MICROSCOPIC FAUNA OP SANDY BEACHES 



in 



biological conditions. In all cases, however, 

 there was significantly more free carbon 

 dioxide in the capillary water than in the 

 adjacent lake water. In determinations 

 made at 13 beaches the free carbon dioxide 

 in the sand at the edge of the water ranged 

 from 2.0 to 9.5 ppm, while at the 100 cm 

 stations the amonnt varied from 4.5 to 38.0 

 ppm. It is likely that the more frequent 

 wave action near the edge of the water dis- 

 courages bacterial action and the conse- 

 quent production of carbon dioxide. There 

 were greater quantities of free carbon di- 

 oxide in beaches protected from wave action 

 than in exposed beaches. 



Varying amounts of bound carbon di- 

 oxide were also found, even at different sta- 

 tions in the same beach. In general, how- 



ever, the capillary water contained more 

 than the lake water, sometimes as miicli as 

 50 per cent more. 



In nearly all cases the capillary water 

 was more acid than the adjacent lake water, 

 from .1 to 1.3 pH units. Undoubtedly the 

 hydrogen ion concentration is subject to 

 variations even during the course of a 

 single day, in spite of buffer mechanisms 

 presumably present in the sand. Tliese 

 variations are yet to be determined. 



As for dissolved organic and inorganic 

 materials, it was found that the majority 

 of beaches are environments appreciably 

 richer in these substances than the waters 

 of the lake. This is particularly true on 

 the shores of soft-water lakes. Much fun- 

 damental work can be done on the absorp- 



FiG. 3. Optical section of a small portion of a sandy beach showing relative sizes of sand grains and some 

 of the common species of microscopic Metazoa. 1 = rotifers, 2 = gastrotrichs, 3 = tardigrade, 4 - nematode, 



5 = harpacticoid copepods. 



