Viruses were recognized because the causative agents of fish diseases, like infectious pancreatic necrosis and Oregon sockeye disease, within the early 1960s , and have since been shown to be liable for diseases altogether marine life from bacteria to protists, mollusks, crustaceans, fish and mammals. However, it had been not until the first 1990s that viral infections were discovered to affect marine systems beyond their role as pathogens of plants and animals, and viruses infecting unicellular organisms like bacteria (i.e., the bacteriophages) and phytoplankton were shown to possess an outsized influence on ecosystem processes. Since Karl-Heinz Moebus’ pioneering work on bacteriophage isolation and infection patterns obtained during a transect across the North Atlantic research in marine viruses has developed into a big and independent research field in marine biology, prompted by the increasing realization of the important and diverse roles of viruses within the marine ecosystem the invention that viruses were the foremost abundant biological entities in oceanic marine environments ,reaching up to 108 viruses mL−1, further stimulated marine virus research. Technical improvements in detection and enumeration of marine viruses promoted advances in additional detailed studies of viral abundance and variety at high spatial and temporal resolution. Later, the expansion of virus research to coral reefs, sediments,the deep biosphere, and freshwater environments emphasized that viruses are integrated inhabitants of all aquatic environments.