Experiments with Marine Algae in Fresh Water 



Lola B. Brown, 

 University of Kansas, Lawrence. 



Among the factors affecting marine algae are heat, light, dissolved 

 gases, evaporation, beating of waves or currents of water, the chemical 

 composition of rocks to which they are attached and the saltiness of the 

 water. The last factor, the relation of some marine algae to saltiness of 

 water, was chosen for experimentation. 



All parts of the sea are not equally salty, so it may be assumed 

 that algae do not all need the same amount of salt. Algae growing near 

 the mouths of rivers must of course be exposed to much less salt than 

 those growing in normal sea water ; and those growing in tide pools filled 

 by spray during a season when evaporation is rapid, must be exposed to 

 more salt than those in normal sea water ; especially is this true of tide 

 pools which are above the high-water line and often have salt crystals in 

 them. 



Osterhout^ found that Enteromorpha hopkirkii would grow in dis- 

 tilled water for a month ; and his observations on seaweeds growing on 

 vessels plying between fresh and salt water- would indicate that many 

 seaweeds would grow for a time in fresh water without injury. 



It was observed that Enteromorpha intestinalis grows where fresh 

 water seeps into sheltered tide pools, so it was chosen as a plant that 

 could probably live in weak salt solutions, though it is never found grow- 

 ing in fresh water. 



To find out the relation of Entermorpha to fresh water, a series 

 of fourteen pails was placed in a fairly cool sheltered place where only 

 the morning sun could reach them. The pails contained four liters of 

 water each. The water was ordinary sea water diluted with the following 

 per cents of fresh water: 100, 98, 95, 90. 85, 80, 75, 70, 60, 50, -iO, 30, 

 20, and 10. No pail containing undiluted sea water was used, because it 

 seemed certain that Enteromorpha can live in that, and the experiment 

 was started with the single purpose of finding out if Enteromorpha can 

 thrive in fresh water. For that reason the finer gradations were made 

 near the fresh-water end of the series. Into these pails were placed stones 



iThe Role of Osmotic Pressure in Marine Plants. Univ. Calif. Pub. Bot., 

 2: 229-230. 1906. 



2The resistance of certain Marine Algae to change in Osmotic Pressure 

 and Temperature. Univ. Calif. Pub. Bot., 2: 227-228. 1906. 



(31) 



