Several methods have been developed to monitor harmful algal bloom (HAB) species. Light microscopy is commonly used due to its widespread availability and ability to connect new findings with historical data. However, microscopy can be time-consuming when analyzing individual samples and requires taxonomic expertise, making it challenging to differentiate between morphologically similar species.
Flow Imaging Microscopy, specifically via FlowCam, integrates flow cytometry and microscopy principles to capture, identify, and electronically quantify particles in a fluid medium. The FlowCam 8100 instrument has been utilized in various research studies, including those focusing on microplastics, lipids, cell biovolume, and phytoplankton. Compared to traditional microscopy, FlowCam offers a more efficient analysis process, albeit potentially with slightly reduced taxonomic resolution and cell concentrations. (Pictured here, Alexandrium catenella as imaged by FlowCam)
Sandwich hybridization assay (SHA) is another technique that enables rapid (<1 h) taxon or species-specific plankton identification and quantification using ribosomal RNA (rRNA)-targeted oligonucleotides and has been applied to several HAB species. Comparisons between qPCR, SHA, and microscopy, have demonstrated strong agreement for HAB cell quantification.
Each approach (microscopy, FlowCam, SHA) has been used for HAB detection and monitoring. Still, they have not been uniformly compared despite marked differences regarding equipment, quantification mechanism, cost, training, and other attributes. Given the increasing emphasis on networking technologies to enhance bloom warnings, reconciling datasets generated by these tools is a critical management need. This study focused on the saxitoxin-producing 'red tide' dinoflagellate Alexandrium catenella because it causes paralytic shellfish poisoning, has an expansive biogeographic distribution, and is monitored worldwide. The authors present data comparing the three different techniques and suggest that the results would be broadly applicable to several HAB species.
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