Are there Invasive Planktonic Microbes ?
Résumé
The translocation of species by human activities is a problem that increases with the globalization. However, the examples of
non-indigenous or exotic planktonic microbes can be questioned as they predominantly have cosmopolitan distributions and
natural mechanisms for wide dispersion. In reality, the categorization of any species as non-indigenous requires solving two
difficult issues: knowledge of where the ‘natural’ population is, and demonstration of a substantial geographic discontinuity
between the supposed source and the introduced populations. With regard to planktonic microorganisms, a non-indigenous
taxon could have been previously unnoticed during routine microscopical analyses due to: A) difficult identification at the
species level in routine observations such as for the diatoms (Pseudo-nitzschia, Skeletonema, Thalassiosira, Pleurosigma),
unarmoured dinoflagellates (Karenia, Karlodinium) and Raphidophytes, and B) species with strong interannual fluctuations
of abundance, only detected during bloom periods when they are misinterpreted as newcomers (i.e., Coscinodiscus wailesii
or Trieres chinensis, junior synonyms of C. cylindricus and T. regia, respectively, or Gymnodinium catenatum). Rather than
attempting to add to the lists of non-indigenous species with planktonic microbes, the monitoring surveys should also pay
attention in the less common species with important fluctuations of abundance, independent of tentative labels as exotic or
indigenous, because they are potentially useful as bio-indicators of environmental changes.
Mots clés
Ballast Water Management
Biological Invasions
Climatic Bio-indicators
Exotic Protist
Non-indigenous Dinoflagellate
Alien diatom
Introduced phytoplankton
Ballast Water Management Biological Invasions Climatic Bio-indicators Exotic Protist Non-indigenous Dinoflagellate Alien diatom Introduced phytoplankton
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