Long-term, basin-scale salinity impacts from desalination in the Arabian/Persian Gulf

Functional and structural responses of a halophilic consortium to oily sludge during biodegradation

Biotreatment of oily sludge and the involved microbial communities, particularly in saline environments, have been rarely investigated. We enriched a halophilic bacterial consortium (OS-100) from petroleum refining oily sludge, which degraded almost 86% of the aliphatic hydrocarbon (C10-C30) fraction of the oily sludge within 7 days in the presence of 100 g/L NaCl. Two halophilic hydrocarbon-degrading bacteria related to the genera Chromohalobacter and Halomonas were isolated from the OS-100 consortium. Hydrocarbon degradation by the OS-100 consortium was relatively higher compared to the isolated bacteria, indicating potential synergistic interactions among the OS-100 community members. Exclusion of FeCl2, MgCl2, CaCl2, trace elements, and vitamins from the culture medium did not significantly affect the hydrocarbon degradation efficiency of the OS-100 consortium. To the contrary, hydrocarbon biodegradation dropped from 94.1 to 54.4% and 5% when the OS-100 consortium was deprived from phosphate and nitrogen sources in the culture medium, respectively. Quantitative PCR revealed that alkB gene expression increased up to the 3rd day of incubation with 11.277-fold, consistent with the observed increments in hydrocarbon degradation. Illumina-MiSeq sequencing of 16 S rRNA gene fragments revealed that the OS-100 consortium was mainly composed of the genera Halomonas, Idiomarina, Alcanivorax and Chromohalobacter. This community structure changed depending on the culturing conditions. However, remarkable changes in the community structure were not always associated with remarkable shifts in the hydrocarbonoclastic activity and vice versa. The results show that probably synergistic interactions between community members and different subpopulations of the OS-100 consortium contributed to salinity tolerance and hydrocarbon degradation.

Status, threats, and conservation considerations of selected marine habitats and organisms in the Arabian/Persian Gulf

Many studies indicated that marine habitats and organisms in the Arabian/Persian Gulf ('Gulf') are broadly deteriorating. However, this likely results from the generalization of a few declining habitats or organisms in some locations. Here, we conduct a review to evaluate the status of selected habitats (mangroves, seagrasses, and coral reefs) and organisms (exploited bony fish, sharks, rays, dolphins, whales, and dugongs) and identify major threats to them in each Gulf country (except Iraq and Oman). We show that out of 52 habitats and organisms in the six countries, the predominant status (63.5%) is "Data-deficient", followed by "Decline" (21.2%) and "Increase-stable" (15.4%). The major threats to these habitats and organisms are coastal development, desalination plants, climate change, and fishing. However, our findings differentiate that some of these threats are causing severe degradation (i.e., have "Observed" impacts) while other threats, such as desalination plants, have potential impacts that are derived from laboratory experiments or modelling work. Our results can be used to guide conservation efforts in the region.

Determination of potentially toxic elements bioaccumulated in the commercially important pelagic fish narrow-barred Spanish mackerel (Scomberomorus commerson)

Anthropogenic activities have increased the discharge of marine contaminants threatening marine life. Small gulfs, such as the Arabian Gulf, are vulnerable to accumulating potentially toxic elements in marine species due to slow water exchange. The concentration of 21 elements was determined in the tissues of Scomberomorus commerson from Umm Al Quwain (United Arab Emirates) and Bandar Abbas (Iran). Chromium, Copper, and Iron exceeded internationally established maximum permissible limits. Sites could not be distinguished based on Principle Component Analyses of elements. Elevated Cu and Cr in muscle are of concern to marine species as well as humans. Metal Pollution Index showed a significant difference between sites, with 20.34 % and 100 % of individuals suffering high metal toxicity and poor body conditions, respectively. The Arabian Gulf is experiencing an increase in discharge of industrial wastes. Implementation of strict policies to reduce discharge of toxic substances is required to protect marine organisms and humans.

Root-specific flavones and critical enzyme genes involved in their synthesis changes due to drought stress on Scutellaria baicalensis

Introduction

Scutellaria baicalensis is rich in bioactive flavonoid, which are widely used in clinical therapy. Many environmental factors, such as water and temperature, affect gene expression and secondary metabolites accumulation in plants.

Methods

In this study, to explore the effect of drought stress on the accumulation of flavonoids and gene expression in S. baicalensis seedlings, 4-week-old Scutellaria baicalensis seedlings were treated with different concentrations of PEG6000 to simulate drought stress. The contents of four root-specific flavones (baicalein, wogonin, baicalin, and wogonoside) in samples under different treatments were quantitatively analyzed by high performance liquid chromatography (HPLC). The expression levels of flavonoid biosynthesis-related genes (PAL1, PAL2, CHS, and UBGAT) were determined by real-time quantitative PCR (qRT-PCR). Also, a correlation analysis between flavonoid contents and gene expression levels was made.

Results

The HPLC results revealed that 5 and 10% PEG6000 treatments significantly increased the content of four flavonoids, with 5% PEG 6000 treatment being the most beneficial to the flavonoids accumulation. The qRT-PCR results showed that PAL2 and CHS gene expressions differed significantly in different organs, while PAL1 and UBGAT had poor organ-specific. For genes in roots, the expression of PAL1 and UBGAT was the highest in 5% PEG6000 treatment, and PAL2 and CHS were the highest in 10% PEG6000 treatment. Compared with other concentrations of PEG6000, 5 and 10% PEG6000 were more advantageous for gene expression. Collectively, PEG6000 at a low concentration promoted the accumulation of flavonoids and the expression of related genes. Additionally, the correlation results demonstrated that PAL1, PAL2, CHS, and UBGAT genes in roots stimulated the formation and accumulation of the four flavonoids to varying degrees, while the exception of PAL2 gene expression in roots was negatively correlated with wogonin content.

Discussion

This study for the first time investigated the effect of drought stress on the downstream gene UBGAT in S.baicalensis seedlings as well as the correlation between gene expression and flavonoid content in S. baicalensis seedlings under drought stress, providing a new sight for studying the effects of drought stress on flavonoid accumulation and related gene expression in S. baicalensis.