MICROSCOPIC FAUNA OF SANDY BEACHES 



lUl 



Lecave hnlla, TricJioccrca nudficrinis, 

 Sccrrifliuni loncjicauihiyn, CcplialodcUd for- 

 ficiila, ciiid CcpJialodcIla eva. 



Thirty-nine species are known to be con- 

 fined almost exclusi^'ely to the sand environ- 

 ment. Some which were abundant in the 

 Wisconsin beaches are: Dicranopliorus licr- 

 ciilcs, Euchlanis arciiom, Lecanc inqiiicta, 

 Lecane paraclosterocerca, Trichocerca inso- 

 lens, and Wierzejskiella velox. 



Of the psammophile forms the following 

 were abnndant: CepJialodella gihha, Lecane 



an average of only al)ont one individual per 

 sample was fonnd. Althonp-h the relative 

 distribution of the rotifers in tlie sand was 

 fairly uniform it was found that the num- 

 bers in a single beach may vary as much 

 as fiftyfold over a period of lime. There 

 is great need for the causes of these varia- 

 tions to be worked out. 



The horizontal distribution was (juite 

 characteristic, but there were certain inter- 

 esting diversities. The mean distribution of 

 rotifers for four series of sand samples col- 



total 



Fig. 



100 150 200 250 300 



Dlatanea from water's adga, am. 



Mean horizontal distiilnition of Rotatoria to a dei)tli of 8 cm for four scries of 10 cc sand samples 



collected at a beach on the south shore of Trout Lake, Vilas County, Wisconsin. 



closterocerca, Lecane liamata, Lecane lun- 

 aris, Lecane scuiata. Lepadella patella, 

 Trichocerca intermedia, and Trichocerca 

 tenuior. 



Table III shows the populations of Rota- 

 toria in three typical series of samples. The 

 greatest population encountered during the 

 course of this study was found in the top cm 

 of sand lUU cm from the edge of the water 

 at a beach on Trout Lake on July 19, 1936. 

 This 10 cc sand sample contained more than 

 11,000 specimens. The smallest population 

 occurred in a beach on Lake Superior where 



lected at a beach on the south shore of 

 Trout Lake to a depth of 8 cm is shown in 

 Fig. 5. This beach was characterized by a 

 small i)roportion of psannnobiotic rotifers, 

 witli maxima of about 11 and 15 at the and 

 250 cm stations, respectively, while more 

 than 30 psammophile specimens per sam- 

 ple were found betAveen the edge of the 

 Avater and the 200 cm station. At the 300 

 cm station the total number of rotifers w^as 

 only about two per sample. 



In contrast, the mean values for a beach 

 on the northeast shore of Muskellunge Lake 



