12 



THE BIOLOGY OF MARINE ANIMALS 



TABLE 1.2 



A Partial List of the Minor Elements in Sea Water 

 (Chlorinity 19°/oo) 



(From various sources) 



nitrogen-containing salts are essential nutrient substances for the growth 

 of marine plants. An evaluation of this subject, which is outside the scope of 

 the present work, is available elsewhere (26, 27). Phosphorus is an essential 

 element in the composition of animals, and as inorganic and organic 

 phosphates it occurs in the skeleton, body and cellular fluids. Iron, copper 

 and vanadium are found in blood pigments, and iron is also an essential 

 element in certain intracellular enzymes; silicon is utilized in the coverings 

 and skeletons of diatoms, radiolarians, sponges, etc. 



Organic Matter. Sea water contains a small quantity of dissolved and 

 suspended organic matter, which is derived from the excreta of living 

 organisms and from the decomposition of their tissues when dead. The 

 amounts present are very small, and have been estimated at 1-2-2 mg of 

 carbon per litre. There appears to be more organic matter in inshore than 

 offshore waters, and some decrease during the winter months. A part of 

 the organic matter in solution is utilized by bacteria, but it does not appear 

 to contribute directly to the nourishment of marine animals (25, 37). On 

 the other hand, the presence of minute quantities of organic substances in 

 solution may well exert physiological effects out of all proportion to their 

 concentration. It has been demonstrated that the development of certain 

 echinoderm and polychaete larvae shows differing degrees of success in 

 samples of sea water from different localities, owing to the presence of 

 unknown factors. Studies of this kind may point the way towards deter- 

 mining the more elusive biological differences which exist between different 

 waters (42). 



Hydrogen Ion Concentration (pH). Sea water is normally alkaline in 



