Plants and algae form an important basis of all marine ecosystems. They provide nutrients to animals that eat them and also create oxygen for humans and animals to breathe. This lower elementary title covers the diversity of marine plants and algae that exist as well as the processes they undergo to grow and thrive. Photosynthesis is explained in easy-to-understand language, as is the role of plants and algae in food chains and food webs. Finally, the importance of sea plants and algaeand threats to their existenceis addressed in a timely discussion on global warming.