14 



THE BIOLOGY OF MARINE ANIMALS 



TABLE 1.3 



Solubility of Oxygen in Sea Water (ml/1.) 

 (From Fox (21)) 



combination with the excess base, which allows sea water to hold larger 

 amounts of C0 2 than distilled water at the same partial pressure. 



Laboratory Sea Water 



The sea water which is used in the aquaria of marine laboratories often 

 differs substantially from natural sea water for various reasons. Different 

 laboratories have their own methods of maintaining a sea-water circulation. 

 The majority use sea water pumped from the sea and circulated in a closed 

 system for variable periods. This, of course, is subject to evaporation and 

 liable to concentration. Owing to the death and decomposition of animals, 

 especially in warm weather, there may be an increase in the amount of 

 organic matter in circulation. Oxygen levels in tanks may fall well below 

 saturation, depending on total respiratory exchanges of aquarium animals. 

 The hydrogen ion concentration tends to rise owing to the absence of 

 plants, and some laboratories raise the pH by liming, or by the addition 

 of sodium bicarbonate. In the Plymouth Laboratory, for example, water 

 of salinity 38% and pH 7-9 had a calcium content of 0-62 g 1., compared 



