itsIn ecology, carrying capacity means the maximum population size of a species that can be sustained by an environment given the available resources.
In a graphic that plots time vs population size, the moment the carrying capacity is reached can be identified easily by looking at which point the population stops growing and it just maintains its size.
Among the four species plotted here, species 4 is the one that reaches it's maximum first, around day 20, and after that just keeps the same population size.