English: Viruses are a “regulator” of the global ecosystem C cycle network
The gray arrows in the upper right corner of the diagram represent influence and the red arrow represents regulation. The arrows show the roles that viruses play in the traditional food web, the “microbial loop” and the C cycle network of ecosystems. Light green arrows represent the traditional food web, white arrows represent the microbial loop, white dotted arrows represent the contribution rate of C produced by viral lysing of bacteria to the ecosystem DOC pool, and gray arrows represent the intersystem migration C process. Additionally, C reserves and the C exchange volume are indicated in orange or yellow font. The schematic diagram of the freshwater ecosystem was similar to that of the marine ecosystem and is not shown separately. The “microbial loop” is an important supplement to the classic food chain, wherein dissolved organic matter (DOM) is ingested by heterotrophic “planktonic” bacteria during secondary production. These bacteria are then consumed by protozoa, copepods and other organisms, and eventually returned to the classical food chain. DOM includes three categories according to biological availability: labile DOM (LDOM; ~26 Gt C), semi-labile DOM (SLDOM; ~50 Gt C) and recalcitrant DOM (RDOM; ~624 Gt C). All percentage values represent the flux of C fixed by primary producers (100%).