IV-81 



temperature and salinity. The rate of Input of solar radiation is 

 greater 1n the tropics than 1n the arctic, and life in tropical en- 

 vironments 1s more prolific than 1n the arctic. 



Although water temperatures in the estuarine zone are closely related 

 to the input of solar radiation, they are also greatly influenced by 

 the temperatures of nearby cold or warm ocean currents. Many plant 

 and animal species tolerate a wide enough temperature range to survive 

 in considerable stretches of the estuarine zone from north to south. 



There are a considerable number of plants and animals that have adapted 

 to temperature ranges in the colder estuarine zone; others have adapted 

 to temperature ranges occurring 1n the warmer temperate and sub-trop1c 

 waters of the estuarine zone; and there are some that have adpated to 

 the colder waters of the northern estuaries, the warmer waters of the 

 southern estuarine zone, and the gradations 1n between. Figure 

 IV. 1.37 shows the temperature ranges tolerated by some characteristic 

 estuarine organisms. 



The quality of water 1n the estuarine zone has sometimes dramatic, 

 sometimes subtle, effects on estuarine life. The dissolved and par- 

 ticulate nutrients so plentiful in the coastal zone make this area 

 very productive compared to other parts of man's environment. The 

 coral reef communities of the tropics, where energy conversion is 

 primarily a matter of photosynthesis, are nowhere near as productive 

 as the oyster reefs and marshlands of the temperate zone, where par- 

 ticulate organic foods as well as solar energy are converted into plant 

 and animal tissue for use by animals higher in the food chain. 



