This textbook offers a basic understanding of aquatic ecotoxicology from molecular to physiological levels for graduate and advanced undergraduate students. The book covers the guidelines and lab protocols used by international organizations for ecotoxicology studies, and discusses the challenges faced by aquatic organisms in a changing climate from an ecotoxicological perspective. Readers will learn about pollutants, contaminants and chemicals of emerging concern (CECs) in aquatic environments, their impacts on environmental and human health, and what techniques can be used to curb and control their adverse impacts. The book will be useful for students in aquatic ecotoxicology, environmental pollution and marine biochemistry.