Biotic Stressors

Biotic stressors could be pathogenic, parasitic, or predatory in nature and originate from living organisms. Both pathogenic and parasitic stressors have effect on the health of the entity hosting the pathogen/parasite. This effect starts at a molecular level, with the host radiating into a whole ecosystem level - especially if the host is a keystone species. For most pathogens, there is a positive relationship between the dose (the quantity of pathogens) and the response (reaction from the host) such that the occurrence and severity of the stressor (effect of the pathogens) on the host are proportional to the number of pathogens to which a host organism is exposed to. The above relationship holds true for parasite-host relationship. The commonality between pathogen and parasite relationships with their host is that in both situations the response could be observed at molecular, cellular, organ, and whole-organism level. Predation in an ecosystem is somewhat similar to the above description except that the response starts at population (prey) level. The prey is the population that is receiving the effect of the stressor (predation) coming from the predators, which are also individuals within a population.

Biotic stressors could also be any of the introduced invasive or exotic species in an ecosystem such as African honeybee (Mellifera scutellata), Asian tiger mosquito (Aedes albopictus), or kudzu (Pueraria montana) on land. In freshwater systems, animal species such as bighead carp (Hypophthalmichthys nobilis), lionfish (Pterois volitans (Linnaeus)), or plants such as common water hyacinth (Eichhornia crassipes) can be considered biological stressors. An epidemic of army worm infestation on a corn field or locust infestation of epidemic proportion on vegetation could impose severe stress on other organisms. In fact, direct human disturbance such as harassment or overhar-vesting of wildlife or fishes could be considered biological stressors in nature.

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