Members Platform
MSc Research on "The effects of Daphnia diel vertical migration on phytoplankton dynamics and their implication for Daphnia life history parameters in the pelagial of lakes."
In my MSc Research, I had the fantastic opportunity to work with PD Dr. Herwig Stibor, Dr. Elke Reichwaldt and Prof. Dr. Sebastian Diehl from the Aquatic Ecology Group at Ludwigs-Maximilans University in Munich. This group closely collaborated with the Max-Planck Research Institute for Limnology in Ploen.
Two papers were published from this research:
Reichwaldt, E.S., Wolf, I.D. & Stibor, H., (2005). Effects of a fluctuating temperature regime experienced by Daphnia during diel vertical migration on Daphnia life history parameters. Hydrobiologia 543, 199–205.
Abstract
Many freshwater zooplankton species perform a diel vertical migration (DVM) and spend the day within the lower, colder hypolimnion of stratified lakes. Trade-offs that arise from this migration have already attracted much attention and the cold temperature in the hypolimnion is thought to be the main cost of this behaviour. In this study we additionally looked at the extra costs daphnids have from being exposed to a fluctuating temperature regime (cold during the day and warm during the night) which is less well studied until today. In our experiment Daphnia hyalina Leydig and Daphnia magna Straus either spent 24 h in constant warm water (19 °C), 24 h in constant cold water (12 °C), or spent 12 h in warm and 12 h in cold water in an alternating way (fluctuating temperature regime). We expected the values of the life history parameters of Daphnia in the fluctuating temperature regime to be exactly halfway between the values of the life history parameters in the warm and cold treatments because the daphnids spent exactly half of the time in warm water, and half of the time in cold water. Concordant with earlier studies our results showed that age at first reproduction and egg development time were reduced at higher temperatures. In the fluctuating temperature regime the values of both parameters were exactly halfway between the values at permanently warm and cold temperature regimes. In contrast, somatic growth was higher at higher temperatures but was lower in the fluctuating temperature regime than expected from the mean somatic growth rate. This suggests that a fluctuating temperature regime experienced by migrating daphnids in stratified lakes involves additional costs for the daphnids.
Reichwaldt, E.S., Wolf, I.D. & Stibor, H., (2004). The effect of different zooplankton grazing patterns resulting from diel vertical migration on phytoplankton growth and composition: a laboratory experiment. Oecologia 141, 411–419.
Abstract
Diel vertical migration (DVM) of herbivorous zooplankton is a widespread behavioural phenomenon in freshwater ecosystems. So far only little attention has been paid to the impact of DVM on the phytoplankton community in the epilimnion. Some theoretical models predict that algal population growth in the epilimnion should depend on the herbivores
migration and grazing patterns: even if migrating zooplankton consume the same total amount of algae per day in the epilimnion as non-migrating zooplankton, nocturnal grazing should result in enhanced algal growth and favour algal species with high intrinsic growth rates over species with lower intrinsic growth rates. To test these hypotheses we performed experiments in which several algal species were confronted with different feeding regimes of Daphnia. In the experiments algal growth did not only depend on the absolute time of grazing but was comparatively higher when grazing took place only during the night, even when the grazing pressure was the same. Furthermore, algal species with higher intrinsic growth rates had higher advantages when being grazed upon only discontinuously during the night than algal species with a smaller intrinsic growth rate. The grazing pattern itself was an important factor for relative algal performance.