Spatial variability of summer hydrography in the central Arabian Gulf

The Arabian Gulf is a very significant ocean body, which hosts more than 55% of the oil reserves of the world and produces about 30% of the total production, and thus, it is likely to face high risk and adverse problems by the intensified environmental stressors and severe climatic changes. Therefore, understanding the hydrography of the Gulf is very essential to identify various marine environmental issues and subsequently, developing marine protection and management plans. In this study, hydrography data collected at 11 stations along 3 linear transects in the early summer of 2016 were analyzed. The physicochemical parameters exhibited apparent variations along each transect, both laterally and vertically, connected to stratification, formation of different water masses and excessive heating. The temperature and salinity decreased laterally from nearshore to offshore, while layered density structures were identified in the offshore regions. The pH, dissolved oxygen (DO) and chlorophyll fluorescence (Fo) exhibited distinct horizontal and vertical variations. The observed pH is within the normal ranges, indicating that seawater acidification may not be a threat. The highest DO (6.13–8.37 mg/l) was observed in a layer of 24-36 m water depth in the deeper regions of the central transect

Observed variability in physical and biogeochemical parameters in the central Arabian Gulf

In situ measurements of physical and biogeochemical variables were conducted along a transect in the Exclusive Economic Zone (EEZ) of Qatar during late summer (September 2014) and winter (January 2015) to investigate their vertical, spatial and temporal variability. The study reveals that the water column is characterized by strong stratification during late summer in the deepest station, where the water depth is around 65 m and the surface to bottom temperature variation is around 9.1°C. The water column is vertically homogeneous during winter due to surface cooling and wind mixing. The surface to 23 m water column is characterized by ample dissolved oxygen (DO) during late summer and winter in the offshore regions, however, relatively low DO is found during late summer due to weak mixing and advection under weak winds and currents. Dissolved oxygen drops to hypoxic levels below the summer thermocline, and the winter high DO layer extends up to the bottom. Chlorophyll-a (Chl-a) is relatively high during late summer in the offshore region, while that in the nearshore regions is very low, which is linked to the anthropogenic stresses from the central east coast of Qatar. The results identified in this study fill an essential gap in the knowledge of regional primary production dynamics.Environmental Science Center (ESC) & Department of Biological and Environmental Sciences (DBES), Qatar University (QU

Physical drivers of chlorophyll and nutrients variability in the Southern-Central Arabian Gulf

The southern-central Arabian Gulf demonstrates a poor understanding of nutrients and chlorophyll dynamics in physical-biogeochemical settings. Here, using data of chlorophyll, nutrients and hydrographic parameters collected in two cruises in summer 2019 and winter 2020, we examined variability in nutrients and chlorophyll concentrations, and the driving mechanisms. Summer thermal stratification enhanced by intrusion of fresher surface water plume from the Arabian Sea developed a hypoxic zone (DO  0.05). Photo-protective carotenoids content in summer (0.59 mg/m3) was about 2.7 times their winter concentration. Winter cooling resulted in downwelling of dense water on the shallow coastal banks, which enhanced near bottom oxygen concentrations and swept away nutrient-rich water resulting in lower winter chlorophyll. This research features aspects of the physical and biogeochemical drivers underpinning the dynamics of nutrients and chlorophyll in the central Gulf.This work was funded by QU Grant [QUST-2-CAS-2019-44]

Role of shamal and easterly winds on the wave characteristics off Qatar, central Arabian Gulf

Waves in the Arabian Gulf (Gulf) are dominated by shamal winds during winter and early summer. Although wave characteristics in the Gulf are broadly studied, features associated with various wind systems are not explicitly covered, especially in the Exclusive Economic Zone (EEZ) of Qatar. In this study, we analyzed the wave parameters measured off Fuwairit, north coast of Qatar during 29 October – 26 November 2019 to identify the features associated with different wind systems. The analyses have been further extended to the Gulf using the reanalysis waves obtained from the COPERNICUS Marine Environment Monitoring Services (CMEMS) to describe the monthly, seasonal and annual characteristics. Results indicate that Nashi winds influence the east and northeast coasts of Qatar with higher waves than those generated by shamal winds. We find exceptional easterly (Nashi) waves during March 2019 contributing to the highest monthly mean Hs, which is a deviation from the known long-term wave climate of the Gulf.This work was jointly carried out under the IRCC International Research Co-Fund Collaboration Program of QU and CSIR-NIO, executed through Office of Research Support (ORS), QU (IRCC-2019-002)

