Reichwaldt Elke S, Stibor Herwig
Department Biologie II, Aquatische Okologie, Ludwig-Maximilians Universität München, Grosshadener Str. 2, 82152, Martinsried, Germany.
Oecologia. 2005 Nov;146(1):50-6. doi: 10.1007/s00442-005-0176-3. Epub 2005 Oct 22.
Diel vertical migration (DVM) of large zooplankton is a very common phenomenon in the pelagic zone of lakes and oceans. Although the underlying mechanisms of DVM are well understood, we lack experimental studies on the consequences of this behaviour for the zooplankton's food resource-the phytoplankton. As large zooplankton species or individuals migrate downwards into lower and darker water strata by day and upwards into surface layers by night, a huge amount of herbivorous biomass moves through the water column twice a day. This migration must have profound consequences for the phytoplankton. It is generally assumed that migration supports an enhanced phytoplankton biomass and a change in the composition of the phytoplankton community towards smaller, edible algae in the epilimnion of a lake. We tested this assumption for the first time in field experiments by comparing phytoplankton biomass and community assemblage in mesocosms with and without artificially migrating natural stocks of Daphnia hyalina. We show that DVM can enhance phytoplankton biomass in the epilimnion and that it has a strong impact on the composition of a phytoplankton community leading to an advantage for small, edible algae. Our results support the idea that DVM of Daphnia can have strong effects on phytoplankton dynamics in a lake.
大型浮游动物的昼夜垂直迁移（DVM）是湖泊和海洋中上层水域非常普遍的现象。尽管DVM的潜在机制已得到充分理解，但我们仍缺乏关于这种行为对浮游动物食物资源——浮游植物——影响的实验研究。由于大型浮游动物物种或个体白天向下迁移到较深、较暗的水层，夜间向上迁移到表层，大量的食草生物量每天在水柱中移动两次。这种迁移必定会对浮游植物产生深远影响。一般认为，迁移会增加浮游植物的生物量，并使浮游植物群落组成朝着湖泊上层较小型、可食用藻类的方向变化。我们首次通过比较有和没有人工迁移透明溞自然种群的中型生态系统中的浮游植物生物量和群落组合，在野外实验中检验了这一假设。我们发现，DVM可以增加湖泊上层的浮游植物生物量，并且对浮游植物群落组成有强烈影响，从而使小型、可食用藻类占优势。我们的结果支持了这样一种观点，即溞的DVM会对湖泊中的浮游植物动态产生强烈影响。
