Why are oceans least productive?

Explanation

**Step-by-Step Solution:**

1. **Insufficient Sunlight:**
- The primary reason oceans are considered least productive is due to insufficient sunlight. As sunlight penetrates the water, its intensity decreases with increasing depth. This limits the photosynthetic activity of marine plants, which rely on sunlight for energy.

2. **Nutrient Deficiency:**
- Oceans are often nitrogen deficient. Nitrogen is a crucial nutrient for plant growth, and its scarcity in ocean waters limits the productivity of phytoplankton and other marine plants that form the base of the oceanic food web.

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