Hydrogen Ion Concentration and Other Factors 

 Affecting the Distribution of Fucus 



Floyd W. Gail 

 University of Washington, Seattle 



Introduction 



During the summer of 1918 the writer worked on the effect of light 

 and desiccation on the distribution of Fucus evanescens Agardh. In 

 places, however, little or no Fucus was found where there was sufficient 

 light and where desiccation to any considerable extent did not occur. 

 Fucus frequently did not occur in bays which had light as well as suitable 

 places for attachment. The writer has never found growing Fucus in 

 tide-pools, although some were completely surrounded by it. Fucus does 

 not grow where Ulva is found in any considerable quantity. Both Fucus 

 and Ulva utilize the CO, in the sea-water during the day in the synthesis 

 of their carbohydrates, thus causing the water to become more alkaline. 

 During the night CO2 is given off, thus causing the water to become more 

 acid. Animals also add to the acidity of the water. Tests showed the 

 hydrogen ion. concentration to be much higher where Ulva grew than 

 where Fucus grew. 



Historical 



Little work has been done on the factors causing the distribution of 

 Fucus. Davis (1911) says the depth to which certain algae may descend 

 depends upon the penetration of light. The factor that determines the 

 lowest limits of algal life is not the depth of the water but the absence of 

 light. The green algae require the most light, the red the least and the 

 browns are intermediate. The same writer also considers that the influence 

 of temperature must be of fundamental importance in the distribution of 

 algae where the seasonal extremes are as great as those of the summer and 

 vv'inter at Woods Hole. There Fucus is found in its best vegetative con- 

 dition during winter and spring, fruiting most abundantly during the 

 latter season. It is represented during the summer by dwarfish growths, 

 frequently lighter in color than tlie winter condition in which the growth 

 and fruiting is more uniform. Most of the winter growth matures during 

 the spring, hence tlie display of Fucus during the summer is comparatively 

 poor. 



Gail (1918) found that light and desiccation are controlling factors in 

 the distribution of Fucus. 



(287) 



