The pitfalls of using different classification systems to quantify biodiversity of cyanobacteria: A case study from Hong Kong rocky shores

Biodiversity studies of cyanobacteria are warranted because of their ecological significance and biotechnology potential but comparisons with existing data are complicated due to the existence of two classification systems. The pitfalls are illustrated using intertidal epilithic cyanobacterial species around Cape d'Aguilar, Hong Kong. A total of 33 species belonging to 16 genera and 8 families are recorded from the study site. Comparison of Hong Kong marine cyanobacteria, irrespective of their specific habitat, with other geographical regions reveals that the majority of Hong Kong species are widely distributed on other tropical shores around the world. However, very few of them are also recorded from temperate shores. Comparison of epilithic cyanobacteria on a world-wide basis demonstrates that the majority of Hong Kong epilithic cyanobacteria are not obligate epiliths and are recorded from other parts of the world as planktonic rather than epilithic. Due to inconsistency in taxonomic systems (i.e. "Geitlerian" or "Drouet"), comparison of Hong Kong cyanobacteria with other geographical locations shows misleading patterns of species richness. Consideration of the present species checklist (based on the "Geitlerian" classification system) under the "Drouet" classification system demonstrates an under-estimation of cyanobacterial species richness, highlighting problems when comparing world-wide distribution patterns of cyanobacteria. Taxonomic complexity, therefore, limits the exploration of biotechnology potential of cyanobacteria due to restricted number of species identification. It is recommended that rocky shore ecologists should use the "Geitlerian" system when describing cyanobacterial species composition.