Abnormal growth patterns in the sea urchin Tripneustes CF. Gratilla (L.) under pollution (Echinodermata, Echinoidea)

The externae of parasitic sacculind, Sacculina leptodiae (Sacculindae: Rhizocephala: Cirripedia) on the xanthid crab, Leptodius exaratus (Xanthidae: Brachyura) were recorded during this study. A total of 691 individuals (400 males and 291 females) of this crab were collected from the intertidal coasts of the Egyptian Red Sea, Gulf of Suez and Gulf of Aqaba, of them 38 (23 males and 15 females) were infected with this parasite. The overall infection rate recorded 5.50% for all populations and was slightly higher in males (5.75%) than in females (5.15%). It showed seasonal, spatial and sex variations, recorded the highest rate (7.91%) at Gulf of Suez, declined sharply to 3.85 % at Gulf of Aqaba, and 2.43 % at all populations of the Red Sea, recorded the minimum rate of 0.57% at the southern populations. Autumn has the highest rate (10.34 %) at Hurghada (northern Red Sea), followed by summer with 9.34 % and 7.69 % at the Gulf of Suez and Ras Mohammed (Northern Red Sea), respectively, declined to 2.94 % in summer at Gulf of Aqaba, but increased again to 5.56% during spring. A total of 41 externae were recorded on the infected individuals, comprised 35 individuals with single externa (92.11 %), and only three with double externe (7.89 %). The highest number of externae was 13 (31.70 %) occurred on the 6th abdominal segment, followed by 11 (26.82 %) on the 5th segments, declined to 1-5 on the other segments except the first. The size of externae varied from 1.0 to 10.4 mm in breadth, averaged 5.19± 2.76 mm in males and 5.63± 3.17 mm in females. The rootlets of internae of the parasite invaded ovaries, testes, hepatopancreas, and all spaces within the crab body cavities. The disappearance or destruction of testes in infected males accompanied by remarkable broadness and segmentation of abdomens fringed with dense and length setae lead to “Parasitic castration”, compared with a hyperfiminzation in infected females due to the destruction of undeveloped ovaries and increasing abdominal setae dense and length.

The Red Sea, Gulf of Suez, and Gulf of Aqaba comprise the active plate boundaries that separate Africa-Nubia, Arabia and Sinai. This tripartite configuration has been in existence since the Middle Miocene, or about the past 12–14 Ma. We describe the ongoing and geologically recent tectonics of these regions. The Red Sea rift lies east of a broad region of E-W maximum horizontal stress (SHmax) that covers much of central Africa-Nubia. On its Arabian side, SHmax is oriented N-S to NE-SW. These far field stresses owe their origins to the spreading centres of the Atlantic Ocean and collision between Arabia and Eurasia along the Bitlis-Zagros suture. At the continental scale, the Red Sea is therefore subjected to compression perpendicular to or at a high-angle to its margins. The realm of shallow crustal stresses conducive to extensional faulting in a Red Sea orientation (rift-normal Shmin) is presently restricted to the Red Sea marine basin itself, and perhaps narrow belts along its shoulders. In the Gulf of Suez there is enough data to show that each of its sub-basins is presently undergoing extension, but in conjunction with differently oriented, sub-regional shallow crustal stress fields. These appear to be spatially related to the original Early Miocene syn-rift basin geometries. NNE-SSW extension in the southern Gulf of Suez is probably generated by sinistral slip on the similarly oriented Gulf of Aqaba transform margin. Large M > 6 earthquakes are generally restricted to the central basin of the Gulf of Aqaba, the southern Gulf of Suez, and the greater Afar region. The geodynamic details responsible for the focusing of these large events are specific to each locale but all are in general associated with the junctions of major plate boundaries. Catalogues of earthquake activity and GPS datasets show that the Sinai micro-plate is still moving away from Africa with a component of left-lateral slip. This results in components of extension perpendicular to both the Gulf of Suez and the Gulf of Aqaba. The kinematics of the southern Red Sea are similarly complex. Not all opening has jumped to the west side of the Danakil horst and significant tectonic activity still occurs along the southernmost Red Sea axis in the vicinity of the Zubair Archipelago. This is the only volcanically active segment of the Red Sea basin that is above sea level. Dike intrusions are ~N-S and not aligned parallel to the rift axis and may indicate that the underlying magmatism is swinging to the west to link with the Afar triple junction. All of the margins of the Red Sea, Gulf of Suez and Gulf of Aqaba underwent tectonically-driven rift shoulder uplift and denudation in the past, particularly during the main phases of continental rifting. However, during the past 125 kyr uplift has been focused along the footwalls of a few, active extensional faults. These include the Hammam Faraun-Tanka fault in the central Gulf of Suez, the Gebel el Zeit-Shadwan Island fault in the southern Gulf of Suez, the Sinai and Arabia coastal boundaries of the Gulf of Aqaba, and faults at Tiran Island at the junction of the Gulf of Aqaba and northern Red Sea. Smaller-scale extensional faulting is also occurring along the Saudi Arabian margin of the northern Red Sea, in the Dahlak and Farasan Archipelagos, and on the volcanically active islands of the Zubair Archipelago in the southernmost Red Sea. On the Farasan and Dahlak islands this is largely related to the movement of underlying salt bodies, similar to effects documented along the coastal plain of Yemen. Though not active at the present time, a broad belt of small-offset, very linear extensional faults dissected the western margin of the central Gulf of Suez during the Plio-Pleistocene. Similar age and style deformation has not been identified in the Suez sub-basins to the north or south. The most significant large-scale neotectonic features of the Red Sea rift system are its southern oceanic spreading centre and the northern linkage to the left-lateral Gulf of Aqaba—Levant transform fault. However, many segments of the rift margins and in particular the Gulf of Suez remain tectonically active. These areas provide stress field and horizontal and vertical displacement data that are relatively inexpensive to acquire and complementary to analyses of the offshore main plate boundaries themselves.

