2.4 Organisms greater than or equal to 50 micrometres in minimum dimension in the D-2 standard
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Statutory Documents - IMO Publications and Documents - Circulars - Ballast Water Management - BWM.2/Circular.42/Rev.2 – International Convention for the Control and Management of Ships' Ballast Water and Sediments, 2004 – (9 December 2020)... - Annex 2 – Technical Discussion for the Guidance to Ballast Water Sampling and Analysis for Trial Use in Accordance with the BWM Convention and Guidelines (G2) - 2 Indicative Analysis: Methodology and Approaches - 2.4 Organisms greater than or equal to 50 micrometres in minimum dimension in the D-2 standard

2.4 Organisms greater than or equal to 50 micrometres in minimum dimension in the D-2 standard

  2.4.1 Many of the methodologies for monitoring organisms less than 50 micrometres and greater than or equal to 10 micrometres in minimum dimension may also be valid for monitoring organism levels in this category. However, nucleic acid and ATP methodologies encounter the same problems as outlined in paragraphs 2.3.2 and 2.3.3; and monitoring chlorophyll a levels, through fluorometers or the PAM methodology described above, has limited value for this size category of the D-2 standard, as the majority of organisms in this category are likely to be zooplankton.

  2.4.2 Visual inspections may significantly underestimate the number of organisms in this size category due to the issues described in paragraph 2.3.8. However, the method may be robust enough to determine whether the BWMS is working at orders of magnitude above the D-2 standard based on a simple extrapolation from the sample to the D-2 standard. Detailed analysis may be needed to confirm this, especially when levels near the D-2 standard are encountered.

  2.4.3 Additionally, stereomicroscopy can also be used to identify viable organisms greater than or equal to 50 micrometres in minimum dimension. The sample should be concentrated appropriately. Viability assessment should be based on movements of intact organisms. This movement may be stimulated. In addition organ activity should be observed and fully intact non-moving organisms which show organ activity should be counted as living. Stains might also be used to help in viability determination – though methods are still under development. The viable organism numbers should be recorded and the numbers extrapolated up to the total volume of water filtered.

  2.4.4 If the results in paragraphs 2.4.2 and 2.4.3 show elevated levels of organisms, then this result will indicate that the D-2 standard is not being met.

  2.4.5 Further research must be encouraged; innovative methods for assessing for D-2 compliance, preferably based on in situ, automatic sampling and analytical procedures, should facilitate the most uniform implementation of the BWM Convention.

Parent topic: 2 Indicative Analysis: Methodology and Approaches
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