The role of macrophytes in the diurnal distribution of crustacean zooplankton in a littoral of a shallow, macrophyte-dominated lake

In a mesotrophic, shallow, macrophyte-dominated lake, stable plant cover can be attractive for zooplankton species being a grazer or a prey; dense submerged vegetation, Chara beds in particular, can offer a day-time refuge for cladocerans and some adult copepods. The former use this shelter also at night; on the contrary, young stages of Copepoda distinctively avoided both types of plant covered areas during the day and migrated towards open water. That might resulted from the increased grazing upon zooplankton. The pressure of predatory fish in open water probably forced young fish to seek for a shelter. As Chara beds are too dense to be penetrated, they preferred emergent plant zone. That might encourage copepods to undertake reversed DHM. The present study suggests a significant role of plant cover on diurnal zooplankton distribution. Dense charophyte patches could offer a daytime refuge for cladocerans, and some adult forms of Copepoda, while both groups of planktonic invertebrates did not take the advantage of emergent macrophytes cover to avoid fish predation.