Analysis of SST and Chl-a data from MODIS-Aqua in the Major Egyptian Fishing Zones of the Red Sea

The Red Sea is characterised by a unique composition of species of fishes which, based on unpublished data of the present authors, currently consists of 1166 species from 159 families whose habitats range from shallow waters to the deep sea. There is a total of 1120 species in coastal waters of the Red Sea recorded within an overall depth range 0–200 m; among them, 165 species are exclusively endemics to the Red Sea, whilst another 51 species are restricted to the Red Sea and Gulf of Aden only, and 22 species living at depths greater than 200 m are endemic. As the westernmost peripheral area of the Indo-West Pacific region, the Red Sea is at the opposite end of the distributions of many widespread coral reef organisms that range to the easternmost regions, such as the Hawaiian Islands, Easter Island, and the Marquesas Islands. It is noted that these areas exhibit high percentages of endemism among coastal fishes. The Hawaiian archipelago has 30.7% of its fishes as endemic species; Easter Island has 21.7%, the Red Sea 14.7% (19.3% when combined with the Gulf of Aden), and the Marquesas Islands have 13.7% endemic fishes. The Red Sea is 2250 km in length and it is very deep, with an average depth of 490 m, and a maximum depth of 3040 m. As expected, the fish fauna is far from homogeneous. The most divergent sector is the Gulf of Aqaba. We have noted that its entrance to the rest of the Red Sea is shallow. It has a maximum width of only 24 km, but a maximum depth of 1850 m. The shore drops off quickly to deep water. The prevailing cross wind creates upwelling, resulting in surface sea temperature at least as low as 21 ℃. Twenty-two of 46 species of Red Sea fishes living at depths greater than 200 m in the Red Sea are endemic (48% endemism). The Gulf of Aqaba has 22 endemic coastal species of fishes and eight endemic deep-dwelling species. By contrast, the neighboring Gulf of Suez, with extensive sand flats and a maximum depth of 70 m, has only seven endemic species of fishes. Of the 165 endemic Red Sea species of fishes, only two are elasmobranchs. Twenty-three families of Red Sea fishes have more than 20% of endemic species with the highest rates of endemism occurring among the Pseudochromidae, Schindleriidae (83.3% and 100% respectively) and the family Gobiidae with the greatest number of endemic species (36 of 139 recorded species). A brief summary of the history of scientific research on Red Sea fishes is provided together with complete lists of endemic species for (i) the entire Red Sea (separately for coastal and deep-dwelling fishes); (ii) the Red Sea combined with the Gulf of Aden; (iii) the Gulf of Aqaba and the Gulf of Suez; and (iv) Lessepsian migrants. Ongoing research is likely to reveal additional endemic species in the region.

