Combined effect of crude extracts from a cyanobacteria consortium and temperature on the demographic characteristics of Ceriodaphnia dubia (Cladocera)
摘要
Cyanobacterial blooms affect zooplankton feeding due to mechanical (blooms) and chemical interference (cyanotoxins). In Lake Zumpango, the frequency of toxin-producing cyanobacterial consortia has increased in the last decade due to elevated nutrient loads and higher average water temperature. Here, we evaluated the combined effects of crude cyanobacterial extracts from Lake Zumpango and temperature on the demography of Ceriodaphnia dubia. We conducted tests to estimate the median lethal concentration using eight proportions of diluted crude extracts containing microcystin-LR at 12.6, 18.9, 25.3, 31.6, 37.9, 44.2, 50.6, and 56.9 µg L− 1 and three temperatures (18, 23, and 30 ± 1 °C). Toxicity tests (population growth and life table) were conducted using sub-lethal concentrations (1.4, 2.9, 5.8, and 8.8 µg L− 1) at the above-mentioned temperatures. The LC50 results ranged from 18.10 to 38.13 µg L− 1 eq MC. The population growth rates ranged from 0.06 to 0.20 d− 1. At all temperatures, the growth rate of C. dubia exposed to crude extracts with 5.8 and 8.8 µg L− 1 was significantly lower than the controls. The life table experiments indicated that the combined effects of temperature and the cyanobacterial extract resulted in a 25% decrease in the survivorship as compared to controls. During blooms, which are more prevalent in warm (> 20 °C) conditions, cyanobacteria decompose and cyanotoxins are liberated into the medium. This research contributes to understanding the combined effect of toxin-producing cyanobacteria and temperature on cladocerans, and implications under warmer conditions.