A large number of fish are suddenly found floating dead on a lake. There is no evidence of toxic dumping but you find an abundance of phytoplankton. Suggest a reason for the fish kill.

Explanation

**Step-by-Step Solution:**

1. **Observation of the Situation**: A large number of fish are found floating dead in a lake, and there is no evidence of toxic dumping. However, there is an abundance of phytoplankton present in the water.

2. **Understanding Phytoplankton**: Phytoplankton are microscopic organisms that live in aquatic environments. They are crucial for the ecosystem as they perform photosynthesis, using carbon dioxide (CO2) and releasing oxygen (O2) into the water.

3. **Role of Phytoplankton in Oxygen Dynamics**: While phytoplankton produce oxygen during the day through photosynthesis, their population can grow excessively under certain conditions, leading to a phenomenon known as algal blooms.

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