STUDIES IN MARINE ECOLOGY. 



237 



found within a given association? The available data on these 

 points for the months of August and early September, will be 

 presented by tables for the two series studied. 



a. Rocky Eroding Shores. — The average conditions in the 

 eroding shore series when conditions are most acute, are shown 

 in Table XIV. This series is composed of the associations of 



Table XIV. 



Eroding Shore Series. 



Showing average salinity, oxygen content, temperature, and pH of different 

 animal associations as found in collections from the bottom at low tide except for 

 salinity where low and mid-tide data are averaged. The last two associations are 

 added for comparative purposes. 



Ordinal ranking is based upon variation from conditions known to occur in 

 open water. 



Association. 



Salinity. 



O2 c.c. per L. 



Temperature 



pH. 



Open 



Wharf pilings . 

 Exposed rocks 

 Rockweed. . . 



My a 



Melampus . . . 



5-17, I 



4-72, 2 



5-9i[ 3 



6.33 4 



21. 1 2 



20.0 1 



2I.4J 3 



21.51 4 



8.0 

 8.0 

 8.16 

 8.13 



5-5 

 6-5 

 13 



IS 



23 



the open water, wharf pilings, exposed rocks, and rockweeds 

 growing on protected rocks. Data from the intertidal associa- 

 tions at the back of mud flats are added for comparisons. 



The average salinity at low and mid-tides decrease in the 

 order given. The average low tide temperatures increase in the 

 order given from the wharf pilings but these, contrary to expecta- 

 tion, are lower than the open water. The average oxygen tension 

 varies from that found in the open water by amounts which 

 likewise arrange the series in the order given. Thus the wharf 

 pilings gave an average of 4.72 c.c. of oxygen per liter which is 

 0.49 less than the average found in open water; while the exposed 

 rock association with an observed average of 5.1 c.c. per liter is 

 0.74 c.c. from the open water conditions. 



1 Must range from almost fresh water during rain at low tide to about 3.00 at 

 high tide. 

 16 



