MC-LR immunoassays in Lough Neagh
The prevalence and distribution of freshwater harmful algal blooms (HABs) and their associated toxins have  intensified, and their seasonal appearance is a naturally occurring global phenomena. Changing climate, increased anthropogenic activities such as eutrophication and mismanagement of agricultural, industrial and domestic waste have exacerbated the burden of providing clean potable drinking water and is of immediate concern. Additionally, the unnatural clarification of water systems by invasive shellfish species enhances light penetration, further intensifying the severity of harmful algal blooms. This study presents the development and validation of an enzyme-linked immunosorbent assay (ELISA) modified for portability to detect microcystin-leucine arginine (MC-LR) on-site, demonstrated during a  major HAB event in Lough Neagh, Northern Ireland. A heterogenous recombinant antibody-based competitive (ELISA) towards MC-LR was adapted from a standard laboratory-based ELISA to provide on-site water testing results within minutes, without the requirement of bulky incubators or laboratory-based readers. The assay successfully determined the presence of MC-LR in water samples around the coast of Lough Neagh, Northern Ireland, and 16S rRNA amplicon sequencing confirmed the presence of MC-LR producer species Microcystis aeruginosa. This work showcases a practical approach for translating lab-based immunoassays to deployable field-based testing, enabling fast, on-site water quality monitoring.