Assessing ultraphytoplankton and heterotrophic prokaryote composition by flow cytometry in a Mediterranean lagoon

Abstract

In the eutrophic Ghar El Melh Lagoon (GML, Tunisia), the distribution of heterotrophic prokaryotes, pico- and nanophytoplankton was studied at five stations in November 2012 at the single cell level, along with environmental factors. Flow cytometry analysis of ultraplankton (<10 μm) resolved (i) two heterotrophic prokaryote groups, low and high nucleic acid contents (LNA and HNA, respectively), and (ii) eight to nine ultraphytoplankton groups (cryptophyte-like cells, two nanoeukaryote subgroups, two picoeukaryote subgroups and three Synechococcus-like cells subgroups). Prochlorococcus was not detected. According to redundancy analysis (RDA), a significant difference was found in the distribution of the ultraplankton between stations (F = 2.61, p < 0.05); maximum proliferations of heterotrophic prokaryotes were observed in the inner parts of the lagoon at stations 3, 4 and 5 affected by urban, agricultural and industrial discharges. Ultraphytoplankton concentrations were the highest near the outlet of the lagoon at stations 1 and 2 influenced by freshwater outflow and oligotrophic Mediterranean water inflow, respectively. At station 1, the large ultraphytoplankton concentration derives from the high abundance of cryptophyte-like cells favoured by the freshwater outflow whereas at station 2, the input of oligotrophic Mediterranean water enhanced the abundance of Synechococcus and picoeukaryotes at the expense of nanoeukaryotes. Two trophic regimes were thus differentiated in GML.

Response of Phytoplankton Communities to Variation in Salinity in a Small Mediterranean Coastal Lagoon: Future Management and Foreseen Climate Change Consequences

“…Initially dominating the small fraction of the phytoplankton community, at the end of the experiment picocyanobacteria had decreased in favor of picoeukaryotes and nanophytoplankton. Synechococcus is the dominant picophytoplankton taxon in rich coastal waters, which can explain the absence or paucity of Prochlorococcus-like detection over both experiments, as also observed in Ghar El Mehl lagoon (Tunisia) [77]. Synechococcus dynamics are strongly influenced by salinity [78].…”

The toxicity of cooking oil fumes on human bronchial epithelial cells through ROS‐mediated MAPK, NF‐κB signaling pathways and NLRP3 inflammasome

“…The apoptosis ratio was detected with flow‐cytometry assay 37 . As shown in Figure 4, with the increase of COFs concentration (200, 400, and 600 μg/ml), apoptosis ratios were 10.85 ± 1.1%, 19.7 ± 1.3%, and 24.6 ± 1.8% respectively, which were significantly higher than that in the control group (5.6 ± 1.4%).…”

“…The apoptosis ratio was detected with flow-cytometry assay. 37 As shown in Figure 4, with the increase of COFs concentration (200, 400, and 600 μg/ml), apoptosis ratios were 10.85 ± 1.1%, 19.7 ± 1.3%, and 24.6 ± 1.8% respectively, which were significantly higher than that in the control group (5.6 ± 1.4%). Moreover, with the increasing concentrations of COFs, the percentages of apoptosis cells increased significantly and showed a dose dependent manner.…”

Occurrence of Polycyclic aromatic hydrocarbons (PAHs) in mullet (Liza aurata) from Bizerte and Ghar El Melh Lagoons (Tunisia) and associated human health risk assessment

“…It's a lagunar complex classi ed as Ramsar site (Ramsar, 2007) sheltering a signi cant number migratory birds (Ayache et al, 2009). It includes three wetlands of about 35 km 2 (the main lagoon, Sabkhet El Oua and Sabkhet Sidi Ali El Mekki) and with depth varying between 0.2 and 3.8 m (Dhib et al, 2017;. This wetland communicates with the opened sea by a single channel, to the east, called "El Boughaz" with an average depth of 0.8 m (Dhib et al, 2013).…”

“…The Lagoon of Ghar El Melh is an aquatic ecosystem in northern Tunisia that has ecologic and economic importance. It is a Ramsar wetland with various dwellings for migrating sh and birds (Dhib et al, 2017). Indeed, this ecosystem is subjected to stresses, in fact the anthropogenic activities (releases of municipal and industrial wastewater, releases of the drainage system and the shing operations) (Moussa et al, 2005), leaded to the decline of its biodiversity and particularly, the decrease of shery resources, contributing to a decrease in shing income (Béjaoui et al, 2018;Moussa, Baccar, and Ben Khemis, 2005).…”