What can you conclude about the importance of marine ecosystems to global food webs and the biosphere?

It's more accurate to define biosphere as the global ecosystem rather than global community because it just includes all the living things in a certain area regarding their different species. However, when you say ecosystem, you automatically include both living and nonliving things such as soil, water etc. So it is more accurate saying global ecosystem when you are talking about the earth-biosphere.

Explanation:

Since marine ecosystems comprise over 70% of the Earth's surface, the effect of these ecosystems on our global food web is impressive.

The oceans are an important source of oxygen for our planet and are effective in the recovery and room of carbon dioxide. Marine classes provide important ecosystem services such as the preparation of food, drugs, and livelihoods. They also support tourism and recreational projects around the world.

the answer is d.) potassium