Recent and future trends in sea surface temperature across the Persian Gulf and Gulf of Oman

Mapping pollution dynamics: utilizing GNOME to model oil spill trajectories in tanker terminals

The aim of this study is to uncover the multifaceted environmental threats posed by Oil Spill Water Pollution (OSWP) originating from tanker terminals situated in the Qeshm and Hormozgan regions of Iran. In this region, water pollution arises from diverse sources, mostly from ruptured pipelines, corroded valves, unforeseen accidents, and aging facilities. The Qeshm Canal and Qeshm Tanker Terminal emerged as pivotal sites for investigation within this study. The focus is directed towards pinpointing vulnerable areas at risk of water contamination and delving into the intricate pathways and impacts associated with oil spills. Utilizing the sophisticated modeling capabilities of the National Oceanic and Atmospheric Administration's (NOAA) GNOME model, the research explores various scenarios extrapolated from seasonal atmospheric and oceanic data through 2022. The findings show the OSWP hazard zones located northeast of Qeshm. Notably, the wind and currents greatly affect how OSWPs are destined and dispersed. This underscores the intricate interplay between environmental factors and spill dynamics. In essence, this study not only sheds light on the imminent environmental threats posed by OSWP but also underscores the critical need for proactive measures and comprehensive strategies to mitigate the adverse impacts on marine ecosystems and coastal communities.

Biofouling and corrosion rate of welded Nickel Aluminium Bronze in natural and simulated seawater

Updated understanding on the effect of biofouling on corrosion rate is needed to protect marine structures as climate change is altering seawater physiochemistry and biofouling organism distribution. Multi-disciplinary techniques can improve understanding of biofouling development and associated corrosion rates on metals immersed in natural seawater (NSW). In this study, the development of biofouling and corrosion on welded Nickel Aluminium Bronze (NAB) was investigated through long-term immersion tests in NSW, simulated seawater (SSW) and air. Biofouling was affected by geographic location within the marina and influenced corrosion extent. The corrosion rate of NAB was accelerated in the initial months of exposure in NSW (1.27 mm.yr-1) and then settled to 0.11 mm.yr-1 (annual average). This was significantly higher than the 0.06 mm.yr-1 corrosion rate measured in SSW, which matched published rates. The results suggest that corrosion rates for cast NAB should be revised to take account of biofouling and updated seawater physiochemistry.

A new spatial estimation model and source apportionment of aliphatic hydrocarbons in coastal surface sediments of the Nayband Bay, Persian Gulf

Hydrocarbons, originating from oil and gas industries, are considered a potential risk for Nayband Bay, a natural marine park with extended mangroves, located on the north coastlines of the Persian Gulf, Iran. This paper determines the potential sources and spatial distribution of hydrocarbons, especially aliphatic hydrocarbons (AHCs), in Nayband Bay through the simultaneous application of three indices in the coastline surface sediments. To this end, a field study was conducted in the inter-tidal coastal zones and wetlands. Sediment samples were taken from surface layers along four transects with four sampling points at different distances from the gulf. The hydrocarbon compounds of the samples including AHCs, total petroleum hydrocarbons, and heavy metals (Ni, V as crude oil indicators) were analyzed and classified to discover the pollution indicators. Pearson pairwise correlation and cluster analyses along with pollution indices were employed to describe the spatial distribution pattern of hydrocarbons, identify hot spots, and determine the potential origin of AHCs. Different interpolation scenarios based on topographic and oceanic features were proposed to detect the spatial dynamics of AHCs. The results revealed that hydrocarbons mainly originated from anthropogenic sources including oil and gas industries located far from the affected area. It was also concluded that the long-distance pollution transfer was based on oceanic currents and wind direction in the bay. The proposed scenarios showed that the mean concentration values of total organic carbon and total organic material vary in the range 0.19 ppm to 0.4 ppm and 2.88 ppm to 3.20 ppm, respectively.

