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This baseline study highlights the 210Po and 210Pb concentration in seven macroalgae species from the northern Gulf that are frequently washed ashore during the bloom season from February to April. The highest concentrations of 210Po and 210Pb were 2.947 ± 0.032 and 1.057 ± 0.145 Bq kg−1 wwt, respectively, in brown algae Sargassum boveanum, and the lowest in green algae Ulva prolifera with 1.533 ± 0.058 and 0.170 ± 0.069 Bq kg−1 wwt, respectively. A 210Po enrichment was observed in both brown and green algae species , with the 210Po/210Pb ratio being >1 for all the samples. The mean concentration of 210Po in all species was an order of magnitude higher than 210Pb, and the difference in mean concentration is statistically significant (p < 0.001). At the same time, the mean concentration of dissolved 210Po and 210Pb in seawater was 0.28 ± 0.01 and 0.52 ± 0.01Bq m−3 with a 210Po/210Pb ratio of 0.54 ± 0.02 indicating that 210Po was absorbed from water and more concentrated by macroalgae. The measured concentration factor (CF) for 210Po in these macroalgae for the northern Gulf varied between 5 × 103–1 × 104, higher than the IAEA recommended value of 1 × 103 which suggests that a revision of that value may be needed. The field derived CFs for 210Pb vary between 3 × 102–1.8 × 103, comparable to the ICRP recommended value of 2 × 103. • This paper establishes the baseline for 210Po and 210Pb in macroalgae from northern Gulf. • Brown algae has higher 210Po and 210Pb concentration than green algae. • Difference in 210Pb and 210Po concentrations in seven macroalgae was statistically significant. • The concentration factor in both green and brown macroalgae is higher than IAEA recommended value. [ABSTRACT FROM AUTHOR]

Marine phytoplankton is a primary producer in the ocean that forms the base of the marine food web and supports the pelagic food chain. The two dominant groups of phytoplankton observed in northern Gulf waters are diatoms and dinoflagellates. The diatoms outnumber dinoflagellates in the Gulf waters. This study presents baseline information on the concentration of 210 Po among selected phytoplankton in the northern Gulf. The concentration among diatoms varies between 6.99 and 11.4 Bq kg −1 wwt, whereas a higher concentration range of 8.51–15.41 Bq kg −1 wwt was observed among dinoflagellates. The diatoms analyzed includes Thalassiosira spp. – 10.2–11.4 Bq kg −1 wwt; Chaetoceros spp. – 6.99–7.14 Bq kg −1 wwt; Rhizosolenia spp. – 9.12–9.95 Bq kg −1 wwt. The analyzed dinoflagellate genera include Gymnodinium spp. – 8.51–8.78 Bq kg −1 wwt; Noctiluca spp. – 15.2–15.4 Bq kg −1 wwt; and Karenia spp. – 14.1–14.9 Bq kg −1 wwt. The 210 Po concentration in seawater shows a seasonal variation, with a higher concentration range of 0.70 and 0.58 mBq L −1 during summer and autumn, whereas a lower range in concentration of 0.38 and 0.30 mBq L −1 occurring during winter and spring. The resultant computed concentration factors vary between 2 ∗ 10 4 –5 ∗ 10 4 demonstrating a significant 210 Po enrichment in the base of the pelagic food chain. [ABSTRACT FROM AUTHOR]

