There are numerous approaches for detecting these potentially devastating events, and they include assays, analyses, and remote detection. Here we discuss three common methods for HAB detection: mouse bioassay, high performance liquid chromatography (HPLC), and optical detection. There are advantages and limitations with each of these techniques; the best detection method depends a lot on the research question being investigated.

An assay is a method that results in a single response. For example the mouse bioassay provides the total toxicity of the sample injected into a mouse, regardless of which toxins are causing the overall toxicity.
This method works well for monitoring purposes and most states have great success using this procedure to regulate fishing and shellfish practices. However, this method is not adequate for scientists interested in applied research. To understand the causes of toxin production and variability it is necessary to measure the presence of individual toxins and their concentrations rather than an overall toxicity.
An analysis is different from an assay in that all contributing toxins can be distinguished. HPLC analyses seek to separate and quantify all toxins individually in the sample.
This method allows for the separation, identification, and quantification of each toxin derivative present and its concentration. Although appropriate for applied research purposes, HPLC methods do not supply results quickly enough to be the best method for establishing early warning systems. By the time the sample is processed the algal bloom may worsen, impacting ecosystem and public health before a warning can be issued.
The methods above are limited by the time it takes to collect and process water samples. There is a need for rapid, non-invasive techniques that cover large areas. Given that algal blooms are often associated with dramatic water discolorations (e.g., red, brown tides), ocean color detection may help migitate these devastating events. Approaches include in situ ("in place"; e.g., TSRB ocean color buoys) and remote sensing methods. These may: 1) be useful for long term monitoring, 2) allow early warning systems to be implemented, 3) allow tracking of existing blooms, and 4) be useful in determining what causes blooms to form.
Although ocean color detection doesn’t measure toxicity, it provides substantial information about what is in the water column (e.g., phytoplankton, colored non-algal particles, colored dissolved organic material). It is rapid and allows for large spatial coverage. Also, this method can help determine the types of phytoplankton responsible for the bloom.