Mesocosm experiment on the impact of invertebrate predation on zooplankton of a tropical lake

Abstract

Invertebrate predation on zooplankton was investigated in mesocosms in the shallow tropical Lake Monte Alegre, São Paulo State, Brazil, in the summer of 1999. Two treatments were applied: one with natural densities of prey and the predators Chaoborus brasiliensis and the water mite Krendowskia sp. (Pr+), and another without predators (Pr-). Three enclosures (volume: 6.6 m 3 of water per enclosure) per treatment were installed in the sediment of the deepest area of the lake (5.0 m). At the beginning, Chaoborus larvae were present in Pr-enclosures, because of technical difficulties in preventing their entrance, but they virtually disappeared in the course of the experiment. Water mites were almost absent in Pr-enclosures. Chaoborus predation negatively influenced the Daphnia gessneri population, but not the populations of the copepods Tropocyclops prasinus and Thermocyclops decipiens and the rotifers Keratella spp. Death rates of Daphnia were generally significantly higher in the Pr+ treatment; Daphnia densities increased after the disappearance of Chaoborus in Pr-. Copepod losses to predation in the experiment may be compensated by higher fecundity, shorter egg development time, and lower pressure on egg-bearing females, resulting in a lower susceptibility to Chaoborus predation. The predation impact of water mite on microcrustaceans and rotifers in the experiment was negligible.

Fish but Not Macroinvertebrates Promote Trophic Cascading Effects in High Density Submersed Plant Experimental Lake Food Webs in Two Contrasting Climate Regions

“…In two out of the three temperate lakes, macroinvertebrate predators (G. lacustris) negatively affected the abundance of plant-associated macroinvertebrates, while in the subtropics, the plant-associated macroinvertebrates were not affected by the added shrimps. These differential effects of macroinvertebrate predation revealed in our experiment constitute the strongest contrast between the food webs in the two regions, and they contradict the idea that shrimp may exert a stronger predation pressure than Gammarus (or other invertebrate predators like Chaoborus larvae [25,81,82]) as suggested from earlier field evidence [20,32].…”

A long-term study on crustacean plankton of a shallow tropical lake: the role of invertebrate predation

“…In Lake Monte Alegre, Chaoborus consumed proportionately more copepods after the decline of the favourite prey Bosmina tubicen (Perticarrari et al, 2004). Researchers studying Lake Monte Alegre have suggested that copepods are less sensitive to the effects of predation by invertebrates due to reproductive traits, such as greater fertility and more rapid development of eggs (Castilho-Noll and Arcifa, 2007b), and behavioural, such as reverse vertical migration (Perticarrari et al, 2004;Minto et al, 2010). The population dynamics of copepods was not affected by Chaoborus larvae in mesocosms (Castilho-Noll and Arcifa, 2007b), and they are not preyed on by the mite (Cassano et al, 2002).…”

“…Researchers studying Lake Monte Alegre have suggested that copepods are less sensitive to the effects of predation by invertebrates due to reproductive traits, such as greater fertility and more rapid development of eggs (Castilho-Noll and Arcifa, 2007b), and behavioural, such as reverse vertical migration (Perticarrari et al, 2004;Minto et al, 2010). The population dynamics of copepods was not affected by Chaoborus larvae in mesocosms (Castilho-Noll and Arcifa, 2007b), and they are not preyed on by the mite (Cassano et al, 2002). Marine copepods detect predators by mechanoreception, and their myelinated nerves allow rapid conduction of impulses and consequent rapid escape movements (Buskey et al, 2012).…”

Competição, predação e variação temporal de microcrustáceos planctônicos no Lago Monte Alegre

“…Em experimento com mesocosmos, nem Tropocyclops prasinus nem Thermocyclops decipiens foram influenciados pela presença C. brasiliensis (Castilho-Noll & Arcifa, 2007b). As autoras atribuíram a vantagem dos copépodos à sua alta fecundidade, curto tempo de desenvolvimento do ovo e menor pressão sobre fêmeas ovígeras, que podem compensar a perda de organismos pela predação.…”