Benthic marine diatoms from tropical environments are still poorly documented, despite their high diversity. Coral reef biotopes of the Mascarene Islands (Western Indian Ocean Archipelago: Réunion, Mauritius, Rodrigues Islands) provide the opportunity to study a large part of their diatom community: the abundant small-sized Achnanthales treated here. Diatoms of other environments of very variable nutrient status were studied in Réunion and Rodrigues Islands and include areas of both low and high anthropogenic impact.
This monograph describes taxa of seven genera, upon which Cocconeis Ehrenberg was particularly diverse. Scanning and light microscope images document and illustrate a total of 59 taxa, eight of them are new descriptions from these islands. This study serves as a basis for further investigations in the Mascarenes, Réunion the Rodrigues Islands and other tropical areas.
The Mascarenes 5
Diversity of coral reef diatoms 7
Preliminary remarks 8
Material and methods 8
Order Achnanthales Silva 11
New taxa described 12
Taxa description 13
Taxa with unfixed classification 40
General comments about the Mascarene small-sized Achnanthales 43
New taxa and endemism in Mascarenes 44
Characteristics shared by taxa close or affiliated to Cocconeis peltoides 46
Small-sized taxa and the importance of SEM observations 47
LM Plates 56
SEM Plates 70
Taxonomic Index 232
"The biodiversity and particularly the diversity of diatom floras of coral reef environments are high. In spite of this, the microphytobenthic communities of tropical reefs are poorly documented.
The Mascarene Archipelago, situated in the Indian Ocean near the Tropic of Capricorn, includes the islands of Réunion, Mauritius and Rodrigues. The coral sediments fringing the lagoons of the islands are inhabited by diverse diatom communities, however, previous studies mainly focussed on diatoms living in freshwater habitats of the islands.
This monograph deals with the small-sized and so far poorly documented taxa of order Achnanthales Silva found on coral reefs of Réunion and Rodrigues Islands revealing their high diversity. The authors describe 59 taxa belonging to or related to the genera Achnanthes Bory sensu stricto (2), Achnanthidium Kützing sensu Round (8), Amphicocconeis De Stefano et Marino (2), Anorthoneis Grunow (1), Cocconeis Ehrenberg (41), Planothidium Round et Bukhtiyarova (3), Vikingea Witkowski, Lange-Bertalot et Metzeltin (2) and eight of these are new for science. Genera and species are arranged alphabetically except taxa with unfixed classification that are described at the end of the taxonomic part. For each taxa taxonomic information, morphological features (length, width, number of striae in 10 μm on both sternum and raphe valva), descriptions in Latin and in English, as well as habitat and comparison to other species are provided. Taxa are illustrated by good quality, light and scanning electron microscopic micrographs. All the 62 small-sized Achnanthales taxa observed during the four-year survey are listed at the end of the monograph.
On the whole, this monograph is really valuable providing insight into such a diverse, but previously hardly investigated tropical diatom assemblage. It can be useful for all, who are interested either in the diatoms living on coral reefs or in the small-sized representatives of order Achnanthales."
– M. Duleba, Acta Botanica Hungarica 54 (3-4), 2012