Wind energy potential along the onshore and offshore Qatar

Wind energy is one among the clean and renewable energy resources. The utilization of non-conventional energies over the conventional sources helps to reduce the carbon emissions significantly. The present study aims at investigating the wind energy potential at select coastal locations of Qatar using ERA5 winds. ERA5 is the updated reanalysis product of the European Centre for Medium-range Weather Forecasts (ECMWF), in which the scatterometer and in situ wind data are assimilated to improve the accuracy of predictions, thus the long-term and short-term variabilities are reasonably well captured. Compared to the earlier studies, in this work, we have assessed the wind power at inland and o?shore areas of Qatar, considering 40-year long (1979-2018) time series data with hourly ERA5 winds at 10-m height. The results show that there is no signi?cant increase or decrease of wind power around Qatar in the last 40 years in most of the locations, while there is a slight decreasing trend in the o?shore areas of Ruwais. This indicates that the average wind power is consistently available throughout the years. The links of climatic indices, especially the ENSO events with the wind climate of Qatar, are clearly evident in the long-term data. As obvious, the o?shore regions of Qatar have relatively high wind power compared to the land areas. Among the select locations, the highest annual mean wind power density is obtained in the o?shore Ruwais (152 W/m2), followed by o?shore Ras La?an (134 W/m2) and land area of Al Khor (120 W/m2). The maximum wind power density varies between 1830 and 2120 W/m2 in the land areas, while it is between 1850 and 2410 W/m2 in the o?shore areas of Qatar. The highest wind power is consistently available during the prevalence of shamal winds in winter (January-March) as well as summer (June)

Methylmercury bioaccumulation among different food chain levels in the EEZ of Qatar (Arabian Gulf)

Methylmercury (MeHg) concentrations in three different species from different trophic levels with different amounts of Hg exposures were determined for the first time in the EEZ of Qatar. Sampling was conducted during autumn 2017 in two nearshore (Palm Tree and Al-Besheriya Islands) and two offshore locations (Sherawoo and Ishat Islands). Fish muscle and liver tissues were analyzed according to the US Environmental Protection Agency Method 1630. The lowest mean MeHg concentration was found to be 42.3 ppb wet weight in the lower trophic level fish Gerres oyena due to small fish size and trophic level; whereas, the highest MeHg concentration was found in higher trophic level sharks Rhizoprionodon oligolinx and Chiloscyllium arabicum with mean wet weight concentrations of 712 ppb and 166 ppb, respectively. Linear relationships were found between fish body size (weight, length, age) and MeHg concentrations. MeHg bioaccumulation was found to be higher in liver than in muscle tissue; however, there was no significant difference in tissue MeHg accumulation as well as, the concentrations between the four locations. The present study concludes that MeHg in most of the fish tissues is within the allowable limits and pose no threat to public health. Only the higher trophic level shark Rhizoprionodon oligolinx was found to have a MeHg concentration higher than the US EPA advisory level of 0.3 ppm. However, consumers should still be encouraged to eat smaller sized younger fish from lower trophic levels, which would be safer than larger older species from higher trophic levels

The maxima in northerly wind speeds and wave heights over the Arabian Sea, the Arabian/Persian Gulf and the Red Sea derived from 40 years of ERA5 data