Thermal optima of cercarial emergence in trematodes from a marine high-temperature ecosystem, the Persian Gulf

Global warming may alter the dynamics of infectious diseases by affecting important steps in the transmission of pathogens and parasites. In trematode parasites, the emergence of cercarial stages from their hosts is temperature-dependent, being highest around a thermal optimum. If environmental temperatures exceed this optimum as a consequence of global warming, this may affect cercarial transmission. However, our knowledge of cercarial emergence patterns of species from high temperature environments is currently very limited. Here, we investigated the effect of temperature on the emergence of two common trematode species from an abundant mud snail Pirenella cingulata in the Persian Gulf, the warmest sea on Earth. Infected snails were incubated in the laboratory at 6 temperatures from 10 to 40 °C for 3 days. We found an optimal temperature for cercarial emergence of 32.0 °C and 33.5 °C for Acanthotrema tridactyla and Cyathocotylidae gen. sp., respectively, which are the warmest recorded thermal optima for any aquatic trematode species. Emergence of both species dropped at 40 °C, suggesting upper thermal limits to emergence. Overall, Persian Gulf trematodes may be among the most heat-tolerant marine trematode species, indicating a potential for dispersing to regions that will continue to warm in the future.

Spatiotemporal variability of the Persian Gulf and Oman Sea marine heatwaves during 1982-2020

For the first time, this study explored the dominant features of Marine HeatWaves (MHWs) in the Persian Gulf and Oman Sea (1982-2020). The spatial extent of MHWs has nearly doubled in the last 24 years. Since 1997, the average number of MHW days in the central parts of the Persian Gulf has increased about 19 times compared to the period 1982-1997. The average number of the detected MHW events has increased by about three times. Simultaneously with the increase in MHWs frequency trend, the trend in the average number of MHW days has also increased. Since 1997, the average number of MHW days in the study area has almost increased by 10 times. The mean duration of the detected MHWs ranged from 5 to10 days. On average, in a major part of the Persian Gulf, about 1-2 MHW events occur annually.

Mesozooplankton community in near-hypoxic and hypoxic layers of the Persian Gulf and the Gulf of Oman

To assess the role of near-hypoxic and hypoxic conditions on the mesozooplankton community, we studied twenty stations in the Persian Gulf and the Gulf of Oman. The physicochemical parameters were measured using a CTD probe and mesozooplankton were sampled vertically using a closing net. Results showed the hypoxic conditions of 0.52 ± 0.11, 1.40 ± 0.48, and 0.84 ± 0.08 in the lower layers in stations T11S3, T0S8B, and T9S5 in the Gulf of Oman and near-hypoxic conditions in station T6S3 (2.99 ± 0.05) in the Persian Gulf. The marginal test revealed that stratification during summer and dissolved oxygen and salinity during spring in the Persian Gulf and temperature, stratification, and dissolved oxygen during spring in the Gulf of Oman significantly explained the variation of mesozooplankton composition in the study areas (p < 0.05). The present study reveals some general patterns of mesozooplankton assemblage in near-hypoxic and hypoxic conditions, but a future detailed investigation will be essential.

Communities of culturable yeasts and yeast-like fungi in oligotrophic hypersaline coastal waters of the Arabian Gulf surrounding Qatar

This report is the first investigation of yeast biodiversity from the oligotrophic hypersaline coastal waters of the Arabian Gulf surrounding Qatar. Yeasts and yeast-like fungi, were cultured from seawater sampled at 13 coastal areas surrounding Qatar over a period of 2 years (December 2013-September 2015). Eight hundred and forty-two isolates belonging to 82 species representing two phyla viz., Ascomycota (23 genera) and Basidiomycota (16 genera) were identified by molecular sequencing. The results indicated that the coastal waters of the Qatari oligotrophic marine environment harbor a diverse pool of yeast species, most of which have been reported from terrestrial, clinical and aquatic sources in various parts of the world. Five species, i.e., Candida albicans, C. parapsilosis, C. tropicalis, Pichia kudriavzevii and Meyerozyma guilliermondii (n = 252/842; 30% isolates) are known as major opportunistic human pathogens. Fifteen species belonging to nine genera (n = 498/842; 59%) and 12 species belonging to seven genera (n = 459/842; 55%) are hydrocarbon degrading yeast and pollution indicator yeast species, respectively. Ascomycetous yeasts were predominant (66.38%; 559/842) as compared to their basidiomycetous counterparts (33.6%; 283/842). The most isolated yeast genera were Candida (28%; 236/842) (e.g., C. aaseri, C. boidinii, C. glabrata, C. intermedia, C. oleophila, C. orthopsilosis, C. palmioleophila, C. parapsilosis, C. pseudointermedia, C. rugopelliculosa, C. sake, C. tropicalis and C. zeylanoides), Rhodotorula (12.7%; 107/842), Naganishia (8.4%; 71/842), Aureobasidium (7.4%; 62/842), Pichia (7.3%; 62/842), and Debaryomyces (6.4%; 54/842). A total of eleven yeast species ( n = 38) isolated in this study are reported for the first time from the marine environment. Chemical testing demonstrated that seven out of the 13 sites had levels of total petroleum hydrocarbons (TPH) ranging from 200 to 900 µg/L, whereas 6 sites showed higher TPH levels (> 1000-21000 µg/L). The results suggest that the yeast community structure and density are impacted by various physico-chemical factors, namely total organic carbon, dissolved organic carbon and sulphur.

