In order to facilitate the monitoring of toxic algae, a multiprobe chip and a semi-automated rRNA biosensor for the detection of toxic algae in the field were developed. The biosensor consisted of a multiprobe chip with an array of 16 gold electrodes for the detection of upto 14 target species. The multiprobe chip was placed inside an automated hybridization chamber, which was in turn placed inside a portable waterproof case with reservoirs for different reagents. A peristaltic pump transferred the reagents across the flow cell (hybridization chamber) containing the multiprobe chip. For use of the device by laypersons, a lysis protocol was successfully developed so that manual rRNA isolation was no longer required. Only water sample filtration has to be done manually. The stand-alone system was evaluated using total rRNA isolated from Alexandrium minutum. The device processed automatically the main steps of the analysis and completed the electrochemical detection of toxic algae in less than 2. h in comparison to other routine monitoring methods that need at least up to one day for analysis. © 2011 Elsevier B.V.