From lab to field: Transforming immunoassays for rapid microcystin-LR monitoring in Lough Neagh

The prevalence and distribution of freshwater harmful algal blooms (HABs) and their associated toxins have intensified, with seasonal occurrence representing a global phenomenon. Climate change and increased anthropogenic activities, including eutrophication and mismanagement of agricultural, industrial, and domestic waste, have heightened challenges in providing safe drinking water. Invasive shellfish species further exacerbate bloom severity by increasing water clarity and light penetration. This study describes the development and validation of a portable enzyme-linked immunosorbent assay (ELISA) for on-site detection of microcystin-leucine arginine (MC-LR), demonstrated during a major HAB event in Lough Neagh, Northern Ireland. A heterogeneous recombinant antibody-based competitive ELISA was adapted from a laboratory format to enable rapid field testing without bulky equipment. The assay detected MC-LR in water samples collected around Lough Neagh, and 16S rRNA amplicon sequencing confirmed the presence of the MC-LR-producing species Microcystis aeruginosa. This work demonstrates a practical strategy for translating laboratory immunoassays into deployable tools for rapid, on-site water quality monitoring.