Original:  As the world's ocean is the principal component of Earth's hydrosphere, it is integral to life on Earth , forms part of the carbon cycle and water cycle, and - as a huge heat reservoir - influences climate and weather patterns.
Revised:  As the world's ocean is the principal component of Earth's hydrosphere, and therefore integral to life on Earth , forms part of the carbon cycle and water cycle, and - as a huge heat reservoir - influences climate and weather patterns.
Edit intent: clarity