An in situ method for the investigation of vertical distributions of zooplankton in lakes: test of a two-compartment enclosure

Abstract

Two-section enclosures were designed for the investigation of the effect of various physicochemical and biological factors on vertical distribution of zooplankton in situ. The framework of the enclosure was a cylindrical polyethylene column without any partitions inside, in which the isolation of animals in different sections after in situ exposure was achieved by pinching the flexible central part of the column. Enclosures were tested at the brackish stratified meromictic Lake Shira (Russia, Khakasia). The absence of fish and carnivorous zooplankton in the lake suggests that the vertical distribution of zooplankton is mainly determined by physicochemical gradients in the water column. Experiments and field observations demonstrated that all age and size groups of Arctodiaptomus salinus and Brachionus plicatilis strongly avoided surface layers during the daylight. The escape of zooplankton from the anoxic hypolimnion was less active. Statistically significant avoidance was observed only for copepodites C4-C5 and females of A. salinus. The relatively simple construction of the columns and easy handling during the experiment were the factors that favoured the use of this device to perform in situ basic tests of the effect of different factors on the vertical distribution of zooplankton.

Summer depth selection in crustacean zooplankton in nutrient‐poor boreal lakes is affected by recent residential development

“…Thermal stratification and associated physicochemical gradients have been shown to influence patterns of depth selection and vertical distribution of crustacean zooplankton in stratified lakes (Winder, Buergi & Spaak, 2003; Thackeray et al. , 2006; Johnson, O’Brien & MacIntyre, 2007) and enclosure experiments (Tolomeyev & Zadereev, 2005). In deep lakes, stratification exposes zooplankton to sharp vertical gradients in light, temperature, oxygen, food concentrations and predation risk.…”

“…In lake ecosystems, habitat complexity arises as the result of vertical and horizontal structuring of freshwater habitats and is reflected in the distribution patterns of zooplankton (Pinel-Alloul, 1995;Pinel-Alloul & Ghadouani, 2007). Thermal stratification and associated physicochemical gradients have been shown to influence patterns of depth selection and vertical distribution of crustacean zooplankton in stratified lakes (Winder, Buergi & Spaak, 2003;Thackeray et al, 2006;Johnson, O'Brien & MacIntyre, 2007) and enclosure experiments (Tolomeyev & Zadereev, 2005). In deep lakes, stratification exposes zooplankton to sharp vertical gradients in light, temperature, oxygen, food concentrations and predation risk.…”

Feeding spectra of Arctodiaptomus salinus (Calanoida, Copepoda) using fatty acid trophic markers in seston food in two salt lakes in South Siberia (Khakasia, Russia)

“…Thus, the epilimnion population of A. salinus must migrate to these deeper waters to maintain in their bodies the observed levels of these acids. This argument, however, is not supported by Tolomeyev and Zadereev (2005) who found that diel vertical migration of A. salinus in Lake Shira is weakly pronounced due to the absence of predators for zooplankton. Nevertheless, the difference between day and nighttime distribution profiles of A. salinus does comprise its lower day-time density in the upper (1 m) layer probably due to a negative phototactic response to intensive solar radiation.…”