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Cull Policy

It is necessary for the NCMA to develop a cull policy to help reduce strain redundancy in the current collection, and to allow room for more diverse and scientifically interesting strains to be accessed. This is a critical part of collection management, particularly since it is becoming increasingly difficult to support new accessions with the current complement of curators and financial resources.

The NCMA (formerly CCMP) has not considered an organized culling of the phytoplankton collection in over 25 years. We hope that you, as our users, will agree with our decisions. There will be an opportunity for you to review our list and “Adopt-a-Strain” if you feel strongly about saving it.  However, unhealthy strains are not available to adopt.

We will not cull strains that have had their genome sequenced, type strains, authentic strains, or strains with a large publication record. Strains will only be culled from the live collection. It is important to note that no strains in the current cryopreserved collection will be culled (50% of our strains are known to survive cryopreservation). The following selection criteria will be considered to choose cull strains; at least 3 of these criteria must apply before a strain is culled:


  1. Multiple strains of same species, especially those that were collected at the same time from the same place and are rarely ordered (within the last 5 years).
  2. Multiple isolates of the same strain from same location and are rarely ordered (within the last 5 years).
  3. Strains growing so poorly that we cannot distribute them reliably without excessive time and effort.
  4. Strains contaminated with fungi that we have been unable to re-isolate.
  5. Rarely ordered strains (we have many strains that have never been ordered), defined as no requests for that strain in the last 5 years.
  6. No publication record for the strain.
  7. The strain is held by another collection.
  8. Marine strains will take priority (for saving) over freshwater strains.
  9. No cryopreserved strains will be culled.


Using these criteria and the decision-making flow chart (Figure 1), we estimate we can cull at least 20% (500 – 600 strains) of the algal collection without loss of any taxonomic diversity, geographical/ecological range, or scientific relevance. Importantly, it will free up capacity by the curators to allow us to actively access new and potentially interesting strains.

Every effort will be made to inform the original depositor of our intension to cull a strain. A cull list will be posted on our website giving at least 30 days notice prior to initiation of the cull process for strains on that list. We will reconsider a specific strain(s) cull if either the depositor, or the wider academic and/or business communities present convincing reasons to the head curator. 

Figure 1

Cull Flow Chart





View PDF version of the NCMA cull policy.

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