Aquatic ecosystems are vast reserves of water biodiversity, essential for the maintenance of ecological balance in the environment. Aquatic ecosystems are primarily of two types- marine and freshwater. All water bodies are part of the aquatic ecosystem. They are essential for recycling of nutrients, purification of water, flood attenuation, recharge of groundwater and provision of habitat for different species of animals and plants. The health of an aquatic ecosystem is affected by the physical, chemical or biological changes in the environment. Overfishing, water pollution, climate change and coastal land encroachment have significant negative consequences on the aquatic ecosystem. This book is a compilation of chapters that discuss the most vital concepts and emerging trends in the field of aquatic ecosystem. Some of the diverse topics covered in this book address the varied branches that fall under this category. With state-of-the-art inputs by acclaimed experts in this field, this book targets marine biologists, oceanographers, limnologists, aquatic ecologists as well as students and researchers associated with this domain.