For managing the risk of domoic acid, monitoring the water column for domoic acid content is beyond the scope of current technologies.
Unfortunately, P. multiseries which produces the toxin and P. pungens (which does not produce significant amounts of the toxin) are virtually identical under the standard light microscope. Therefore, a current means to identify the toxic species from non-toxic is by the scanning electron microscope (SEM), a method that magnifies cells about 20,000 times.
An important step in managing toxic blooms is to be able to identify species of algae.How can you tell which is which? With the Scanning Electron Microscope (SEM), fine detail in the structures in these organisms can be seen (we are looking at only one-half of the silicate shell of the diatom. Both parts fit together like a box with a lid). Under high magnification, more detail becomes apparent as we look down between the "ribs" or striae, in the photomicrograph.
The SEM below show three species of Pseudo-nitzschia: (1) pseudodelicatissima, found in a recent record-setting toxic Pacific Northwest bloom; (2) multiseries; and (3) pungens. Notice the small pores between the striae. In order to identify and differentiate between some species of this diatom, for example between P. pungens and P. multiseries, examination of these pores is necessary. Note that pseudodelicatissima has just 1 row of square pores between its striae (rib-like structures); multiseries has 3 to 4 rows; and pungens has 2 to 3 rows, with larger pores than multiseries. A magnification bar equivalent to 2 microns is shown in the first photo. One thousand microns equal one millimeter.