The Nature of Sea Water 35 
and work has been done by oceanographers in the correla- 
tion of the chemical properties of sea water and the abun- 
dance of certain forms of sea life, both as functions of locality 
and time.of year. Such studies have a commercial importance 
(for fishermen and oyster farmers ), as well as a purely scien- 
tific interest. 
LIVING CHEMICAL FACTORIES | 
Among the fascinating processes of nature is the way that 
living organisms are able to concentrate certain chemical 
elements within their bodies. An example is the way that the 
human organism concentrates iron in the blood hemoglobin. 
Marine organisms are very versatile in this respect, some con- 
centrating iron, calcium, silica, copper, boron, iodine, stron- 
tium, even arsenic! Some marine plants have a mysterious 
way of collecting iodine from the sea—as a matter of fact, 
seaweeds gathered on the shores and chemically treated are 
the commercial source of iodine. If the seaweeds did not per- 
form the preliminary task of separating the iodine from the 
sea water, we would have a very difficult task obtaining it 
ourselves. 
Similarly, calcium is concentrated by shellfish; phosphorus 
by brachiopods; silica by diatoms; strontium by some animals 
who seem to prefer it for their bones in place of calcium. 
Copper is apparently essential for the oyster; potassium for 
certain algae. Radioactive elements including radium—as 
rare as they are in sea water—are concentrated by sea ani- 
mals about 100 times. : 
The table of elements present in sea water which was 
given above does not contain reference to dissolved gases 
which may be present in it; but they may be present in con- 
