Physiology And Climate Change

摘要

Ongoing ecosystem changes in response to climate change include poleward or altitudinal shifts in geographical distribution (1-3), population collapses or local extinctions (4), failure of large-scale animal migrations (5), changes in the seasonal timing of biological events (6), and changes in food availability and food web structure. These changes are largely driven by environmental temperature (1, 7). Examples from aquatic animal communities show that study of physiological mechanisms can help to elucidate these ecosystem changes and to project future ecological trends. All organisms live within a limited range of body temperatures, due to optimized structural and kinetic coordination of molecular, cellular, and systemic processes. Functional constraints result at temperature extremes. Increasing complexity causes narrower thermal windows for whole-organism functions than for cells and molecules, and for animals and plants than for unicellular organisms (8). Direct effects of climatic warming can be understood through fatal decrements in an organism's performance in growth, reproduction, foraging, immune competence, behaviors and competitiveness. Performance in animals is supported by aerobic scope, the increase in oxygen consumption rate from resting to maximal (9). Performance falls below its optimum during cooling and warming. At both upper and lower pejus temperatures, performance decrements result as the limiting capacity for oxygen supply causes hypoxemia (4,8) (see the figure, left). Beyond low and high critical temperatures, only a passive, anaerobic existence is possible. Fish rarely exploit this anaerobic range, but invertebrates inhabiting the highly variable intertidal environment use metabolic depression, anaerobic energy production, and stress protection mechanisms to provide short- to medium-term tolerance of extreme temperatures.