The recent trend of global warming has exerted a disproportionately strong influence on the Eurasian land surface, causing a steady decline in snow cover extent over the Himalayan-tibetan plateau region. Here we show that this loss of snow is undermining winter convective mixing and causing stratification of the upper layer of the Arabian Sea at a much faster rate than predicted by global climate models. over the past four decades, the Arabian Sea has also experienced a profound loss of inorganic nitrate. in all probability, this is due to increased denitrification caused by the expansion of the permanent oxygen minimum zone and consequent changes in nutrient stoichiometries. these exceptional changes appear to be creating a niche particularly favorable to the mixotroph, Noctiluca scintillans which has recently replaced diatoms as the dominant winter, bloom forming organism. Although Noctiluca blooms are non-toxic, they can cause fish mortality by exacerbating oxygen deficiency and ammonification of seawater. As a consequence, their continued range expansion represents a significant and growing threat for regional fisheries and the welfare of coastal populations dependent on the Arabian Sea for sustenance. The Arabian Sea (AS) is a unique, low-latitude oceanic ecosystem because it is influenced by monsoonal winds that reverse their direction seasonally 1. These reversing winds cause dynamic shifts in surface currents and alterations in the pycnocline, which help fertilize its normally nutrient-depleted surface layers. However, the mechanisms that drive water-column mixing, the upward transport of nutrients and the consequent upsurge of phytoplankton biomass during the summer (Jun.-Sep.) and the winter (Nov.-Feb.) monsoons are different 2-6. During the summer monsoon, nutrient enrichment is via coastal upwelling, which begins when the adjacent land mass becomes warmer relative to the AS, and low pressure develops over the Arabian Peninsula 3,7,8. During this time of the year, strong topographically-steered southwesterly winds blowing over the AS form a low-level atmospheric jet called the Findlater Jet 9. This jet induces a northeastwardly flow of the surface currents, leading to strong upwelling of deep, nutrient-rich waters, causing large phytoplankton blooms along the coasts of Somalia, Yemen, and Oman 3,5,6,10,11. In contrast, during winter, when the Eurasian continent cools, nutrient enrichment is via deep penetrative convective mixing as a result of excessive heat loss from the AS surface layer caused by cold and dry northeasterly winds blowing from the snow-covered Himalayan-Tibetan Plateau (HTP) 4,5. The erosion of the thermocline, and entrainment of deep (100-150 m) nutrient-rich waters into the surface layer of the AS, begins as early as Dec., and has a major influence on winter phytoplankton blooms observable as far south as 14°N 4,11,12 .

SUMMARY:Aphanius dispar (Rüppell, 1829) is a common marine-euryhaline teleost fish in the Near East that has undergone considerable intraspecific differentiation. Otolith morphology is used to analyse the diversity within A. dispar in the Gulf of Oman (Sea of Oman) and the Persian Gulf. A total of 134 individuals from lagoons and inland habitats of Oman, the United Arab Emirates and southern Iran are analysed. The results revealed that otolith traits that are under genetic control are strikingly different from those that are under the influence of environmental factors. A clear spatial structure of the populations is detectable, suggesting that the environmental flexibility of A. dispar, vicariance events during the last glacial maximum (21000-18000 BP), dispersal in the course of the Early Holocene sea-level rise, and Holocene to presentday interruption of gene flow at the Strait of Hormuz have shaped the intraspecific differentiation of A. dispar. These factors may also be responsible for diversification within other marine-euryhaline fishes in the Near East and Mediterranean Sea, and thus the findings can contribute to successful conservation management.

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The first record of the southern ocean sunfish Mola ramsayi in Omani waters is reported based on a single 916 mm total length specimen found stranded on the coasts of Sur City 193 km south of the Omani capital Muscat, 22835 ′ 10.22 ′′ N 59830 ′ 18.91 ′′ E. This account also represents the third northernmost record of a south ocean sunfish in the Indian Ocean. Morphometric and meristic data are provided and compared with those of 5 specimens caught off United Arab Emirates, Brazil and India. The southern ocean distribution of M. ramsayi is corrected in this report.

The marine ecosystem has been a key resource for secondary metabolites with promising biological roles. In the current study, bioassay-guided phytochemical investigations were carried out to assess the presence of enzyme inhibitory chemical constituents from the methanolic extract of marine green alga—Codium dwarkense. The bioactive fractions were further subjected to chromatographic separations, which resulted in the isolation of a new triterpenic acid; dwarkenoic acid (1) and the known sterols; androst-5-en-3β-ol (2), stigmasta-5,25-dien-3β,7α-diol (3), ergosta-5,25-dien-3β-ol (4), 7-hydroxystigmasta-4,25-dien-3-one-7-O-β-d-fucopyranoside (5), 7-hydroxystigmasta-4,25-dien-3-one (6), and stigmasta-5,25-dien-3β-ol (7). The structure elucidation of the new compound was carried out by combined mass spectrometry and 1D (1H and 13C) and 2D (HSQC, HMBC, COSY, and NOESY) NMR spectroscopic data. The sub-fractions and pure constituents were assayed for enzymatic inhibition of alpha-glucosidase. Compound 1 showed significant inhibition at all concentrations. Compounds 2, 3, 5, and 7 exhibited a dose-dependent response, whereas compounds 4–6 showed moderate inhibition. Utilizing such marine-derived biological resources could lead to drug discoveries related to anti-diabetics.