Aquatic plants that float on water in a pond can reproduce rapidly, covering the surface of the pond. These aquatic plants can impact the oxygen levels in the pond when when they die. Sometimes the oxygen levels are so severely impacted that there is no longer enough oxygen in the water for fish to survive.
Why is there not enough oxygen for the fish to survive when a large population of the aquatic plants die?
a. The bacteria use oxygen in the water as they decompose the plants.
b. The dead plants are covering the surface of the pond and blocking the sunlight.
c. The dead plants create a blanket on the top of the pond causing the water to warm up.
d. The plants produce carbon dioxide instead of oxygen when they die.
I think it is A but all of them seem correct
You're on the right track! In this case, all of the options presented could potentially contribute to a decrease in oxygen levels, but the most direct reason why there might not be enough oxygen for the fish to survive when a large population of aquatic plants dies is option A: The bacteria use oxygen in the water as they decompose the plants.
When the aquatic plants die, bacteria decompose them through the process of decomposition. Decomposition requires oxygen, and as the bacteria break down the dead plant matter, they consume the available oxygen in the water. This reduction in oxygen levels can be detrimental to fish and other aquatic organisms that rely on oxygen to survive.
Option B, the dead plants covering the surface of the pond and blocking sunlight, can indirectly contribute to oxygen depletion. If sunlight is blocked, it can hinder the process of photosynthesis in the remaining live plants in the pond, which can result in a decrease in oxygen production. However, this option is not as directly linked to the question as option A.
Option C, the dead plants creating a blanket on the top of the pond causing the water to warm up, is unrelated to the decrease in oxygen levels. While a warm water temperature can potentially lower the dissolved oxygen content in water, this is not the main reason why there may not be enough oxygen for fish to survive in this scenario.
Option D, the plants producing carbon dioxide instead of oxygen when they die, is also not a primary factor in the depletion of oxygen levels. While plants do produce carbon dioxide through respiration when they are alive, the decomposition process does not convert all the produced oxygen into carbon dioxide.
In summary, while all of the presented options can have some influence on oxygen levels in a pond, option A, the bacteria using oxygen as they decompose the dead plants, is the most directly related reason why there might not be enough oxygen for fish to survive in this specific scenario.