Baseline assessment of coral diseases in an environmentally extreme environment of the northern Persian Gulf

The coral diseases are recognized as serious threats to coral reef ecosystems and a major contributor to the reduction of zooxanthellate scleractinian populations worldwide. Quantitative disease surveys can provide important information on the status and trends of coral reef health over the time. In this study, coral disease surveys were carried out during August 2014 and 2015 at designated sites located in the northern Persian Gulf. Seven different diseases affecting eight scleractinian genera were documented: Black Band Disease (BBD), Skeletal Growth Anomaly (SGA), Arabian Yellow Band Disease (AYBD), White Mat Disease (WMD), White Syndrome (WS), Porites Pink Spot (PPS), and Porites Bleached Patches (PBP). Additionally, it should be noted that this is the first report of SGA in Acropora sp. found in the Persian Gulf. The results of this study generated a baseline dataset of various related diseases in the northern Persian Gulf which can be utilized for future studies.

Spatiotemporal Variability of Chlorophyll-a and Sea Surface Temperature, and Their Relationship with Bathymetry over the Coasts of UAE

The catastrophic implication of harmful algal bloom (HAB) events in the Arabian Gulf is a strong indication that the study of the spatiotemporal distribution of chlorophyll-a and its relationship with other variables is critical. This study analyzes the relationship between chlorophyll-a (Chl-a) and sea surface temperature (SST) and their trends in the Arabian Gulf and the Gulf of Oman along the United Arab Emirates coast. Additionally, the relationship between bathymetry and Chl-a and SST was examined. The MODIS Aqua product with a resolution of 1 × 1 km2 was employed for both chlorophyll-a and SST covering a timeframe from 2003 to 2019. The highest concentration of chlorophyll-a was seen in the Strait of Hormuz with an average of 2.8 mg m−3, which is 1.1 mg m−3 higher than the average for the entire study area. Three-quarters of the study area showed a significant correlation between the Chl-a and SST. The shallow (deep) areas showed a strong positive (negative) correlation between the Chl-a and SST. The results indicate the presence of trends for both variables across most of the study area. SST significantly increased in more than two-thirds of the study area in the summer with no significant trends detected in the winter.

Hypoxia in the Persian Gulf and the Strait of Hormuz

In this article dissolved oxygen results of research cruises through the Persian Gulf during 2018-2019 are discussed. The results showed that summer to autumn hypoxia occurred mainly at depths ≥ 50 m to the bottom. This seasonal hypoxia started in late summer reaching its greatest severity in mid-autumn with an area of 50,000 km² in the Persian Gulf. The minimum oxygen measured at the near-bottom layer of the western basin in autumn (25.8 μmol/kg) was lower than any previous measurement in the open waters of the Persian Gulf. In the Strait of Hormuz, the seasonal hypoxia appeared in summer in the near bottom of the most eastern part at the Iranian side. pH_T values recorded in hypoxic waters were as low as what is predicted for surface ocean under ocean acidification in 2100. Considering the results, we suggest evaluating the effects of hypoxia and acidification on the Persian Gulf ecosystems.

