Question

Which organisms reproduce rapidly, resulting eventually in a lack of oxygen? A) fish C) algae B) corals D) animal plankton

Short answer

The organisms are algae.

Step-by-step solution

Understanding the Problem

We need to identify the organism from the given options that can reproduce quickly and causes a deficit of oxygen in the environment. The options provided are fish, algae, corals, and animal plankton.

Evaluating Options

Analyze each option: - Fish: While fish reproduce, they don't rapidly deplete oxygen through reproduction. - Algae: Some algae, under certain conditions, can reproduce rapidly and lead to algal blooms, which deplete oxygen as they die and decompose. - Corals: Corals grow and reproduce, but they do not cause rapid oxygen depletion. - Animal plankton: They do not rapidly cause a lack of oxygen when they reproduce.

Conclusion

Algae, particularly certain types like blue-green algae, can reproduce explosively under nutrient-rich conditions, leading to blooms. The decomposition of these blooms by bacteria consumes oxygen, leading to hypoxic (low oxygen) conditions.

Key concepts

Oxygen Depletion

Oxygen depletion occurs when there is a significant reduction in the level of dissolved oxygen in the water. This can have harmful effects on aquatic life. Oxygen is crucial for fish and many other aquatic organisms to "breathe." When levels drop, these organisms can struggle to survive.

There are several causes of oxygen depletion:

• Natural processes, like stratification, where different water layers do not mix
• Human activities, including pollution and nutrient runoff from agriculture
• The rapid growth and decomposition of algae, known as algal blooms

Algal blooms are a common culprit. They initially produce oxygen during photosynthesis, but when they die, they are decomposed by bacteria. This bacterial breakdown uses up oxygen in the water, leading to potentially dangerous low oxygen levels.

Rapid Reproduction

Not all organisms reproduce at the same rate, but algae can reproduce very quickly under the right conditions. This is known as rapid reproduction.

Algae, in particular, can multiply exponentially when they have enough nutrients and suitable environmental conditions. When nutrients such as nitrogen and phosphorus enter water bodies, often through fertilizers, they stimulate this rapid growth.

This rapid reproduction does not happen with fish, corals, or animal plankton in the same way it does with algae. These organisms typically have longer lifecycles and different reproductive habits.

• Favorable temperatures can speed up algal reproduction.
• Sunlight and calm water conditions further boost algal growth.

As algae reproduce rapidly, they form dense algal blooms, which outcompete other organisms for resources and can have far-reaching ecological impacts.

Hypoxic Conditions

Hypoxic conditions refer to environments where the oxygen levels are too low to sustain most aquatic life. This is a dire consequence of algal blooms and their decomposition process.

When algae die, bacteria decompose them, consuming large amounts of oxygen from the water. This leads to hypoxia, a condition where oxygen levels are below 2 mg/L.

• Fish and other aquatic animals can suffocate in hypoxic conditions.
• Prolonged hypoxia can lead to "dead zones," areas where little to no life can exist.

Hypoxic areas can affect local ecosystems, killing fish and other organisms that cannot escape. This can disrupt food chains and affect human industries, like fishing and tourism. Understanding and controlling nutrient runoff can help prevent these conditions.