The analysis of ballast water has to follow the principle considerations for the chemical, physical, microbiological and biological analysis of seawater, which in fact represents one of the most complex natural solutions.
Since the quality standards for ballast water to be re-discharged to the sea set-up by the IMO is split into three different organism size classes (>50µm, <10µm<50µm, bacteria) covering three different types of feeding (autotroph =algae, heterotrophy=animal, chemotroph=bacteria) the necessary analytics to distinguish live from dead organisms in a ballast water sample is as complex.
Picture: Counting plankton with the Bogorov plankton chamber
Counts of live organisms under the microscope is the traditional way of analyzing water samples. However, the accuracy of this method lies within the eye of the person that counts and depends from experience and taxonomic knowledge. Also, counts of marine organisms in the range of >10µm<50µm demand additional devices for counting such as compartimented plankton chambers or microscopic count plates (e.g. Neubauer chamber).
Chemical analysis combined to counts of live organisms is the traditional method for the analysis of the bacterial load of a water sample. The sample is incubated for 24/48 hours on a special substrate that accelerates the growth of single bacteria towards small colonies, which are detected by alterations in the color of the substrate.
Especially for microalgae there are different staining methods to distinguish live from dead cells and flow cytometry may be applied for counts of viable phytoplankton cells.
Recently chemical methods to distinguish live from dead organisms have been further developed for the application within the frame of ballast water analysis. These methods try to convert the concentration value of a chemical substance found in the sample expressed as milligram, microgram or even pictogram per volume unit, e.g. pg/µl, into a numerical value expressed as number of organisms per volume unit, e.g. organisms/ml. This in fact is the most critical step in the development of these methods for ballast water analysis.
Before new analytical methods, that proved their applicability for ballast water analysis, are turned into standard methods on the international level, they still have to be validated. For this validation a sample will be analyzed by a classical, commonly accepted and reliable analytical method and in parallel by the new analytical method. The comparison of the results from both analysis’ will give indications on the reliability of the new analytical method.
Picture: Set of laboratory filters for staged filtration of plankton