Mohammad I. Badran

Endoscopic exploration of Red Sea coral reefs reveals dense populations of cavity-dwelling sponges

Framework cavities are the largest but least explored coral reef habitat. Previous dive studies of caverns, spaces below plate corals, rubble and artificial cavities suggest that cavity-dwelling (coelobite) filter-feeders are important in the trophodynamics of reefs. Quantitative community data are lacking, however, as the bulk of the narrow crevices interlacing the reef framework are inaccessible to conventional analysis methods. Here we have developed endoscopic techniques to explore Red Sea framework crevices up to 4 m into the carbonate rock, revealing a large internal surface (2.5–7.4 m2 per projected m2 reef) dominated by encrusting filter-feeders. Sponges alone provided up to 60% of coelobite cover, outweighing epi-reefal filter-feeder biomass by two orders of magnitude. Coelobite community filtration removed more than 60% of the phytoplankton in the course of its less than 5-minute passage through the crevices, corresponding to an uptake of roughly 0.9 g carbon m-2 d-1. Mineralization of the largely allochthonous organic material is a principal source of nutrients supporting coral and algal growth. The supply of new material by coelobites may provide a key to understanding the ‘coral reef paradox’—a rich ecosystem thriving in nutrient-poor water.

Seasonal dynamics of phytoplankton in the Gulf of Aqaba, Red Sea

Seawater samples were collected biweekly from the northern Gulf of Aqaba, Red Sea, for Phytoplankton analysis during the period May 1998 to October 1999. Microscopic counts and HPLC methods were employed. Procaryotic and eucaryotic ultraplankton dominated throughout most of the year, with larger nano- and microplankton making up only 5% of the photosynthetic biomass. Moderate seasonal variations in the 0–125 m integrated Chl a contrasted with a pronounced seasonal succession of the major taxonomic groups, reflecting the changes in the density stratification of the water column: Prochlorococcus dominated during the stratified summer period and were almost absent in winter. Chlorophyceae and Cryptophyceae were dominant during winter mixing but scarce or absent during summer. Diatoms and Synechococcus showed sharp and moderate biomass peaks in late winter and spring respectively, but remained at only low Chl a levels for the rest of the year. Chrysophyceae, Prymnesiophyceae and the scarce Dinophyceae showed no clear seasonal distribution pattern. The implications of alternating procaryotic and eucaryote dominated algal communities for the Red Sea pelagic food web are discussed.

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%).

Desalination: an imminent solution for the future water needs in the Aqaba Special Economic Zone (ASEZ)☆

Abstract Jordan has recently given distinguished attention to its single and extremely limited sea outlet — Aqaba. An innovative governing system is being established. Aqaba has been declared as a Special Economic Zone Authority. The main objectives of the new authority are to develop Aqaba as a haven for commerce, a destination for tourism, and an incubator for technology. A strong limiting factor to this ambitious planning is the scarcity of fresh water. The conventional water resources utilized to satisfy the increasing water demand will reach the maximum sustainable yield in less than 5 years. At present, water supply is abstracted from groundwater aquifers and amounts to about 16.4 million m3/y (MCM/y). According to the final master plan of the ASEZA, the total consumption is expected to increase by about 5 MCM/y in the first 5 years, 11 MCM/y in the following 5 years, and about 30 MCM/y by the end of 20 years. The ultimate allocation for ASEZA from the conventional water resources from the Disi non-renewable aquifer does not exceed 17.5 MCM/y. This identified gap in water supply has definitely to be filled by unconventional water resources such as desalination of seawater and brackish water. The location of ASEZ alongside the Red Sea and over partly brackish aquifers does qualify it for desalination. However, the ASEZA Environmental Commission is currently identifying significant issues to be considered in the mitigation measures when designing desalination plants in order to alleviate adverse environmental impacts to the ecosystem. This paper discusses the expected future water demands, the ASEZA acceptable water standards for the different water uses, and the environmental impact of the desalination plants and their respective mitigation measures.

Sea-water seasonal changes at a heavy tourism investment site on the Jordanian northern coast of the Gulf of Aqaba, Red Sea

The Gulf of Aqaba exhibits a strong seasonality due to convective mixing during winter and stratification during summer. The present study provides a detailed appraisal of summer and winter sea-water characteristics at the northern coast of the Gulf of Aqaba, that is witnessing rapid development and increasing changes in its geomorphological characteristics. Sea-water temperature, salinity, nutrients, and chlorophyll a concentrations were measured biweekly at five coastal and four cross-sectional stations during the periods February to April and July to September 2004. Meteorological conditions were continuously recorded at the Marine Science Station. The coastal study sites included four open coastal stations and a marina with one-way exchange with the open water. The effect of convective mixing was clearly apparent on the sea-water characteristics. Natural seasonal characteristics of higher nutrients and chlorophyll a concentrations were recorded during winter at most of the open coastal stations. In the cross-sectional stations, the concentrations of nutrients and chlorophyll a were not different between the surface and the bottom during winter, but the bottom waters had generally higher concentrations during summer. Some deviations from the natural seasonal cycle were recorded at the marina and other coastal stations. Here, higher nutrient and chlorophyll a concentrations were recorded in summer than in winter. These deviations that are most likely due to anthropogenic effects are discussed.

Phosphate enrichment in the northern Gulf of Aqaba: Regulation by carbonate sediments and impact on nitrogen elevation

The effect of carbonate sediment in regulating phosphate concentrations in sea water was investigated by laboratory incubation experiments using different sediment types. Incubation experiments were made with two types of sediments: uncontaminated sediment from a marine reserve and contaminated sediment with deposited phosphate powders. Fluxes of inorganic nitrogen and phosphate were estimated from linear regressions of solute concentrations over incubation periods. Ammonium and phosphate fluxes were about twofold higher in the uncontaminated sediment that had significantly lower organic carbon and total phosphate concentrations than in the phosphate-contaminated sediment. To test the effect of dissolved phosphate on increasing nitrogen fixation, additional incubation experiments were carried out using treated carbonate and silicate sediments with added dissolved phosphate (20 μM). Incubations were made under sterile conditions with HgCl2 added to distinguish between biologically enhanced processes and pure physicochemical processes. The adsorption rate of phosphate onto carbonate sediment was about twice that onto silicate sediments. No nitrogen elevation either as ammonium or as nitrate was observed in the soluble phosphate enrichment incubations. In conclusion, this study demonstrates the importance of the regulation of soluble phosphate concentrations in carbonate sediment environments where the carbonate sediment acts as a buffering system keeping soluble phosphate concentrations at certain steady-state levels. The study also demonstrates the lack of evidence on enhancement of nitrogen concentrations due to the increase phosphate concentrations.