In many resort towns, the influent loads to the wastewater treatment system are highly variable throughout the year. During the tourist seasons there is an abundance of wastewater to sustain the biomass at treatment facilities, but when the transient population leaves, there is a drastic reduction in organic substrate. The organic carbon supplied to the system, the carbonaceous biological oxygen demand (CBOD), serves as a food source for organotrophic organisms in activated sludge systems. The ratio of food to microorganisms (F:M) in wastewater declines correspondingly with CBOD. Low levels of organic substrate slow cellular growth which indicates a biomass is using emergency carbon stores to fuel cellular function.