Toxin-producing Microcystis aeruginosa: A trade-off in the vertical distribution of three Daphnia species as predicted by the ideal free distribution with costs model

摘要

Daphnia hyalina, D. galeata, and D. ambigua were exposed to the cyanobacterium Microcystis aeruginosa in 30 cm temperature-stratified columns. Changes in egg ratio, lipid index, length, and growth were recorded over 3 day experiments. Spatial distributions were recorded during 6-hour constant light experiments and 3 day fluctuating light experiments. D. hyalina and D. galeata stayed in the upper half of the column in temperatures of 18--22°C when exposed to M. aeruginosa. D. ambigua remained between 10--19°C regardless of food type. For across all experiments, depth and temperature ranges were narrowest in treatments with M. aeruginosa. D. ambigua incurred costs to both spatial distributions and fitness parameters. D. hyalina and D. galeata incurred costs to fitness but not spatial distribution when M. aeruginosa was present in the experimental system. Future work should investigate the natural lake systems containing the Daphnia used in these experiments to tease out the influences on temperature and depth choices of the animals.