health of the aquatic environment, as it reflects the balance of oxygen production and consumption, crucial for the maintenance of aerobic conditions and aquatic life support.