Growth of Daphnia longispina L. in a polyhumic lake under various availabilities of algal, bacterial and detrital food

摘要: The availability and importance of food sources for growth Daphnia longispina L. from a highly coloured fishless lake with anoxic hypolimnion were assessed by combining in situ laboratory experiments. In experiments populations enclosed tubes natural temperature stratification or without hypolimnion. the source (littoral zone vs pelagic epilimnion) was enclosing moss thalli zooplankton population large-scale flow-through system supplying experimental Daphnia. Growth juveniles epilimnetic water determined batch culture increasing concentrations bacteria algae their development investigated small-scale system. Access to enhanced 23–24%. rates 0.36 0.16 d−1 July August respectively. anoxia corresponding values 0.29 0.13. batch-cultures highest rate overall lower than able grow darkness 10 days 0.16. fed littoral reproduced well despite low concentration increased its number factor c. 32 days. However, animals small net production thus under influence control treatment. Population could survive grew slowly on pelagial processed community very little left. It is possible that serve as ‘life-support system’ enabling survival over periods algal shortage. Small-scale revealed mature reproduce bacterial diet if high enough achieve similar those an diet. threshold level estimated be 18.5 μg C 1−1. Detrital material limited value nutrition even where more 75% carbon bound particulate detritus.