MICROSCOPIC FAUNA OF SANDY BEACHES 



105 



Fig. 8. Horizontal distiibution of maximum numbers of copepods in 14 different series of sand samples. 

 Asterisks indicate points on surface of sand which Avere 12 em above lake level. 



siderable numbers of Copepoda were also 

 found in the deep samples at beaches ex- 

 posed to frequent and vigorous wave action. 

 In several instances these organisms were 

 found as deep as 11 em. 



OTHER ORGANISMS 



Insect larvae, particularly Diptera, were 

 found distributed at random in the beaches. 

 Although a few were as deep as 7 cm, most 

 were in the upper 4 cm. They were numer- 

 ous in beaches containing large quantities 

 of organic material and in several instances 

 numbered more than two individuals per 

 10 cc of sand. 



Gastrotricha were present in most of the 

 samples taken within 150 cm of the lake 



where the sand was (juite wet. Some 

 samples contained more than 100 individu- 

 als, but in most cases there were compara- 

 tively few. 



Nematodes were abundant in the outer 

 regions of beaches. Some series of samples 

 had mean populations of more than 2 per 

 10 ce of sand. 



Turbellaria of the genus DalyeJUa were 

 numerous in certain beaches, up to 15 per 

 sample. The majority by far were found 

 within 150 cm of tlie shoreline. 



Many species of algae inhabit the sand ; 

 the main groups are the Cyanophyceae, 

 Chlorophyceae, and Bacillariae of the gen- 

 era commonly found in the plankton. On 

 the shores of soft-water lakes desmids were 



TABLE VI 



Mean Vertical Distribution of Copepoda to a Depth of Eight cm in Seven Different 

 Beache-s. Mean Numbers of Specimens Per 10 cc Sand Sample. 



