Objective In light of escalating anthropogenic activities impacting aquatic ecosystems and global climate change, the frequency and magnitude of red tide occurrences have been steadily increasing year after year. Red tide has evolved into a marine ecological catastrophe that poses a grave threat to oceanic ecological environments, socio-economic development, and public health. Fujian Province possesses abundant marine resources; however, the rapid progress of marine aquaculture is hindered by the occurrence of red tide. Therefore, the development of precise, rapid, and specific detection techniques for harmful algae is imperative to enable early monitoring and warning systems for red tides.

Methods The study evaluated a rapid detection method that combined recombinase aided amplification (RAA) with LbCas12a nuclease. This method was tested using field red tide samples and pilot applications, with Karenia mikimotoi, Karlodinium veneficum, and K. brevis serving as representative species. The core principle of the RAA-LbCas12a method involved designing amplification primers and crRNA that specifically targets the internal transcribed spacer (ITS) region unique to the desired algal species, which enabled rapid amplification of the target nucleic acid, followed by analysis of the amplification products. Additionally, lateral flow strips were utilized for visual interpretation of the detection results.

Results The RAA-LbCaas12a assay demonstrated high accuracy in detecting target microalgae in field red tide samples, even at concentrations as low as 10 cells/mL (representing only 0.1% of the total cells present in red tide samples). While the target microalgae in environmental samples were consistently detected multiple times during the 65-day pilot application, it demonstrated a large level of concordance with the results obtained from colloidal gold immunoassay strips and microscopic observations. Importantly, no significant instances of false positives were observed.

Conclusion Field application data demonstrate that the RAA-LbCas12a technology exhibits remarkable sensitivity, specificity, reliability, and operational simplicity. Additionally, this technology has proven to be highly applicable for the field detection of various red tide algae species. The RAA-LbCas12a technology only requires a portable rapid detection toolkit, enabling field inspectors to promptly perform on-site microalgae testing, which holds immense significance in enhancing red tide monitoring and early warning capabilities, as well as strengthening measures for preventing and controlling marine ecological disasters.