De-acclimation

De-acclimation refers to the process by which an organism loses its acclimatization, or its physiological and behavioral adaptations, to a specific environmental condition. This typically occurs when the organism is removed from that environment or when the environmental conditions change, returning closer to a state of unadaptedness. It is essentially the reversal of acclimatization and can manifest as a decline in tolerance to the formerly adapted conditions, leading to reduced performance, increased susceptibility to stress, and potentially even mortality. The speed and extent of de-acclimation vary depending on the organism, the degree of initial acclimatization, and the nature of the environmental change. It is a crucial concept in understanding how organisms respond to dynamic environments and the impacts of environmental change.

De-acclimation meaning with examples

• A hiker, long accustomed to high altitude, returns to sea level. Their body, having adapted to the reduced oxygen levels at altitude (acclimatization), will start the process of de-acclimation. Symptoms may include increased susceptibility to the effects of alcohol, decreased cardiovascular capacity during intense activity and a feeling of being sluggish due to the increased oxygen levels. These changes reflect a loss of altitude acclimatization and a re-adjustment to the lower-altitude environment.
• Tropical fish, having acclimated to the consistent warmth of a heated aquarium, are placed in an unheated tank. The sudden drop in water temperature triggers de-acclimation. The fish's metabolic rate slows, their immune systems become weakened, and they struggle to regulate their internal body temperature (poikilothermy), which increases the risk of disease or death. This demonstrates the biological costs of losing prior environmental adaptations.
• A plant, which acclimated to a drought by adjusting its stomata for water retention, is then placed in consistently watered soil. The plant starts a process of de-acclimation, reversing its drought tolerance mechanisms. Its leaves may begin to transpire more freely, and water uptake through the roots might not be at the optimal rates of the current environment. Eventually, the plant returns closer to its original growth strategy or adapts to its new environment.
• Athletes who have trained in a hot and humid environment for an extended time develop physiological adaptations like increased sweat rates to better regulate their body temperatures (acclimatization). When they transition to a cooler and drier environment, they begin de-acclimation, decreasing the efficiency of their sweating response. This can increase their susceptibility to heat-related illness during their competitions until they reacclimatize to the new conditions.