Biological Action of Temperature 141 



situation over the ages has been that many oceanic plants and animals 

 have become adapted to a relatively stable temperature. 



The disadvantage of this easy life in the water is that when an un- 

 usual change in temperature occurs dire results may follow. Many 

 instances are known in which slight temperature changes have caused 

 mass mortality in the aquatic environment. A spectacular example 

 occurred in 1925 off the coast of Peru (Murphy, 1926). In the spring 

 of that year the cool Humboldt Current, which flows northward along 

 the coast, apparently moved slightly offshore, allowing the warm 

 countercurrent, El Niilo, to flow farther south than usual, raising the 

 temperature 5 or 6°C above normal. The result was that the plankton 

 and a great many of the local fishes were kflled. Larger fishes, de- 

 pendent upon these smaller forms of life for food, soon afterward 

 succumbed and washed up on the shore in windrows. In addition 

 huge numbers of fish-eating birds died of starvation. Many of these 

 birds inhabited coastal islands where their droppings produced guano 

 deposits of extreme value as fertilizer. Guano production was 

 stopped, and the coast line for miles was strewn with the carcasses of 

 the dead birds. Torrential rains caused by the slight change in ocean 

 temperature washed away tons of guano that had required generations 

 to accumulate. The heavy rainfall also devastated the neighboring 

 ordinarily arid land areas, disrupting the natural fauna and flora, and 

 destroying crops, roads, and buildings. The ecological and economic 

 repercussions of the oceanic change thus extended to the shore and 

 inland. A few months later the ocean currents returned to their nor- 

 mal course, and after a period of years the fauna and flora were grad- 

 ually restored. This cataclysmic destruction of ocean life off Peru 

 well illustrates the far-reaching consequences of a slight temperature 

 change in a situation where the plants and animals have become ad- 

 justed to relatively uniform conditions. 



BIOLOGICAL ACTION OF TEMPERATURE 



What are the ecological consequences on land and in the water of 

 the thermal conditions that have just been reviewed? Environmental 

 temperature exerts a direct action on the tissues of poikilothermous 

 organisms, that is, on those whose body temperatures vary with the 

 surroundings. The heat exchanges of homoiothermous animals are 

 also affected by external thermal conditions, but the insides of these 

 animals are thermostatically maintained at a nearly constant, and 

 relatively high, temperature. 