Recent studies point out the importance of northerly winds and waves in the Arabian Sea, especially those due to shamal and makran events in addition to the northeast monsoon system. We have analyzed climatology and trends of northerly maximum wind speed and significant wave height (Hs) in the Arabian Sea and the connected marginal seas, Arabian/Persian Gulf and the Red Sea, during non-monsoon season derived from 40 years of ERA5 wind and wave data, and estimated monthly, annual and decadal extreme climate and their trends. The study brings out an increasing trend in the northerly maximum wind speed (0.8–1.2 cm/s/year) and Hs (0.42–0.88 cm/year) in the southern and central Arabian Sea, which is consistent with the global trend in extreme wind speed and Hs. The northern Arabian Sea including the Sea of Oman exhibits significant decreasing trend in northerly maximum wind speed (− 1.4 cm/s/year) and Hs (− 0.67 cm/year), while the Gulf and the Red Sea exhibit sectorial contrasting trend, indicating the dominance of localized effects in modifying the regional climate. Distinct features identified in the climate and trends of northerly winds and waves are further discussed.The project is funded under the IRCC International Research Co-Fund Collaboration Program of QU and NIO, executed through ORS, QU (IRCC-2019-002)

Hypoxia in the central Arabian Gulf Exclusive Economic Zone (EEZ) of Qatar during summer season

Abstract One of the most fascinating and unexpected discoveries during the Qatar University Marine Expeditions to the marine Exclusive Economic Zone (EEZ) of Qatar in 2000–2001, was the detection of a hypoxic water layer in the central region of the Arabian Gulf in waters deeper than 50 m. Hypoxia was defined as the region where the concentration of dissolved oxygen was less than 2 mg L−1. This article presents the discovery of hypoxia in the Arabian Gulf, based on samples collected (mainly during evening or night time) from vertical profiles along transects of the EEZ of Qatar and analyzed for physico-chemical properties, nutrients and chlorophyll-a. Hypoxia occurred in the summer months caused by an interaction between physical stratification of the water column that prevents oxygen replenishment, and biological respiration that consumes oxygen. Strong south-westerly winds (the SW monsoon) from June to September drive the relatively low-salinity nutrient-rich surface water from the Arabian Sea/Arabian Gulf (Sea of Oman) through the Strait of Hormuz into the central-Arabian Gulf, and this surface current penetration fertilizes the deep central-Arabian Gulf during the summer period. A strong seasonal pycnocline is formed between deeper waters at an ambient temperature of 20.9 °C and surface waters at 31.9 °C. This prevents the mixing of supersaturated O2 (>100–130%) water from the upper layer that would otherwise raise concentrations of dissolved oxygen below the thermocline, thus resulting in deep water hypoxia, i.e. dissolved oxygen levels of less than 0.86 ml L−1 at 17.3% saturation. These are the lowest values ever recorded for the Arabian Gulf.The calculated area of hypoxia is around 7220 square kilometers, and occurs in a layer about ≥15 m thick above the sea floor which extends toward the deep part of the Qatar Exclusive Economic Zone (EEZ). The biological consequences of this hypoxia on the sea floor are yet to be investigated

Mercury accumulation in Lethrinus nebulosus from the marine waters of the Qatar EEZ

Total mercury (THg) and methylmercury (MeHg) were recorded in the commercial demersal fish Lethrinus nebulosus, caught from six locations in Qatar EEZ (Exclusive Economic Zone). Concentrations of THg decreased in the order: liver ˃ muscle ˃ gonad. THg concentrations in fish tissue ranged from 0.016 ppm in gonad to 0.855 ppm (mg kg−1 w/w) in liver tissues, while concentrations in muscle tissue ranged from 0.24 to 0.49 ppm (mg kg−1 w/w) among sampling sites. MeHg concentrations were used to validate food web transfer rate calculations. Intake rates were calculated to assess the potential health impact of the fish consumption. There is no major threat to human health from the presence of Hg in L. nebulosus, based upon reasonable consumption patterns, limited to no more than three meals of L. nebulosus per week.Qatar National Research Fund (QNRF) under the National Priorities Research Program (NPRP) award number NPRP 09-505-1-08