It's hard to say definitively which biome is the most stable as stability can be measured in various ways (resistance to change, resilience after disturbance, etc.) and varies depending on the specific factors considered.

However, when it comes to size, the largest biome on Earth is undoubtedly the ocean.

Here's why:

* Vastness: Oceans cover over 70% of the Earth's surface.

* Biodiversity: They host an incredible diversity of life, from microscopic plankton to giant whales.

* Adaptability: Marine organisms have adapted to a wide range of environments, from shallow coastal waters to the deepest trenches.

While the ocean is massive, it's important to remember that even the largest biome can be impacted by environmental changes. Climate change, pollution, and overfishing are significant threats to the ocean's health and stability.