Diurnal vertical migration of some cladocerans in relation to the physico-chemical factors in a fish pond

Abstract

Diurnal vertical migration of four genera of cladocerans, namely Diaphanosoma sp., Daphnia sp., Moina sp. and Bosmina sp., during March to December, 2007 showed that the number of Diaphanosoma sp. was 501 units/1 in the surface layers, 172 units/l in the middle layers and 190 units/l in the bottom layers. The yearly number of Daphnia sp. in surface, middle and bottom layerss was 362 units/l, 46 units/l and 189 units/l respectively. In surface, bottom and middle layers, the number of Moina sp. was 159, 71 and 32 uiiits/l, respectively. Bosmina sp. was 78 units/l in surface, 31 units/l in the middle and 33 units/l in the bottom layers. The number of Diaphanosoma sp., Daphnia sp., Moina sp., Bosmina sp., were 455, 149, 259 and 358 units/l, respectively in the morning, 63, 176, 142, 43 units/l at noon and 107, 55, 28, 59 units/l, respectively in the evening. Throughout the study period the cladocerans were always abundant near the surface during morning and evening. Among the factors responsible for the diurnal movement of cadoceran, light played the most important factor. The relationship between the physico-chemical factors and the cladoceran occurrence in the pond was also explored.

A review of potential methods for zooplankton control in wastewater treatment High Rate Algal Ponds and algal production raceways

“…Zooplankton, especially cladocerans, commonly undertake diurnal vertical and horizontal migrations through the water column [122]. Migration is typically in response to changes in temperature, DO, pH, carbonate and bicarbonate ions, photosynthetic activity, predators and light, the latter of which is considered the most important, both for avoidance of visual predators and UV radiation [123][124][125]. Zooplankton often move to the warmer, food-rich surface layer after sunset and then move back into deeper water before sunrise to avoid visual predators [126,127].…”

Optimal production of microalgae in the presence of grazers

“…The first one is that zooplankton often escape the outflow of the pond. For example, cladocerans migrate to near the pond surface at night, resulting in lower densities in the deep water column where the outflow is often located [6,16]. This has also been observed in chemostat experiments, where cladocerans concentrate near the bottom of the chemostat, remaining below the surface from which the overflow occurs [17].…”