Influence of the mightiest rivers worldwide on coastal sea surface temperature warming

Ocean warming as a consequence of climate change occurred during the last decades is not homogeneous. This is especially patent for coastal areas, where the warming is influenced by local processes that occur at different time and spatial scales. In this sense, plumes formed by rivers discharge can play a key role in sea surface temperature (SST) warming. SST trends for the coastal points affected by the plumes of the 19 world's mightiest rivers (south 60°N) and their oceanic counterparts were analyzed by means of NOAA's AVHRR OISST data over the period 1982-2019. Coastal areas affected by river plumes showed an annual less intense warming trend than observed at the adjacent ocean in all cases. In average, warming trend was 0.088 °C dec^-1 lower for coastal areas, ranging from 0.027 °C dec^-1 for Mekong and Irrawaddy/Salween River plume systems to 0.208 °C dec^-1 and 0.278 °C dec^-1 for Mississippi and Paraná River plumes. The differences in coastal-ocean warming obtained for rivers debouching into inland seas (Danube and Volga Rivers) are similar to the ones observed for the rest of the rivers, even if inland seas are prone to higher warming rates than open seas. As the main conclusion, river plumes seem to have the ability to modulate SST warming near coast within the current context of global warming.

World record extreme sea surface temperatures in the northwestern Arabian/Persian Gulf verified by in situ measurements

The Arabian or Persian Gulf is recognized as one of the warmest estuaries globally. The sea surface temperature (SST) has been utilized in several studies to gauge the global warming associated with climate change. In the current investigation we present detailed in situ SST measurements for five consecutive years (2016, 2017, 2018, 2019, 2020) in the northwest of the Gulf, specifically in Kuwait Bay. Results of data analyses were compared with the historical records for the region, revealing that the SST reached an extreme level never previously recorded either in the Gulf. The extreme SST in Kuwait Bay reached 37.6 °C, recorded by the offshore station KISR01 located in the middle of the Bay. The event was associated with heatwave, neap tides, and an extended period of Kous winds which are characterized by high humidity levels and accompanied by large-scale intermittent fish kill incidents that extended the full length of the Kuwait coastline. Several fish kill incidents were reported also at the northern edge of the Gulf along Shatt Al Arab stretch in Iraq. The species found dead during the incident varied considerably, unlike those found in the frequent summer incidents. The records presented in this study may provide evidence to the effects of global warming, aid further research, and encourage the concerned international government bodies to deliver urgent environmental policies.

Freshwater budget in the Persian (Arabian) Gulf and exchanges at the Strait of Hormuz

Excess evaporation within the Persian (also referred as the Arabian) Gulf induces an inverse-estuary circulation. Surface waters are imported, via the Strait of Hormuz, while saltier waters are exported in the deeper layers. Using output of a 1/12-Degree horizontal resolution ocean general circulation model, the spatial structure and time variability of the circulation and the exchanges of volume and salt through the Strait of Hormuz are investigated in detail. The model’s circulation pattern in the Gulf is found to be in good agreement with observations and other studies based on numerical models. The mean export of salty waters in the bottom layer is of 0.26±0.05Sv (Sverdrup = 1.0 × 10⁶m³s⁻¹). The net freshwater import, the equivalent of the salt export divided by a reference salinity, done by the baroclinic circulation across that vertical section is decomposed in an overturning and a horizontal components, with mean values of 7.2±2.1 × 10⁻³Sv and 5.0±1.7 × 10⁻³Sv respectively. An important, novel finding of this work is that the horizontal component is confined to the deeper layers, mainly in the winter. It is also described for the first time that both components are correlated at the same level with the basin averaged evaporation minus precipitation (E-P) over the Persian Gulf. The highest correlation (r² = 0.59) of the total freshwater transport across 26°N with E-P over the Gulf is found with a one-month time lag, with E-P leading. The time series of freshwater import does not show any significant trend in the period from 1980 to 2015. Power spectra analysis shows that most of the energy is concentrated in the seasonal cycle. Some intraseasonal variability, likely related to the Shamal wind phenomenon, and possible impacts of El-Nino are also detected. These results suggest that the overturning and the horizontal components of freshwater exchange across the Strait of Hormuz are both driven by dynamic and thermodynamic processes inside the Persian Gulf.

Modern Benthic Foraminiferal Diversity: An Initial Insight into the Total Foraminiferal Diversity along the Kuwait Coastal Water

Kuwait territorial water hosts an important part of national biodiversity (i.e., zooplankton and phytoplankton), but very limited information exists on the overall diversity of benthic foraminifera. On the basis of the integration of publications, reports and theses with new available data from the Kuwait Bay and the northern islands, this study infers the total benthic foraminiferal diversity within Kuwait territorial water. This new literature survey documents the presence of 451 species belonging to 156 genera, 64 families, 31 superfamilies and 9 orders. These values are relatively high in consideration of the limited extension and the shallow depth of the Kuwait territorial water. Kuwait waters offer a variety of different environments and sub-environments (low salinity/muddy areas in the northern part, embayment, rocky tidal flats, coral reef systems, islands and shelf slope) that all together host largely diversified benthic foraminiferal communities. These figures are herein considered as underestimated because of the grouping of unassigned species due to the lack of reference collections and materials, as well as the neglection of the soft-shell monothalamids (‘allogromiids’).

