Increased prokaryotic diversity in the Red Sea deep scattering layer

Area of Science:

• Marine microbiology
• Deep-sea ecology
• Biogeochemistry

Background:

• Diel vertical migration (DVM) actively transports dissolved organic matter (DOM) to the deep ocean.
• This process fuels heterotrophic bacteria and archaea in the mesopelagic zone.

Purpose of the Study:

• Investigate the impact of DVM on Red Sea mesopelagic prokaryotic diversity.
• Focus on the deep scattering layer (DSL) between 450-600m.

Main Methods:

• Analysis of physico-chemical variables (oxygen, nutrients, DOC).
• Prokaryotic diversity assessment using 16S rRNA gene sequencing.
• Multidimensional scaling analysis to compare microbial communities.

Main Results:

• Variability in physico-chemical conditions observed in mesopelagic depth profiles.
• Distinct seasonal indicator prokaryotes identified in the DSL (2-10% of sequences).
• DSL samples showed divergence from surrounding waters, clustering by depth; 21% of DSL species were unique.

Conclusions:

• Mesopelagic physico-chemical properties create a largely uniform prokaryotic community.
• The DSL significantly contributes to Red Sea mesopelagic prokaryotic diversity.
• DVM plays a crucial role in shaping deep-sea microbial ecosystems.