Introduction:
The tropical rainforest is the most productive ecosystem among the options given. It is characterized by high levels of biodiversity and productivity, making it a critical component of the Earth's ecosystem.

Explanation:
1. Biodiversity:
Tropical rainforests are known for their unparalleled biodiversity. They harbor a wide variety of plant and animal species, many of which are unique to these ecosystems. The warm and humid climate, coupled with ample rainfall, creates ideal conditions for diverse life forms to thrive.

2. High Productivity:
The high productivity of tropical rainforests can be attributed to several factors:

- Abundant sunlight: The dense tree canopy allows for efficient capture and utilization of sunlight, which is essential for photosynthesis. This ensures a continuous supply of energy for plant growth.
- Moisture availability: The tropical rainforest receives substantial rainfall throughout the year, providing ample water for plant growth. This abundant moisture also supports the growth of various microorganisms and fungi, further enhancing the ecosystem's productivity.
- Nutrient cycling: The rapid decomposition of organic matter in the rainforest contributes to nutrient cycling. The warm and humid conditions accelerate the breakdown of organic material, making nutrients readily available for plant uptake. This efficient nutrient cycling sustains the high productivity of the ecosystem.
- Interactions and symbiotic relationships: The complex web of interactions between plants, animals, and microorganisms in the rainforest contributes to its productivity. Many plants rely on symbiotic relationships with fungi and other organisms to obtain nutrients more effectively. Additionally, pollination by a diverse array of insects and animals ensures successful reproduction and genetic diversity.

3. Carbon Sequestration:
Tropical rainforests play a crucial role in mitigating climate change by acting as carbon sinks. The vast vegetation in these ecosystems absorbs and stores large amounts of carbon dioxide through photosynthesis. This carbon sequestration helps regulate global climate patterns and reduces the concentration of greenhouse gases in the atmosphere.

Conclusion:
The tropical rainforest ecosystem stands out as the most productive among the options provided. Its exceptional biodiversity, high productivity, and significant role in carbon sequestration make it a vital component of the Earth's ecological balance.