Impact of warming on biofouling communities in the northern Persian Gulf

While the impact of ocean warming on single species is well described, the impact on marine biofouling communities is not well understood. Effluents of power plants have higher temperatures and can be used as natural large-scale test sites to investigate warming effects on marine ecosystems. In the present study, we evaluated the impact of elevated temperatures in the vicinity of a power plant on macro-biofouling communities in the northern coast of the Persian Gulf. The impact site was on average 2 °C warmer than the control site. Our results demonstrate a significantly different structure and composition of biofouling communities between control and impact sites. Warming led to a 1.5-fold increase in the mean coverage of biofouling communities and slightly decreased functional and species richness. Our results indicated that future warming will likely increase biofouling pressure, while decreasing diversity of communities, particularly in habitats where organisms exist at their upper tolerance limits of temperature.

An Assessment of the Accuracy of MODIS Land Surface Temperature over Egypt Using Ground-Based Measurements

Space-based data have provided important advances in understanding climate systems and processes in arid and semi-arid regions, which are hot-spot regions in terms of climate change and variability. This study assessed the performance of land surface temperatures (LSTs), retrieved from the Moderate-Resolution Imaging Spectroradiometer (MODIS) Aqua platform, over Egypt. Eight-day composites of daytime and nighttime LST data were aggregated and validated against near-surface seasonal and annual observational maximum and minimum air temperatures using data from 34 meteorological stations spanning the period from July 2002 to June 2015. A variety of accuracy metrics were employed to evaluate the performance of LST, including the bias, normalized root-mean-square error (nRMSE), Yule–Kendall (YK) skewness measure, and Spearman’s rho coefficient. The ability of LST to reproduce the seasonal cycle, anomalies, temporal variability, and the distribution of warm and cold tails of observational temperatures was also evaluated. Overall, the results indicate better performance of the nighttime LSTs compared to the daytime LSTs. Specifically, while nighttime LST tended to underestimate the minimum air temperature during winter, spring, and autumn on the order of −1.3, −1.2, and −1.4 °C, respectively, daytime LST markedly overestimated the maximum air temperature in all seasons, with values mostly above 5 °C. Importantly, the results indicate that the performance of LST over Egypt varies considerably as a function of season, lithology, and land use. LST performs better during transitional seasons (i.e., spring and autumn) compared to solstices (i.e., winter and summer). The varying interactions and feedbacks between the land surface and the atmosphere, especially the differences between sensible and latent heat fluxes, contribute largely to these seasonal variations. Spatially, LST performs better in areas with sandstone formations and quaternary sediments and, conversely, shows lower accuracy in regions with limestone, igneous, and metamorphic rocks. This behavior can be expected in hybrid arid and semi-arid regions like Egypt, where bare rocks contribute to the majority of the Egyptian territory, with a lack of vegetation cover. The low surface albedo of igneous and limestone rocks may explain the remarkable overestimation of daytime temperature in these regions, compared to the bright formations of higher surface albedo (i.e., sandy deserts and quaternary rocks). Overall, recalling the limited coverage of meteorological stations in Egypt, this study demonstrates that LST obtained from the MODIS product can be trustworthily employed as a surrogate for or a supplementary source to near-surface measurements, particularly for minimum air temperature. On the other hand, some bias correction techniques should be applied to daytime LSTs. In general, the fine space-based climatic information provided by MODIS LST can be used for a detailed spatial assessment of climate variability in Egypt, with important applications in several disciplines such as water resource management, hydrological modeling, agricultural management and planning, urban climate, biodiversity, and energy consumption, amongst others. Also, this study can contribute to a better understanding of the applications of remote sensing technology in assessing climatic feedbacks and interactions in arid and semi-arid regions, opening new avenues for developing innovative algorithms and applications specifically addressing issues related to these regions.