Iron enrichment from hypoxic hypolimnion supports the blooming of Raphidiopsis raciborskii in a tropical reservoir

•Blooms of R. raciborskii were investigated over a five years period in a tropical reservoir.•The importance of 17 variables was assessed using statistics and habitat comparison.•High bioavailability of iron triggered the blooms of R. raciborskii.•Iron's bioavailability was modulated by the hydrodynamic conditions of the water body.