Giant clam growth in the Gulf of Aqaba is accelerated compared to fossil populations.

The health of reef-building corals has declined due to climate change and pollution. However, less is known about whether giant clams, reef-dwelling bivalves with a photosymbiotic partnership similar to that found in reef-building corals, are also threatened by environmental degradation. To compare giant clam health against a prehistoric baseline, we collected fossil and modern Tridacna shells from the Gulf of Aqaba, Northern Red Sea. After calibrating daily/twice-daily growth lines from the outer shell layer, we determined that modern individuals of all three species (Tridacna maxima, T. squamosa and T. squamosina) grew faster than Holocene and Pleistocene specimens. Modern specimens also show median shell organic δ15N values 4.2‰ lower than fossil specimens, which we propose is most likely due to increased deposition of isotopically light nitrate aerosols in the modern era. Nitrate fertilization accelerates growth in cultured Tridacna, so nitrate aerosol deposition may contribute to faster growth in modern wild populations. Furthermore, colder winter temperatures and past summer monsoons may have depressed fossil giant clam growth. Giant clams can serve as sentinels of reef environmental change, both to determine their individual health and the health of the reefs they inhabit.

Biochemical and histopathological effects of the stonefish (Synanceia verrucosa) venom in rats.

The Reef Stonefish (Synanceia verrucosa) is one of the most dangerous venomous fish known, and has caused occasional human fatalities. The present study was designed to examine some of the pathological effects of the venom from this fish in Sprague Dawley rats. Crude venom was extracted from venom glands of the dorsal spines of stonefish specimens collected from coral reefs in the Gulf of Aqaba (in the northeastern branch of the Red Sea). The rats were given intramuscular injections of the venom and acute toxicity and effect on selected serum marker enzymes as well as normal architecture of vital organs were evaluated. The rat 24 h LD50 was 38 µg/kg body weight. The serum biochemical markers; alanine transaminase (ALT), lactate dehydrogenase (LDH) and creatine kinase (CK) increased after 6 h of administration of a sub lethal dose of the venom and remained significantly raised at 24 h. Amylase levels also significantly increased after venom injection. The venom caused histological damage manifested as an interstitial hemorrhage, inflammatory cell infiltration, and necrosis. The demonstrated rises in the levels of different critical biochemical parameters in the serum may have led to the observed abnormal morphological changes in these organs. These results may account for some of the clinical manifestations observed in victims of stonefish envenomation. Thus, the presented data provide further in vivo evidence of the stonefish toxic effects that may threaten human life and call for the need for special measures to be considered.

Phytoplankton dynamics in the Gulf of Aqaba (Eilat, Red Sea): a simulation study of mariculture effects.

The northern Gulf of Aqaba is an oligotrophic water body hosting valuable coral reefs. In the Gulf, phytoplankton dynamics are driven by an annual cycle of stratification and mixing. Superimposed on that fairly regular pattern was the establishment of a shallow-water fish-farm initiative that increased gradually until its activity was terminated in June 2008. Nutrient, water temperature, irradiation, phytoplankton data gathered in the area during the years 2007-2009, covering the peak of the fish-farm activity and its cessation, were analyzed by means of statistical analyses and ecological models of phytoplankton dynamics. Two datasets, one from an open water station and one next to the fish farms, were used. Results show that nutrient concentrations and, consequently, phytoplankton abundance and seasonal succession were radically altered by the pollution originating from the fish-farm in the sampling station closer to it, and also that the fish-farm might even have influenced the open water station.

Assessment of gamma-emitting radionuclides in sediment cores from the Gulf of Aqaba, Red Sea.

The Gulf of Aqaba is the only seaport in Jordan which currently has intense activities such as industrial development, phosphate ore exportation, oil importation, shipping, commercial and sport fishing. Most of these activities, especially the phosphate ore exportation, could cause serious radiological effects to the marine environment. Thus, it is essential to investigate the level of the radioactivity concentrations to establish a baseline database, which is not available yet in the Gulf of Aqaba. Radioactivity concentrations of gamma-emitting radionuclides in core and beach sediments of the Gulf of Aqaba were investigated. Core sediments were collected from five representative locations for three different water column depths (5, 15 and 35 m). The results showed that the activity concentrations of 238U, 235U and 226Ra for both seafloor and beach sediments from the phosphate loading berth (PLB) location to be higher than those from other investigated locations and more than twice as high as the worldwide average; the 238U activity concentration was found to vary from 57 to 677 Bq kg(-1). The results also showed that there is little variation of radioactivity concentrations within the core length of 15 cm. The calculated mean values of the radium equivalent activity Ra(eq), the external hazard index, H(ex), the absorbed dose rate and the annual effective dose for the beach sediment in PLB location were 626 Bq kg(-1), 1.69, 263 nGy h(-1) and 614 µSv y(-1), respectively. These values are much higher than the recommended limits that impose potential health risks to the workers in this location. As for other studied locations, the corresponding values were far below the maximum recommended limit and lies within the worldwide range.

Marine litter in coral reef areas along the Jordan Gulf of Aqaba, Red Sea.

Composition and abundance of submerged marine litter at six selected sites within a coral reef area along the Jordanian coast of the Gulf of Aqaba have been estimated. The litter was collected in clean up voluntary campaigns that took place in the period between 25 August 2003 and 29 February 2004. A total of 10,506 items weighing 1159 kg were collected during the survey. Mean litter density in the individual sampling sites varied between 1 and 6 items/m(2) with an overall mean density of 2.8 items/m(2). The mean weight of the collected items per sampling site varied between 0.06 and 1.06 kg/m(2) with an overall mean of 0.31 kg/m(2). Plastic accounted for 42% of the collected items, fishing gear was the second most abundant (31%) while metal was the third most abundant item (17%). By comparison, cardboard constituted 1%, and rubber and other items accounted for less than 1% of the total items collected during the campaigns. Approximately 61% of the plastics consisted of bags followed by bottles (24%), plastic containers and sheets accounted for 13 and 2%, respectively. Statistical analysis indicates no significant differences between the sites in terms of litter count and weight. Potential sources are pointed out and recommendations and actions to address the problem are suggested.

Litter pollution on the Jordanian shores of the Gulf of Aqaba (Red Sea).

Litter was assessed on three beaches along the Jordanian coast of the Gulf of Aqaba, south of the town Aqaba, monthly during 1994 and 1995, in order to determine its nature, extent and possible sources. The overall mean was about 5 and 3 items/m(2) in 1994 and 1995, respectively. Approximately a total of 14,000 m(2) were examined and a total of 101,000 items were noted, 67,000 during 1994 and 34,000 in 1995. More than 50% of the litter was plastic and the remainder wood, glass, cardboard, Styrofoam, metal and other materials. Most litter appears to be from local land-based or near shore sources, although there are some regional influences as well. The main local sources are the passenger port, the cargo port and the beach goers. The findings are compared with other regions of the world. The amount of litter is related to distance of the beach from the main sources, and shape, physiography and orientation of the beach. Spatial and seasonal variations are examined and discussed, and actions and measures to combat the problem on local and regional levels are suggested.