By the end of 2005 the global installed capacity for desalination of seawater was about 24.5·106 m3/day. The geographical distribution of the desalination plants was as follows: 77 % in the Middle East and North Africa, 10 % in Europe, 7 % in the Americas and 6 % in the Asia-Pacific region. The volume of brine discharged in the Red Sea increased from 6.4 million m3/day (in 1996) to 6.8 million m3/day (in 2008) and is still increasing due to the observed tendency to improve the average recovery ratio from 30 to 50 %. This will make the environmental concerns much more important in the future. There are two main sources of problems, i.e. the concentrate and chemical discharges and the cooling water effluent discharges. The salinity is expected to increase in the long term if larger and larger amounts of desalinated water are removed from the water bodies. A proper solution for the desalination waste brine disposal process requires a good balance between technical constraints (i.e. placing a pipe on the sea-bottom), environmental conditions (i.e., finding an optimum distance from the seashore where high salinity brine should be discharged without significant environmental impact; also, the availability for long run of brine disposal placement should be considered) and as low as possible overall economic costs.Since the potential cumulative impacts of desalination activity on the marine environment is expected to be more significant in case of regional seas, in this chapter we focus on the desalination plants in Red Sea. The objective is to discuss a modeling framework for the environmental-hydraulic design of the outfall system for desalination plants. The chapter presents an interdisciplinary combination of environmental issues with physical processes and discharge modeling. We assess the technical viability of disposal the brine effluent produced by desalination plants into Red Sea coastal regions via submarine pipes.There are several approaches to mitigate the environmental effects of the brine discharges. By tradition, the brine is discharged back to the sea in open channels. Impacts from high salinity may be avoided by pre-dilution of the desalination plant rejected stream with other waste streams, such as power plant cooling water. Impacts from high temperature may be avoided by ensuring heat dissipation from the waste stream to the atmosphere before entering the water body. However, simulations models for the brine plume dispersion from desalination power plants reveal the inadequacy of using surface discharging outfalls in order to brine discharging. Large capacity plants require submerged discharges which ensure a high dilution, reducing the harmful impacts on the marine environment. Mixing and dispersal of the discharge plume can be enhanced by installing a diffuser system, and by locating the discharge in a favorable oceanographic site which dissipates the heat and salinity load quickly.The central concept of the brine disposal by submerged pipes is the available head at the discharge point. Higher values of the available head ensure larger jet dispersion lengths and better conditions for ejected brine dilution. We have shown that the quality of the dilution process is well quantified by the Froude number of the brine discharge jet, whose optimum values range between 20 and 25. Using the Froude number allowed us to find the optimum pipe length and the optimum depth of the discharge point.About half of the Red Sea desalination plants are based on reverse osmosis. The percentage of RO plants is expected to increase, taking into account the lower production costs and the favorable technological evolution. The most representative RO desalination plants around the Red Sea coast are considered both by country and by capacity points of view. In order to provide relevant conclusions for the study reduced capacity desalination plants were selected due to their large number. For not available/existing desalination plants some hypothetic “case studies” were considered.Optimum brine dispersion may be obtained by using underwater pipes for any sort of high capacity and low capacity RO desalination plants operating on the Red Sea coasts. In case of large capacities, a pipe length around lX = 1,000 m allows optimum operation. A pipe length about lX = 500 m is needed for low capacity RO desalination plants.KeywordsFroude NumberReverse OsmosisDischarge PointDesalination PlantPipe LengthThese keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.

Seasonal flux patterns of planktonic foraminifera in a deep, oligotrophic, marginal sea: Sediment trap time series from the Gulf of Aqaba, northern Red Sea

BackgroundEchinometra mathaei (family Echinometridae), is one of the sea urchins widely distributed on the Egyptian coasts in the Red Sea. This organism contains edible and non-edible parts. The present study was carried out to analyze and identify the metabolites present in the non-edible parts (Aristotle's lantern and viscera) using LC/MS. Also, the cytotoxic activity on Vero cell line and antiviral activity against herpes simplex virus type 1 were evaluated using MTT colorimetric assay.ResultsChemical profiling of the crude extracts of Aristotle's lantern and viscera using LC/MS indicated the presence of 51 and 59 compounds, respectively. The main metabolites present in both non-edible parts were phospholipids, amino acids, peptides, fatty acids and glycerol derivatives. However, the characteristic difference was the presence of carotenoid pigments only in viscera. The crude extract of Aristotle's lantern and viscera showed no cytotoxic activity on Vero cell line and significant antiviral activity against herpes simplex virus with an IC50 value equal to 115.48 ± 1.20 and 122.4 ± 0.50 µg/mL, respectively.ConclusionsIn the present study, the crude extracts of the non-edible parts of E. mathaei were analyzed using LC.MS.MS.QTOF and indicated the existence of 110 chemical compounds, with significant antiviral activity against HSV-1 and no cytotoxic activity. The diversity of the identified compounds with two main categories of compounds, phospholipids and peptides, may contribute to the antiviral activity of Aristotle's lantern and viscera. Additionally, this research focused on clarification of nutritive, pharmaceutical and economic values of these parts. As future prospects, further studies are required to isolate the metabolites and assess the detailed mechanism of antiviral activity via in vitro, in vivo and in silico studies.

