Answer:
They produce oxygen and act as primary producer
Step-by-step explanation:
Marine algae are important to marine and terrestrial population because they are responsible for fixing carbon dioxide to produce oxygen as well as act as the primary producer in the marine ecosystem.
A large percentage of the oxygen available for aerobic respiration in several terrestrial organisms are produced by marine algae through the process of photosynthesis.
Also, marine algae act as the primary producer in the food chain and food web of the marine ecosystem. Without them, the food chain would be broken and biological activities would be disrupted in the marine ecosystem.