Diel vertical migration of zooplankton in a hypertrophic shallow temperate lake, Germany

Abstract

ABSTRACT:Zooplankton as important links in the food web of aquatic ecosystems have been studied extensively. In current literature their diel vertical migration (DVM) is a highly discussed issue. In this investigation DVM by zooplankton is studied in a hypertrophic shallow lake in Germany. The objectives of the study were to see if DVM by zooplankton occurs in shallow lakes such as Lake Dagowsee, the possible overlap in DVM of Leptodora kindtii, an invertebrate predator, and zoopankton, and the effect of wind action on DVM. It was found out that DVM of zooplankton occurs in Lake Dagowsee despite the limited range of depth for migration, wind action can influence DVM and L. kindtii poses a complex situation in relation to DVM behaviour of zooplankton in Lake Dagowsee. Finally, further studies are suggested with regard to DVM variation between different species, size and hybrid groups of Daphnids, and identification of the light sensitive range that can cue DVM of zooplankton and L. kindtii in temperate and tropical waters.

Observations on the relations of some physico-chemical features and DVM of Paradiaptomus africanus in Lakes Bishoftu-Guda and Hora-Arsedi, Bishoftu, Ethiopia

“…Such a scenario is unimaginable in temperate lakes where summer stratification can only occur with 15 1C or more water temperature differences between the epilimnion and the hypolimnion (e.g. Lemma, 2004).…”

“…This phenomenon creates ecological gap where the less competitive and small sized zooplankton, mostly the rotifers, dominate in these two lakes (Lemma et al, 2001). P. africanus is known to overcome such pressures of vertebrates mainly due to their fast reaction and rapid movements (Masson et al, 2001;Lemma, 2004). From this study it was inferred that adaptation to migration by P. africanus into deeper waters by daylight and approaching surface waters in the dark was prevalent.…”

“…A considerable amount of both field and experimental evidences have accumulated to support this phenomenon as described by the generally accepted predator-evasion hypothesis (Stich and Lampert, 1981;Gliwicz, 1986;Hays et al, 1994). It is also argued that there are other cues that trigger the same behavior in zooplankton such as ultraviolet radiation (UVR) (Alonso et al, 2004), temperature (Ramos-Jiliberto and Zun˜iga, 2001), oxygen limitation (Besiktepe, 2001;De Robertis, 2002), availability and competition for food (Pearre, 2000), wind action (Lemma, 2004), prey size (Hays et al, 1994;Cuker and Watson, 2002), conductivity (Roman et al, 2001) and others. Further readings dealing with different aspects of the causes of dial vertical migration (DVM) can be made in such publications as Perticarrari et al (2004); Shimode and Shirayama (2004); Aguilera et al (2006); Nomura (2006); Tsui (2006); Blachowiak-Samolyk et al (2006).…”

“…Identification, counting and length measurements of the calanoids from among the assemblages of zooplankton were made from at least three homogenized 10 mL sub-samples in a sedimentation chamber under inverted microscope (Kasprzak et al, 1993). Mean body length of P. africanus of 30-40 individuals from each sample was used to calculate bio-volume of the animals from simple geometric models as a measure of biomass (Børshiem and Andersen, 1987;Lemma, 2004).…”

“…One such studied group of zooplankton are the copepods, particularly the largesized ones, the calanoids. There is a considerable amount of literature on this sector of the zooplankton that are known to have quite speedy reaction to changes in cues (Masson et al, 2001;Lemma, 2004) and in detecting the behavior of predators that have co-evolved with them (O'Brien, 1987). It is then generally accepted that zooplankton stay in the cold dark deeper water column during the day to ultimately avoid visual predation mostly by planktivorous fishes and migrate towards the warm food-rich surface water at night using nightfall as their refuge (McLaren, 1974;Zaret and Suffern, 1976;Stich and Lampert, 1981;Dagg et al, 1989).…”