A Long‐Term Study on the Effect of Cyanobacterial Crude Extracts from Lake Chapultepec (Mexico City) on Selected Zooplankton Species

Many urban lakes in Mexico City such as Lake Chapultepec are infested with high densities of cyanobacteria, particularly Microcystis. We tested the effect of cyanotoxins from cyanobacterial crude extracts on the demographic variables of zooplankton. The rotifers Brachionus havanaensis and Brachionus calyciflorus, and the cladocerans Ceriodaphnia dubia and Moina macrocopa were used for the assays. Temperature effects on the response of B. calyciflorus and 2 clones of M. macrocopa were tested. We hypothesized that with an increase in cyanotoxin concentration and temperature there would be an increase in the adverse effect on the test species and that the clone of Moina previously exposed to cyanobacteria from Lake Chapultepec would be more resistant to the cyanotoxins. Demography experiments showed that B. havanaensis was more sensitive than C. dubia. The negative effect of the cyanobacterial crude extract on B. calyciflorus was greater at 30 °C than at 20 °C or 25 °C. The strain of M. macrocopa isolated from Lake Chapultepec was more resistant to the cyanotoxins than the strain that had not been previously exposed to the cyanobacteria. The present study indicated that cyanobacteria in Lake Chapultepec are highly toxic and, considering the recreational use of this lake, should be controlled. Environ Toxicol Chem 2020;39:2409–2419. © 2020 SETAC Effects of urban lake microcystins on zooplankton.