There are more than a billion bacteria in just one litre of seawater. How do all of these organisms find the energy and nutrients they need to survive?
In the nutrient-rich waters near the surface of the ocean, the primary energy source is sunlight, which drives photosynthesis, the transformation of light energy into chemical energy. In much of the open ocean, however, a lack of nutrients limits photosynthesis, and in the deep ocean it ceases altogether as there is no sunlight.
