....... capacity is the largest numbers of individuals of one species that an ecosystem can support over time.

What kind of capacity???

http://www.scienceray.com/Biology/Ecology/Population-Limits-in-an-Ecosystem.159603

individuals in a population

The capacity referred to in this context is called the ecological carrying capacity or simply the carrying capacity of an ecosystem. It is the maximum number of individuals of a species that can be sustained by the resources and environmental conditions within the ecosystem over an extended period of time. This capacity is determined by the available resources such as food, water, shelter, and other factors like predation, competition, and disease. It is important because it sets a limit on the population size that an ecosystem can support without causing detrimental impacts such as resource depletion or environmental degradation. To determine the carrying capacity of an ecosystem, several scientific methods and models can be used, including population surveys, mathematical modeling, and statistical analysis. These approaches help scientists estimate the maximum sustainable population size for a particular species in a given area.