Speaker 1: Dr. Tamara Huete-Stauffer Title: Prokaryotic diversity: the deep scattering layer
Abstract: Prokaryotes are responsible for a major fraction of the cycling of nutrients and carbon in the ocean, especially in oligotrophic waters like the Red Sea. In this study, I analyze the diversity of prokaryotes in the deep scattering layer (DSL), a layer around 500 m where mesopelagic fish concentrate during the day. The diel migration of animals from surface to deep layers provides a mechanism for the enrichment and transport of labile dissolved organic matter (DOM) to the deep ocean and can contribute to the diversity of prokaryotes in the mesopelagic. In this seminar I will show the results of 16S metagenomics focusing on the DSL, its variability and its contribution to the overall diversity in the Red Sea.
Speaker 2: Dr. Ghaida Hadaidi Title: Bacterioplankton community composition in coastal waters of the central Red Sea
Abstract: Planktonic bacteria play a critical role in the biogeochemistry of tropical ecosystems. Microbial community composition is linked to environmental factors, usually assumed to change little in low latitude waters. We have just started to unveil the seasonal dynamics of Red Sea bacteria. Herein, we compare the bacterial community dynamics of two coastal sites in the central Red Sea. Surface water samples for flow cytometric characterization and 16S rRNA analysis were collected monthly in 2018 from KAUST Harbor and Abu Shusha reef. The two sites differed in temperature; 24.6˚C- 34.2˚C at the harbour and 25.5˚C- 32.4˚C at Abu Shusha; and nutrient availability. For instance, dissolved organic carbon concentration was higher at KAUST Harbor (103.83 ± 18.29 vs. 83.2 ± 9.07 in the reef). Prochlorococcus cyanobacteria were only consistently found at Abu Shusha. Whereas the total abundance of heterotrophic bacteria was similar (6.04 ±1.45 and 5.24 ± 1.45 105 cells in the reef and harbor, respectively), the contribution of high nucleic acid content cells, typically prevalent in eutrophic environments, was systematically higher in the harbor (47% vs. 33%). As expected, we also found a different bacterial community composition between the two sites. The most abundant genera of free-living bacteria were Synechococcus (5.9 % to 45.7%), SAR11 (1.2% to 34.1%) and Prochlorococcus (0.14% to 25.5%) The genus Synechococcus was particularly abundant in the harbor, whereas SAR11 and Prochlorococcus dominated Abu Shusha reef. Our results show that differences in bacterial abundance and diversity were patent even at short distances along the inshore-offshore gradient.
Speaker 1: Dr. Tamara Huete-Stauffer
Speaker 2: Dr. Ghaida Hadaidi