A study in the tolerance of various Cladocera to oxygen deficiency in the water

Abstract

The importance of oxygen deficiency in the water as a factor limiting the distribution of Cladocera has been investigated. A method has been devised by means of which Cladocera can be subjected to a constant degree of oxygen lack for any desired time. A comparison was made between the ability of pond and lake dwelling Cladocera to survive under conditions of oxygen deficiency. The results obtained indicate that Cladocera living in the open waters of large lakes die rapidly when placed in waters of low oxygen content, in which pond dwelling species can survive for many hours. Animals living in small ponds experience a diurnal fluctation in the amount of dissolved oxygen in the water. In some ponds the amount of dissolved oxygen frequently falls to very low levels at which planktonic lake dwelling Cladocera are incapable of survival for 4 hrs. This may account for the absence of planktonic species from small ponds.