Gulfs of Suez and Aqaba: New insights from recent satellite-marine potential field data

Evaluating the impact of atmospheric deposition on dissolved trace-metals in the Gulf of Aqaba, Red Sea

Tourism development and desalination systems: Comparative analysis of systems' suitability for coastal areas of the Red Sea and Gulf of Aqaba, Egypt

The Sedentaria were from two similar habitats in the Gulf of Elat and the Mediterranean coast of Israel. These were porous rocks of Dendropoma spp. tubes encrusted on the seaward margins of intertidal platforms. The Sabellidae and Serpulidae have been treated elsewhere. Eleven remaining families, less abundant, are discussed here: Spionidae, Cirratulidae, Orbiniidae, Opheliidae, Arenicolidae, Capitellidae and Terebellidae (both habitats); Maldanidae and Sabellariidae (Mediterranean habitat); and Scalibregmidae and Chaetopteridae (Gulf of Elat). Of 15 species from the Mediterranean habitat, 12 are new records, while of 11 Gulf of Elat species, eight are new records for the Gulf of Elat and for the Red Sea. Branchiomaldane cf. vincenti, a new record in both habitats, is particularly abundant in the Mediterranean habitat. Mesochaetopterus crypticus n. sp., Ctenodrilus paucidentatus n. sp., and Zeppelina nova n. sp., are described from the Gulf of Elat habitat and Mediomastus cirripes n. sp. from the...

Geological Evolution of the Red Sea: Historical Background, Review, and Synthesis

The Gulf of Aqaba is located in the sub-tropical arid zone between 28o–29o30′N and 34o30′–35oE. It is a semi-enclosed basin that extends over a length of 180 km with a width between 5 and 25 km (average of 16 km). The deepest point in the Gulf reaches 1825 m with an average depth of 800 m. The Gulf is connected to the Red Sea by the Strait of Tiran, which has a sill depth of about 265 m. The Gulf exhibits a seasonal cycle of stratification in spring, maintenance of a shallow thermocline in summer, and subsequent deepening of the thermocline to produce deep mixed layers in winter. Much of the seasonal stratification variability is determined by exchanges with the rest of the Red Sea. Nonetheless, inter-annual variability in wintertime temperatures appears to set the depth of maximum mixing. Because of being generally warm (>21 oC), and subject to dry winds much of the year, the Gulf is a site of high evaporation rates, estimated at 0.5–1.0 cm/day, with recent estimated values lower than earlier ones. Given a surface area of the Gulf of about 1.7 × 109 m2, this implies a net inflow to the Gulf of about 54 m3s−1. Because the densities of the Gulf are different from the rest of the Red Sea, there are strong density-driven flows. These exchange flows through the Strait of Tiran are substantially larger than the net flows through the Straits. About 3 × 104 m3s−1 enters the Gulf near the surface, and leaves at depth through the Strait. The exchange varies annually with a net annual mean of 1.8 × 104 m3s−1. Surface water temperature may approach 28 oC during summer months and fall to just above 20 oC in winter. The generally weak currents (10 cm s−1) in the northern Gulf of Aqaba are largely driven by the prevailing down-Gulf winds and by the semi-diurnal internal tides generated in the Strait of Tiran. The annual meteorological measurements demonstrate that the wind speed fluctuates within a range of 0–12 ms−1 (mean 4.5 ± 2.4 ms−1). Moreover, a harmonic change of wind speed appears during summer causing a diurnal cycle that is represented by strong winds during daytime and relatively weaker winds during the night. Meanwhile, northerly winds (NNW-NNE) dominate over the study area and represent about 85% of total measurements. Mean values of air temperature range between 32.2 ± 3.16 °C in summer and 17.6 ± 3.46 °C in winter. The minimum humidity recorded in summer is 13% compared to a maximum of 83% in winter. The maximum sea level range, with reference to Global Mean Sea Level (MSL), during the year 2013 was 154.3 cm. The highest value was 101.7 cm observed on December 12, and the lowest value was −52.6 cm recorded in April 23. The pH at coastal and offshore waters of the Jordanian Gulf of Aqaba fluctuates around 8.3 with very minor temporal and spatial variations. This is typical for all coral reef waters because these waters are always saturated with calcium carbonate, which acts as a buffer and resists change in the pH. Inorganic nutrients (ammonia, nitrate, nitrite, phosphate and silicate) are essential for marine phytoplankton productivity and growth. Higher concentrations of nutrients and chlorophyll a concentrations occur during winter that are attributed to deep water vertical mixing during winter. Cross-shore mixing (from shallow to offshore waters) due to density currents (gravity currents) has been recently documented. This process drives coastal water down slope offshore when it gets cooler at night. The increased nutrient concentrations in the euphotic zone enhance primary productivity, resulting in higher phytoplankton abundance and increased chlorophyll a concentrations. Water column stratification and high irradiance during summer result in a depletion of the inorganic nutrients in the upper waters by enhanced primary productivity at the subsurface level (50–75 m). Ammonium concentration fluctuates irregularly around 0.4 μM with a tendency to higher concentrations during the winter months (January to March). Nitrate and nitrite concentrations during the last five years showed a regular shift from a summer low (0.10 and 0.01 µM) to relatively high early winter values (0.6 and 0.25 µM). Phosphate concentrations are generally low during summer (~0.02 µM) and high during winter (~0.10 µM). Silicate concentrations show the same trend with 1.0 µM during summer and ~2.0 µM in the winter. Dissolved oxygen concentrations at the Gulf of Aqaba show a regular pattern, inversely proportional to that of temperature, with a range of 6.4 to 7.4 mgl−1, indicating that the effects of the other ecosystem variables are masked by temperature. Waters of the Gulf of Aqaba are very well balanced in terms of respiration and photosynthesis and well ventilated due to the annual deep mixing with a saturation of 100%.

