Are there Invasive Planktonic Microbes ?

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Gómez, Fernando | Artigas, Luis Felipe

Edité par CCSD ; Opast Publishing Group -

International audience. The translocation of species by human activities is a problem that increases with the globalization. However, the examples ofnon-indigenous or exotic planktonic microbes can be questioned as they predominantly have cosmopolitan distributions andnatural mechanisms for wide dispersion. In reality, the categorization of any species as non-indigenous requires solving twodifficult issues: knowledge of where the ‘natural’ population is, and demonstration of a substantial geographic discontinuitybetween the supposed source and the introduced populations. With regard to planktonic microorganisms, a non-indigenoustaxon could have been previously unnoticed during routine microscopical analyses due to: A) difficult identification at thespecies 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 fluctuationsof abundance, only detected during bloom periods when they are misinterpreted as newcomers (i.e., Coscinodiscus wailesiior Trieres chinensis, junior synonyms of C. cylindricus and T. regia, respectively, or Gymnodinium catenatum). Rather thanattempting to add to the lists of non-indigenous species with planktonic microbes, the monitoring surveys should also payattention in the less common species with important fluctuations of abundance, independent of tentative labels as exotic orindigenous, because they are potentially useful as bio-indicators of environmental changes.

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