Answer:
The three main major groups of marine life are plankton, nekton, and benthos. Plankton float in the water while nekton swim through the water and benthos live on the ocean floor. One reason that these types of organisms live in the ocean is because they have other organism weigh heavily on them. The Plankton are known for helping all the food chains in the environment. While Nekton are known for being at the top of the food chain as predators. Benthos are oxygen eaters and are known for helping with abundance of oxygen.
Step-by-step explanation: