Biotic factors are living organisms affecting a particular ecosystem and their relationships. Fish, frogs, water plants, bacteria and insects are biotic factors in a river habitat.
Indirect measurements of biotic factors establish valuable information about an environment and its inhabitants. A high concentration of chlorophyll a in an estuary is an indicator of algal bloom; a dangerous spike in the number of algae that can lead to die-offs of estuary inhabitants. A drop in biodiversity flags the decreased health of an ecosystem.
Abiotic factors are nonliving impacts on an ecosystem and include weather, landforms, water salinity and geologic events. Measurements of soil density, water availability and hours of sunlight indicate the likelihood of plant survival and of the survival of animals dependent on that plant as a food source. Dryer weather patterns shift the composition of a habitat to drought-friendly species.
Biotic and abiotic factor studies have commercial impacts. The Formosa subterranean termite causes up to $2 billion damage per year in the United States. Identifying a particular landform's value to the termites allows focused prevention measures at its location. Methylmercury contamination from a coal plant accumulates in fish tissues and not only causes damage to the sports fishing industry but requires new protocols for unsafe food consumption warnings.