One of the most exciting research areas in environmental microbiology is the biodiversity and ecology of viruses in lakes, rivers and oceans. Viruses are the most
abundant biological particles in aquatic ecosystems. Each litre of lake or sea water will typically contain more than 10 billion viruses, encompassing a myriad of different types. Given their relatively simple structure yet biological efficiency, viruses might be considered one of the most elegantly successful forms of life in the biosphere. Each viral particle comprises an economic set of instructions that are encoded by nucleic acid and packaged within a protein coat. Once these instructions are injected by the virus into the host cell they may rest there benignly as part of the host genome, or they may reprogram the host to replicate more viral particles that are then released into the surroundings. In natural ecosystems, viruses play multiple roles: in the exchange of genetic material among microbes, in controlling the host populations that they attack, and in the biogeochemical cycling of carbon and other elements.
Electron micrographs of a variety of viruses found in the sea. From: This website
"Viruses exist wherever life is found. They are a major cause of mortality, a driver of global geochemical cycles and a reservoir of the greatest genetic diversity on Earth. In the oceans, viruses probably infect all living things, from bacteria to whales. They affect the form of available nutrients and the termination of algal blooms. Viruses can move between marine and terrestrial reservoirs, raising the spectre of emerging pathogens. Our understanding of the effect of viruses on global systems and processes continues to unfold, overthrowing the idea that viruses and virus-mediated processes are sidebars to global processes." Suttle (2005)
