JOURNAL OF PLANKTON RESEARCH | VOLUME 13 | NUMBER 1 | PAGES 187-196 | 1991
© Oxford University Press
research-article |
In situ diel variation in gut pigment contents of Ceriodaphnia sp. in stratification and destratification periods
Departamento de Ecología, Facultad de Ciencias, Universidad de Málaga, Campus Universitario de Teatinos 29071-Málaga, Spain
Received on April 3, 1990; accepted on September 18, 1990 The short-term, in situ diel grazing of Ceriodaphnia sp. during periods of stratification and mixing was investigated using the technique of fluorimetric analysis of the gut pigments. There were considerable seasonal differences in feeding behaviour In mixing, when the concentration of chlorophyll a in the water column was high and Ceriodaphnia abundance was low, gut pigment contents showed clear diel variation patterns, probably due to diel variations of the high values of feeding activity observed in the 24 hour cycle The maximum values were found at dawn. On the other hand, no diel variations in gut pigment were observed during periods of stratification and while the amounts of pigments in the water and in the gut were very low, species abundance was high. Taking into account the ambient conditions, the authors discuss the possibility that the change of feeding of the Ceriodaphnia sp. observed when the environment changed from a mixing period to one of stratification represents a change from herbivorous to detritivorous behavior.