Maroof A. Khalaf

Ecological and geochemical characteristics of bottom habitats at the northern Jordanian coast of the Gulf of Aqaba

A detailed study to assess the environmental conditions of the benthic habitats at the northern tip of the Gulf of Aqaba has been carried out during the summer of 2003. The texture, geochemical, and biogenic characteristics of bottom sediments as well as a description and distribution of corals, seagrass, fish species, and fish assemblages have been investigated. Results showed that the sea bottom at the study site is mainly a non-coralline sandy bottom covered with seagrass. Well-developed seagrass beds covered about 70–98% of the bottom. No coral cover was recorded. This is to be expected because of the absence of hard substrate and because of high loads of suspended matter. The seagrass habitat in the area serves as important nursery grounds for the fish larvae and hosts sea urchins and sea cucumbers. The bottom sand in the area was undisturbed, animal tracks were rare, but bioturbated holes and mounds were abundant. Bottom surface sediments were fine-grained, black with high quartz, feldspar, and mica, and low in mud content. Chemically, these sediments had low calcium carbonate, organic nitrogen, and high total phosphorus concentrations, suggesting that the sediment mineral composition is derived from existing metamorphic rocks, by weathering and erosion. The biogenous part of the sediments was mainly calcium carbonate, consisting of shells or coverings of some micro- and macro-organisms. The number and diversity of fish species inhabiting the survey site are typical of seagrass-bed sandy-bottom habitats. Some of the fish species observed are characteristic of this site and very rarely found elsewhere on the Jordanian coast. About half the fish population in the area belong to six families: Labridae (12%), Pomacentridae (7%), Mullidae (7.%), Apoginidae (6%), Chaetodontidae (6%), and Gobiidae (6%).

The status of coral reefs on the Jordanian coast of the Gulf of Aqaba, Red Sea

Abstract The Jordanian coast of the Gulf of Aqaba was intensively surveyed during the year 2004 to assess the health of the coral reefs in Jordan. Permanent line transects were laid on the reef flat, at depths of 8 m and 15 m at eight sites, and selected benthos components were studied. It was found that the distribution of hard corals increases gradually from north to south and that the 15 m deep transects had the highest coverage of hard corals. On the other hand, soft corals showed the highest coverage at sites where industrial activities are taking place. Coral death was low along the Jordanian coast and is comparable to surveys made in previous years, though protection measures are needed at the sites where industrial and recreational activities are focused. The hotels area, the phosphate loading berth and the Tala Bay sites had more than 40% seagrass coverage and were classified as seagrass habitats. Giant clams were hardly found on Jordan’s reefs and it is suggested that they should be considered as endangered species. It is concluded that the coral reefs in Jordan are in good condition, although pressure resulting from the rapid development of the tourism, industry and construction sectors along the coast is expected to increase and to represent the major threat to this ecosystem in the future. Continuous monitoring is therefore suggested.

Developing artificial reefs for the mitigation of man-made coral reef damages in the Gulf of Aqaba, Red Sea: coral recruitment after 3.5 years of deployment

Abstract Human stresses on coral reefs have increased to levels threatening their existence on a global scale. In the Gulf of Aqaba, many coastal coral reefs have been damaged by human activities, while many others are threatened. To mitigate such negative impacts, we have constructed a state-of-the-art artificial reef and deployed it in the Gulf of Aqaba in December 2008. After 3.5 years, the data obtained have shown extensive coral recruitment rates on the deployed artificial reef. This was suggested to be due to the high structural complexity of the new AR design. The newly created habitat is expected to protect the natural reefs by reducing pressure on them. This strategy is expected not only to be of environmental value to the marine ecosystem, but also to enhance eco-tourism in the local community. Based on the results obtained, it is highly recommended to use artificial reefs for restoration purposes.

Spatial distribution of fifty ornamental fish species on coral reefs in the Red Sea and Gulf of Aden

Abstract The spatial distribution of 50 ornamental fish species from shallow water habitats on coral reefs were investigated using visual census techniques, between latitudes 11−29°N in the Red Sea, in Jordan, Egypt, Saudi Arabia, and Yemen, and in the adjacent Gulf of Aden in Djibouti. One hundred eighteen transects (each 100×5 m) were examined in 29 sites (3−8 sites per country). A total of 522,523 fish individuals were counted during this survey, with mean abundance of 4428.2 ± 87.26 individual per 500 m² transect. In terms of relative abundance (RA), the most abundant species were Blue green damselfish, Chromis viridis (RA=54.4%),followed bySea goldie, Pseudanthias squamipinnis (RA= 34.7), Whitetail dascyllus, Dascyllus aruanus (RA= 2.6%), Marginate dascyllus, Dascyllus marginatus (RA= 2.0),Red Sea eightline flasher Paracheilinus octotaenia (RA=1.0),andKlunzinger’s wrasse, Thalassoma rueppellii (0.7%). The highest number of species (S) per 500 m² transect was found on reefs at the latitude 20° in Saudi Arabia (S=21.8), and the lowest number of species was found at the latitude 15° in Djibouti (S=11.11). The highest mean abundance (8565.8) was found on reefs at latitude 20° in Saudi Arabia and the lowest mean abundance (230) was found on reefs at latitude 22°, also in Saudi Arabia. Whereas, the highest Shannon-Wiener Diversity Index was found in reefs at the latitude 22° (H`=2.4) and the lowest was found in reefs at the latitude 20° (H`=0.6). This study revealed marked differences in the structure of ornamental fish assemblages with latitudinal distribution. The data support the presence of two major biogeographic groups of fishes in the Red Sea and Gulf of Aden: the southern Red Sea and Gulf of Aden group and the group in the northern and central Red Sea. Strong correlations were found between live coral cover and the number of fish species, abundance and Shannon-Wiener Diversity indices, and the strength of these correlations varied among the reefs. A conclusion was done that environmental differences among the reefs and the habitats investigated were important components of abundance variations and species diversity of ornamental fish along latitudinal gradients in the Red Sea and the Gulf of Aden.

