Microbial planktonic communities in the Red Sea: high levels of spatial and temporal variability shaped by nutrient availability and turbulence

Abstract

The semi-enclosed nature of the Red Sea (20.2°N–38.5°N) makes it a natural laboratory to study the influence of environmental gradients on microbial communities. This study investigates the composition and structure of microbial prokaryotes and eukaryotes using molecular methods, targeting ribosomal RNA genes across different regions and seasons. The interaction between spatial and temporal scales results in different scenarios of turbulence and nutrient conditions allowing for testing of ecological theory that categorizes the response of the plankton community to these variations. The prokaryotic reads are mainly comprised of Cyanobacteria and Proteobacteria (Alpha and Gamma), with eukaryotic reads dominated by Dinophyceae and Syndiniophyceae. Periodic increases in the proportion of Mamiellophyceae and Bacillariophyceae reads were associated with alterations in the physical oceanography leading to nutrient increases either through the influx of Gulf of Aden Intermediate Water (south in the fall) or through water column mixing processes (north in the spring). We observed that in general dissimilarity amongst microbial communities increased when nutrient concentrations were higher, whereas richness (observed OTUs) was higher in scenarios of higher turbulence. Maximum abundance models showed the differential responses of dominant taxa to temperature giving an indication how taxa will respond as waters become warmer and more oligotrophic.

A denitrifying community associated with a major, marine nitrogen fixer

“…Further detail of the environmental conditions and microbial communities present at the Indian Ocean stations is given by Mazard and colleagues (), Bird and colleagues (), Zubkov and colleagues () and Wyman and colleagues (). For an overview of the conditions and the microbial communities characteristic of the mid‐Atlantic Ocean in late summer/autumn, see Schattenhofer and colleagues () and Rees and colleagues (), and for the Gulf of Aqaba and wider Red Sea, see Rahav and colleagues () and Pearman and colleagues ().…”

Disentangling the complex microbial community of coral reefs using standardized Autonomous Reef Monitoring Structures (ARMS)

“…The Red Sea presents a unique combination of environmental variables that have previously been shown to shape the planktonic community (Kürten et al, , ; Ngugi, Antunes, Brune, & Stingl, ; Pearman et al, ; Pearman, Kurten, Sarma, Jones, & Carvalho, ) and the metazoan component of the reef cryptobiome (Carvalho et al, ). However, knowledge of the factors structuring the composition and function of bacterial communities within coral reefs remains limited (Roik et al, ; Neave et al, ).…”

Diel dynamics and coupling of heterotrophic prokaryotes and dissolved organic matter in epipelagic and mesopelagic waters of the central Red Sea

“…Our results also revealed a consistent coupling between the diel dynamics of DOC sources and the changes in the size structure and composition of HP communities, at both the epipelagic and the mesopelagic layer of the sampled water column (0-700 m). As in its northern reaches, the central Red Sea is characterized by high salinity ($ 39.0) (Ngugi et al, 2012), low inorganic nutrients (Kürten et al, 2016) and relatively high water temperatures (24 C-32 C) in the epipelagic layer, and low oxygen concentrations in the mesopelagic layer (< 1 mg l −1 or < 9.2% AE 1.1% temperature corrected oxygen saturation) (Qian et al, 2011;Pearman et al, 2017). Similar to other oligotrophic regions, the Red Sea is frequently assumed to remain invariable for periods of weeks, however, it experiences its main seasonal phytoplankton bloom in epipelagic waters during winter (Calbet Although not yet explored for the Red Sea, phytoplankton temporal changes may affect HP distribution in the surface layer as reported elsewhere (Nagata, 2000;Lefort and Gasol, 2014).…”

“…There is evidence that the more active HP taxa are usually found in the HNA group (Schattenhofer et al, 2011;Vila-Costa et al, 2012) while LNA cells are known to include mostly oligotrophic taxa, such as the SAR11 clade (Hill et al, 2010;Schattenhofer et al, 2011;Vila-Costa et al, 2012). It has been reported that SAR11 represents the dominant HP group across the Red Sea, contributing approximating 60% to the HP community abundance at the surface (Ngugi et al, 2012, Pearman et al, 2017. Here, we found some evidences of a higher contribution of LNA cells in the epipelagic layer than in the mesopelagic layer, especially during day-time ( Fig.…”