Toxin-producing algae in coastal waters produce serious physical harm to fish and shellfish and their habitats, as well as skin infections in swimmers and food poisoning in those who eat the affected fish. The economic and public health consequences of these harmful algal blooms are on the rise due to enhanced proliferation as a result of human activity. In addition, very small quantities are necessary to produce toxic effects. Current methodologies for detection are problematic, with no cost-effective and timely means for using molecular techniques to distinguish between toxic and non-toxic strains that are often structurally similar. Researchers working on the ‘Development of an rRNA-biosensor for the detection of toxic algae’ (ALGADEC) project produced a hand-held device combining molecular and electrochemical methods to analyse in situ the concentration of toxic algae. The device relies on an electrochemical rRNA (ribosomal ribonucleic acid) sensor that produces an electrical current proportional to the amount of rRNA specific to toxic algae. Thus, the hand-held unit is cost-effective, provides immediate results and is easy to use by fish farmers, water quality monitoring agencies and tourist administrations, among others. Commercialisation of the ALGADEC device is anticipated to have an important impact on the European seafood industry, tourism and public health. In addition, adaptation of the methodology for detection of other pathogens could have wide-reaching influence on numerous other sectors of the economy.