Growth assessment and toxigenicity of microcystis in nutrient-enriched waters

Abstract

The growth of several harmful cyanobacteria (Microcystis) has increased worldwide as a result of numerous and rapid environmental alterations. In this study, the toxigenic cyanobacterium Microcystis was isolated from a water body in Mexico City (Pista Olímpica de Remo y Canotaje Virgilio Uribe) with the aim to investigate: (1) the influ-ence of increasing nitrogen (N) and phosphorus (P) on the growth of Microcystis and (2) the potential toxigenicity of Microcytis using mortality bioassays of Artemia sp. In 2017, two clonal strains (Mc17C2 y Mc17C3) of Microcystis were established in monoculture under controlled laboratory conditions. Microcystis strains were grown in a culture chamber in vitro with irradiance 19.6 µmol/m2/s with a 12 h light:12 h dark photoperiod, and at room temperature (~ 24 ± 2 ºC). Artemia sp. was cultured and juvenile organisms were used and feed on different quantities of Microcystis strains. Increasing N and P concentrations lead to higher growth rates of Microcystis; however, its optimum growth rate did not match with the highest nutrient concentrations in the cultures. Microcystis ingestion by juvenile Artemia caused 50 to 100 % of mortality in 48-72 h, when fed on abundance between 3 × 105 y 3 × 106 cells/ml. In general, Artemia was not susceptible to Microcystis ingestion within a time of 24 h. In conclu-sion, higher availability of dissolved nutrients in the water leads to increasing growth rates of Microcystis which may cause potential effects on zooplankton.