In freshwater lakes, microbes regulate the flow of carbon and determine if the bodies of water serve as carbon sinks or carbon sources. Algae and cyanobacteria in particular can trap and use carbon, but their capacity to do so may be impacted by viruses. Viruses exist amidst all bacteria, usually in a 10-fold excess, and are made up of various sizes ranging from giant viruses, to much smaller viruses known as virophages (which live in giant viruses and use their machinery to replicate and spread.)