Question: What percentage of the ocean is covered by plants?

Emma Markham answered on 16 Jun 2019:

It’s very hard to calculate the exact percentage, because most of the plants are too small to see without a microscope, and it varies between different regions of the ocean.

The majority of the ‘plants’ in the ocean are plankton, which are microscopic organisms that float freely with oceanic currents and in other bodies of water. Plankton is made up of tiny plants (called phytoplankton) and tiny animals (called zooplankton). Plankton produce 50 to 85 percent of the oxygen in Earth’s atmosphere! So they are really important to life on Earth. They are also a vital food source of whales and fish.

Other ‘plants’ include algae, seaweed and seagrass. These tend to only be in shallow water (as the sunlight cannot easily pass through water, so the further down in the ocean the darker it is, and plants need light to grow so cannot grow in the bottom of the ocean). and so we normally see seaweed and seagrass in coastal regions, this is an important food source for turtles and other marine animals.