CEMS-RI Weekly Seminar on September 22, 2021 by Dr. Mario De Stefano

PRESENTS AN​ ONLINE SEMINAR             

Biodiversity and Ecological Significance of  Benthic Diatom Communities Associated with Seagrasses and Corals of the Arabian Gulf

Date      : Wednesday, September 22, 2021                                                                                                                           

Time     : 10:00 – 10:30 AM                                                                                                                                      

Location: Online Zoom Room - Join Meeting

Speaker:​ 

Abstract:

The present work is a first contribution to the knowledge of biodiversity and ecology of benthic diatoms associated with the phanerogams and corals occuring in the Arabian Gulf. To achieve this goal, seagrass (Halodula uninervis, Halophila ovalis, Halophila stipulacea) and coral (Acropora sp., Porites sp., and Platygyra sp.) samples were collected during two sampling surveys (winter and summer) from various stations spread along the Saudi coast in the Gulf, and their associated diatom communities were examined.

The analysis of collected samples with Scanning Electron Microscopy (SEM) showed that while the species richness of diatoms associated with seagrasses decreased between winter (38) and summer (20), the number of those associated with corals increased from 30 (winter) to 40 (summer). Higher total abundance values of seagrass-associated diatoms were recorded in winter (1618-11863 cells/mm2 versus 260-3200 cells/mm2 in summer). The opposite trend was observed with coral-associated diatoms, whose total abundances increased from few hundreds of cells/mm2, in winter, to 200-600 cells/mm2, in summer. It is worth noting that the winter abundance values of coral-associated diatoms were found to be 10 to 100 times lower compared to those of diatoms associated with seagrasses, depending on the sampling location. Cocconeis species prevailed the diatoms communities associated with seagrasses, during both seasons. The highest abundance of Cocconeis diatoms (>10,000 cells/mm2) was recorded in winter, with Halophila plant species. The analysis of summer coral samples showed the dominance of diatom genera characterized by erect and motile growth forms such as Lichmophora, Grammatophora, Fragilaria, and Navicula, which were also responsible for the highest abundance values recorded during this latter season. These erect-form diatoms were found to colonize mainly the dead areas of the corals examined, making therefore these organisms favorable biogenic substrates for the colonization and proliferation of diatoms during summer.

The findings of this study shaded the light on one of the important components of seagrass and corals systems in the Arabian Gulf and contribute to better understand the functional ecology of these essential habitats.  

All faculty, researchers and graduate students are invited to attend