Cyclic peptide cyanobacterial toxins, in particular Microcystis aeruginosa, pose a serious health risk to humans and animals alike [1], [2]. Occurring mostly in fresh and brackish water, they have been identified to cause cancer promotion and liver damage [3]. Herein, we describe a portable, microfluidic-based system for in-situ detection of algal toxins in fresh water. The Atalanta system is a novel, portable and sample-to-answer platform for the detection of toxic cyanobacteria – Microcystin-LR in fresh water. Atalanta utilises the partnership of highly-specific recombinant chicken anti-microcystin antibodies, prepared in-house, with a 3D-printed ‘LASER-photo¬diode’ fluorescent detection method, also developed in-house. A competitive immunoassay format is utilised to detect free toxin. Furthermore, dissolvable-film (DF) based flow-actuation facilitates full assay inte¬gration. This new approach will form the basis of a cost efficient, USB-controlled water quality monitoring system. The Atalanta detection system consists of two components; the microfluidic Atalanta disc and the disc-holder. The Atalanta disc-holder was fabricated and assembled from a 3D-printed casing, with electronic components housed in device. The 5-layered microfluidic disc consists of five reservoirs, each with a separate venti¬lation, aligned radially with inter-connected microchannels. Each reservoir represents a functional assay step. First, microcystin conjugate is coated to the functionalised surface of the reservoir 3 prior to assembling the disc. A freshwater sample in reservoir 1 is pre-incubated with recombinant antibodies labelled with fluorophore (Alexa 647) in reservoir 2. This is then spun into reservoir 3 for detection through a competitive immunoassay using Microcystin-LR. Low fluorescence signal indicates high Microcystin-LR concentration in the sample.