Cyanobacteria in aquaculture systems: linking the occurrence, abundance and toxicity with rising temperatures

The presence of toxic cyanobacteria in aquaculture systems is a matter of concern due to its capability to produce toxin known as microcystin. This study was carried out to determine the presence, abundance and toxic potential of cyanobacteria in selected aquaculture systems in Perak, Malaysia, as well as to identify the potential main trigger of toxic cyanobacterial blooms in aquaculture water. In this study, a total of 40 freshwater fish ponds were sampled from 10 different aquaculture farms in Perak, Malaysia. Results revealed that the most frequently found cyanobacterial taxa in Perak aquaculture water was Microcystis spp., where it was detected in all of the studied ponds. During the sampling period, 75 % of the sampled ponds water contained unsafe levels of microcystin with concentrations up to 295.86 A mu g MC-LR equivalent L-1. This study also discovered that a combination of temperature and pH was the key environmental factor that triggered the proliferation and toxicity of cyanobacteria, whereby temperature was statistically proven to be a more powerful predictor in comparison with pH. This study has implied that cyanobacteria can present health risk to human through aquaculture fish consumption. Moreover, the risk posed by cyanobacteria in aquaculture systems will be amplified by the influence of global warming, with rising water temperatures up to 32 A degrees C.