Effect of temperature, food quality and quantity on the feeding behavior of Simocephalus mixtus and Hyalella azteca: implications for biomanipulation

Abstract

Increasing temperatures in aquatic ecosystems have resulted in changes in the proliferation patterns and persistence of cyanobacteria, particularly Microcystis sp. In temperate lakes, large-sized herbivores such as Daphnia magna are used to control cyanobacterial blooms. The cladoceran, Simocephalus mixtus and the amphipod, Hyalella azteca are common in tropical and sub-tropical aquatic systems. Since both species are generalist feeders, we tested their ability to consume uni-cellular Microcystis sp. and Chlorella at different temperatures. Feeding rates and filtration rates at different temperatures (20, 25 and 30 °C) were quantified on diets of Chlorella vulgaris and Microcystis sp.; each diet separately at different concentrations (0.2, 0.5, 1.0 and 2.0 × 106 cell mL−1). Both the crustaceans were able to consume C. vulgaris and Microcystis sp. although at different rates depending on the food concentration and temperature. At 25 °C and a Microcystis sp. concentration of 2.0 × 106 cells mL−1, H. azteca fed up to 60 × 104 cells ind−1 h−1 of Microcystis sp. which was even greater than its feeding rate on C. vulgaris. Simocephalus was able to consume Microcystis sp. although at significantly lower rates as compared to C. vulgaris. Our experiments show that H. azteca can feed well on Microcystis sp. Combined with control in fish predation pressure, both crustacean species could be used in top-down control, but further investigation on a large scale with these organisms is necessary to propose new alternatives.