Kuwaiti territorial waters of the northwest Arabian Gulf represent a unique aquatic ecosystem prone to various environmental and anthropogenic stressors that pose significant constraints on the resident biota which must withstand extreme temperatures, salinity levels, and reducing conditions, among other factors to survive. Such conditions create the ideal environment for investigations into novel functional genetic adaptations of resident organisms. Firstly, however, it is essential to identify said organisms and understand the dynamic nature of their existence. Thus, this study provides the first comprehensive analysis of bacterial and archaeal community structures in the unique waters of Kuwait located in the Northwest Arabian Gulf and analyzes their variations with respect to depth, season, and location, as well as their susceptibility to changes in abundance with respect to various physicochemical parameters. Importantly, this study is the first of its kind to utilize a shotgun metagenomics approach with sequencing performed at an average depth of 15 million paired end reads per sample, which allows for species-level community profiling and sets the framework for future functional genomic investigations. Results showed an approximately even abundance of both archaeal (42.9%) and bacterial (57.1%) communities, but significantly greater diversity among the bacterial population, which predominantly consisted of members of the Proteobacteria, Cyanobacteria, and Bacteroidetes phyla in decreasing order of abundance. Little to no significant variations as assessed by various metrics including alpha and beta diversity analyses were observed in the abundance of archaeal and bacterial populations with respect to depth down the water column. Furthermore, although variations in differential abundance of key genera were detected at each of the three sampling locations, measurements of species richness and evenness revealed negligible variation (ANOVA p<0.05) and only a moderately defined community structure (ANOSIM r2 = 0.243; p>0.001) between the various locations. Interestingly, abundance of archaeal community members showed a significant increase (log2 median ratio of RA = 2.6) while the bacterial population showed a significant decrease (log2 median ratio = -1.29) in the winter season. These findings were supported by alpha and beta diversity analyses as well (ANOSIM r2 = 0.253; p>0.01). Overall, this study provides the first in-depth analysis of both bacterial and archaeal community structures developed using a shotgun metagenomic approach in the waters of the Northwest Arabian Gulf thus providing a framework for future investigations of functional genetic adaptations developed by resident biota attempting to survive in the uniquely extreme conditions to which they are exposed. [ABSTRACT FROM AUTHOR]

The ubiquitous nature of microplastics (MPs) in nature and the risks they pose on the environment and human health have led to an increased research interest in the topic. Despite being an area of high plastic production and consumption, studies on MPs in the Middle East and North Africa (MENA) region have been limited. However, the region witnessed a research surge in 2021 attributed to the COVID-19 pandemic. In this review, a total of 97 studies were analyzed based on their environmental compartments (marine, freshwater, air, and terrestrial) and matrices (sediments, water columns, biota, soil, etc.). Then, the MP concentrations and polymer types were utilized to conduct a risk assessment to provide a critical analysis of the data. The highest MP concentrations recorded in the marine water column and sediments were in the Mediterranean Sea in Tunisia with 400 items/m3 and 7960 items/kg of sediments, respectively. The number of MPs in biota ranged between 0 and 7525 per individual across all the aquatic compartments. For the air compartment, a school classroom had 56,000 items/g of dust in Iran due to the confined space. Very high risks in the sediment samples (Eri > 1500) were recorded in the Caspian Sea and Arab/Persian Gulf due to their closed or semi-closed nature that promotes sedimentation. The risk factors obtained are sensitive to the reference concentration which calls for the development of more reliable risk assessment approaches. Finally, more studies are needed in understudied MENA environmental compartments such as groundwater, deserts, and estuaries. [ABSTRACT FROM AUTHOR]

The dinoflagellates of the genus Gambierdiscus are found in almost all oceans and seas between the coordinates 35° N and 35° S. Gambierdiscus and Fukuyoa are producers of ciguatoxins (CTXs), which are known to cause foodborne disease associated with contaminated seafood. The occurrence and effects of CTXs are well described in the Pacific and the Caribbean. However, historically, their properties and presence have been poorly documented in the Indian Ocean (including the Bay of Bengal, Andaman Sea, and the Gulf). A higher occurrence of these microorganisms will proportionately increase the likelihood of CTXs entering the food chain, posing a severe threat to human seafood consumers. Therefore, comprehensive research strategies are critically important for developing effective monitoring and risk assessments of this emerging threat in the Indian Ocean. This review presents the available literature on ciguatera occurrence in the region and its adjacent marginal waters: aiming to identify the data gaps and vectors. [ABSTRACT FROM AUTHOR]