From Wikipedia: Biomass, in ecology, is the mass of living biological organisms in a given area or ecosystem at a given time. Biomass can refer to species biomass, which is the mass of one or more species, or to community biomass, which is the mass of all species in the community. It can include microorganisms, plants or animals. Use in ECSO: There are many methods and usages of biomass measurements. This ECSO class is for a group of measurements where only the mass of the material was recorded. Pertinent area and datetime components are implicit (or in the protocol). The mass can be expressed as an average, or as the total mass in the community.