Assessment of seagrass communities along the Jordanian coast of the Gulf of Aqaba, Red Sea

Abstract The distribution and abundance of seagrass communities have been investigated from from three sites along the Jordanian coast of the Gulf of Aqaba. The results showed that the seagrass Halophila stipulacea has the widest distribution in all sites. However, the species Halodule uninervis and Halophila ovalis were less abundant and were found at the Tala Bay site and only at shallow depths. The seagrass distributions increased with increasing depth up to 12 m, and thereafter declined. However, in some shallow areas, seagrass is completely absent due to extensive human activities. On average, the highest seagrass cover from this study was recorded at the Tala Bay site (36.6%), followed by 29.9% and 22.9% at Phosphate Loading Berth and Hotel Area sites, respectively. The mean biomass of leaves for the seagrass species H. stipulacea averaged 104.2 g m−2. The values increase with depth, reaching maximum at 12 m depth and followed by decrease down. Changes in mean leaf density, length, width, number of shoots and shoot length in all sites closely followed changed in biomass. These could be attributed to decreasing irradiance and as an adaptive change response to lower light intensities and lower growth rates at deeper depths.

Community structure of the family Pomacentridae along the Jordanian coast, Gulf of Aqaba, Red Sea

Abstract The spatial distribution and community structure of the family Pomacentridae were studied at different depths and sites along the coast of the Gulf of Aqaba in seagrass and coral reef habitats. Sixteen coastal sites along the Jordanian coast were studied by the visual census technique. A total of 151,134 pomacentrid fishes representing 23 species were observed during 188 visual censuses at 96 belt transects, and 4 additional species were observed outside the transect lines. Six species accounted for 85% of all individuals. Results from cluster analysis of the studied sites based on percentage of benthic cover revealed two main groups: the seagrass and the coral reef dominated sites. Fishes were most abundant at 12 m depths in the coral dominated sites, while fewer numbers were found at reef flat and seagrass sites. This was attributed to the shelter, structural complexity and food availability in the coral reef sites. Pomacentrus trichourus and Amphiprion bicinctus were the most common pomacentrid fishes. Teixeirichthys jordani was restricted to the northern coast of the Gulf of Aqaba. Multivariate analysis of the pomacentrid community revealed certain associations of fishes with different habitats. Within the large group of coral reef associated fishes we could distinguish the following three groups: a group of species that occur at 12 m deep transects such as Chromis weberi and C. pembae; a group of species that occur only in the reef flat such as Plectroglyphidodon leucozonus and P. lacrymatus; a group of the most dominant and most common species such as Neopomacentrus miryae and Pomacentrus trichourus.

Two new records of fishes from the Red Sea

Abstract Two species of bony fishes, which had not previously been reported from the Red Sea, are recorded from Aqaba, Jordan, on the northern tip of the Gulf of Aqaba. Foa brachygramma (family Apogonidae) occurs throughout the Indo-Pacific from East Africa to the Hawaiian Islands. Caranx heberi (family Carangidae) was previously known from many coastal areas of the Indo-West Pacific. For each of the two new records a set of diagnostic characters is given, based on the specimens from Aqaba.

Five additional records of fishes in the Gulf of Aqaba, including Mola mola (Forskål, 1775), new for the Red Sea

Abstract Five species are reported for the first time in the Gulf of Aqaba: Chanos chanos (family Chanidae), Novaculichthys macrolepidotus (family Labridae), Grammatorcynus bilineatus (Family Scombridae), and Arothron immaculatus (family Tetraodontidae) were already known to occur in the Red Sea, but the pelagic, oceanodromous species Mola mola (family Molidae) is reported for the first time from the Red Sea. For each of the records a set of diagnostic characters is given, based on specimens from Aqaba.

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

&NA; 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 &mgr;g/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. Graphical abstract Figure. No caption available. HighlightsStonefish worlds most venomous fish ever encountered by man.Venom highly toxic; rat LD50 38 &mgr;g/kg.Serum enzymes significantly increased.Sever histological damages may occur in human victims.Potential risk and precautious measures should be taken.