The midocean ridge system is a continuous tectonic feature over 60,000 km in length which covers an area equal to that of all the continents (Figure 1). It is the longest single geological structure on the surface of the Earth.Associated with the center of the ridge over much of its length is a fracture or rift which is the locus for many shallow earthquakes. Although the ridge system is generally restricted to the ocean basins, it crosses the continental margins at several points. One point is off the west coast of Mexico, where it extends through the Gulf of Baja California and into the fracture zones of the western United States; another point, located in the Indian Ocean, extends through the Gulf of Aden into the Red Sea. Here it bifurcates, one branch extending north to the Gulfs of Suez and Aqaba, the Dead Sea, and the Jordan valley, the other branch extending south to the great east African rift‐valleys. Topographic profiles across the system (Figure 2) illustrate the changes occurring as one goes from continent to ocean. The Gulf of Aqaba is a narrow rift marked by negative Bouguer gravity anomalies which, like the Gulf of Suez, bears a close resemblance to the east African rifts. The rift zone is much wider in the Red Sea, and it is marked by positive Bouguer gravity anomalies and, in the southern part especially, by very strong magnetic anomalies in the central portion. Seismic refraction measurements indicate that the shelves of the Red Sea are founded upon downdropped continental crustal blocks (5.8 km/sec), whereas the axial trough is based on high‐velocity (7+ km/sec) basic material (Figure 3). Similar high velocities are found in the Gulf of Aden, where the soundings indicate a rift to the west grading into a low ridge with a median rift as one moves toward the Indian Ocean. In the Indian Ocean a true ocean ridge system is found with an axial rift marked by numerous earthquake epicenters and frequently by a distinctive magnetic anomaly. Although there are few seismic refraction measurements in the Indian Ocean, the structure must be similar to other parts of the ridge system where velocities of 7+ km/sec are found at relatively shallow depths. Heat flow measurements from the Atlantic, Pacific, and Indian oceans show systematically higher values in the vicinity of the ridge, although the amount of increase varies (Figures 4 and 5). Heat flow measurements in the marginal Gulf of Aden and in the Gulf of Lower California also reveal higher than normal values. Several wells drilled in the Imperial valley just north of the Gulf of Lower California have encountered bottom hole temperatures in excess of 550°C and an unusually high concentration of minerals in the brine. Of a few measurements made recently in Lake Nyasa, the most reliable indicated high values due to a fairly local heat source.

The Red Sea divides at its northern end into two arms, the Gulf of Suez and the Gulf of Aqaba, separated by the triangular promontory of Sinai. The distinctive configuration is instantly recognisable and familiar to every modern student with any serious interest in the near east. The northern bifurcation of the Red Sea has been known to geographers for centuries, though as late as the eighteenth century many maps were published from distinguished cartographical houses showing the Red Sea with a single point at its northern end. In this study, the development of the cartographic presentation of the northern end of the Red Sea is examined.