Fuad A. Al-Horani

Bacterial population and biodegradation potential in chronically crude oil-contaminated marine sediments are strongly linked to temperature

Two of the largest crude oil-polluted areas in the world are the semi-enclosed Mediterranean and Red Seas, but the effect of chronic pollution remains incompletely understood on a large scale. We compared the influence of environmental and geographical constraints and anthropogenic forces (hydrocarbon input) on bacterial communities in eight geographically separated oil-polluted sites along the coastlines of the Mediterranean and Red Seas. The differences in community compositions and their biodegradation potential were primarily associated (P < 0.05) with both temperature and chemical diversity. Furthermore, we observed a link between temperature and chemical and biological diversity that was stronger in chronically polluted sites than in pristine ones where accidental oil spills occurred. We propose that low temperature increases bacterial richness while decreasing catabolic diversity and that chronic pollution promotes catabolic diversification. Our results further suggest that the bacterial populations in chronically polluted sites may respond more promptly in degrading petroleum after accidental oil spills.

Coral mucus fuels the sponge loop in warm- and cold-water coral reef ecosystems

Shallow warm-water and deep-sea cold-water corals engineer the coral reef framework and fertilize reef communities by releasing coral mucus, a source of reef dissolved organic matter (DOM). By transforming DOM into particulate detritus, sponges play a key role in transferring the energy and nutrients in DOM to higher trophic levels on Caribbean reefs via the so-called sponge loop. Coral mucus may be a major DOM source for the sponge loop, but mucus uptake by sponges has not been demonstrated. Here we used laboratory stable isotope tracer experiments to show the transfer of coral mucus into the bulk tissue and phospholipid fatty acids of the warm-water sponge Mycale fistulifera and cold-water sponge Hymedesmia coriacea, demonstrating a direct trophic link between corals and reef sponges. Furthermore, 21–40% of the mucus carbon and 32–39% of the nitrogen assimilated by the sponges was subsequently released as detritus, confirming a sponge loop on Red Sea warm-water and north Atlantic cold-water coral reefs. The presence of a sponge loop in two vastly different reef environments suggests it is a ubiquitous feature of reef ecosystems contributing to the high biogeochemical cycling that may enable coral reefs to thrive in nutrient-limited (warm-water) and energy-limited (cold-water) environments.

Anemonefish oxygenate their anemone hosts at night

SUMMARY Many stony coral-dwelling fishes exhibit adaptations to deal with hypoxia among the branches of their hosts; however, no information exists on the respiratory ecophysiology of obligate fish associates of non-coral organisms such as sea anemones and sponges. This study investigated metabolic and behavioral interactions between two-band anemonefish (Amphiprion bicinctus) and bulb-tentacle sea anemones (Entacmaea quadricolor) at night. We measured the net dark oxygen uptake (, μmol O2 h−1) of fish–anemone pairs when partners were separate from each other, together as a unit, and together as a unit but separated by a mesh screen that prevented physical contact. We also measured the effects of water current on sea anemone and quantified the nocturnal behaviors of fish in the absence and presence of host anemones in order to discern the impacts of anemone presence on fish behavior. Net of united pairs was significantly higher than that of both separated pairs and united pairs that were separated by a mesh screen. Anemone increased with flow rate from 0.5 to 2.0 cm s−1, after which remained constant up to a water flow rate of 8.0 cm s−1. Furthermore, the percentage time and bout frequency of flow-modulating behaviors by fish increased significantly when anemones were present. We conclude that physical contact between anemonefish and sea anemones elevates the of at least one of the partners at night, and anemonefish behavior at night appears to oxygenate sea anemone hosts and to augment the metabolism of both partners.

Differential recycling of coral and algal dissolved organic matter via the sponge loop

Corals and macroalgae release large quantities of dissolved organic matter (DOM), one of the largest sources of organic matter produced on coral reefs. By rapidly taking up DOM and transforming it into particulate detritus, coral reef sponges are proposed to play a key role in transferring the energy and nutrients in DOM to higher trophic levels via the recently discovered sponge loop. DOM released by corals and algae differs in quality and composition, but the influence of these different DOM sources on recycling by the sponge loop has not been investigated. Here, we used stable isotope pulse-chase experiments to compare the processing of naturally sourced coral- and algal-derived DOM by three Red Sea coral reef sponge species: Chondrilla sacciformis, Hemimycale arabica and Mycale fistulifera. Incubation experiments were conducted to trace 13C- and 15N-enriched coral- and algal-derived DOM into the sponge tissue and detritus. Incorporation of 13C into specific phospholipid-derived fatty acids (PLFAs) was used to differentiate DOM assimilation within the sponge holobiont (i.e. the sponge host vs. its associated bacteria). All sponges assimilated both coral- and algal-derived DOM, but incorporation rates were significantly higher for algal-derived DOM. The two DOM sources were also processed differently by the sponge holobiont. Algal-derived DOM was incorporated into bacteria-specific PLFAs at a higher rate while coral-derived DOM was more readily incorporated into sponge-specific PLFAs. A substantial fraction of the dissolved organic carbon (C) and nitrogen (N) assimilated by the sponges was subsequently converted into and released as particulate detritus (15–24% C and 27–49% N). However, algal-derived DOM was released as detritus at a higher rate. The higher uptake and transformation rates of algal- compared with coral-derived DOM suggest that reef community phase shifts from coral to algal dominance may stimulate DOM cycling through the sponge loop with potential consequences for coral reef biogeochemical cycles and food webs.

Allochthonous bioaugmentation in ex situ treatment of crude oil-polluted sediments in the presence of an effective degrading indigenous microbiome

Oil-polluted sediment bioremediation depends on both physicochemical and biological parameters, but the effect of the latter cannot be evaluated without the optimization of the former. We aimed in optimizing the physicochemical parameters related to biodegradation by applying an ex-situ landfarming set-up combined with biostimulation to oil-polluted sediment, in order to determine the added effect of bioaugmentation by four allochthonous oil-degrading bacterial consortia in relation to the degradation efficiency of the indigenous community. We monitored hydrocarbon degradation, sediment ecotoxicity and hydrolytic activity, bacterial population sizes and bacterial community dynamics, characterizing the dominant taxa through time and at each treatment. We observed no significant differences in total degradation, but increased ecotoxicity between the different treatments receiving both biostimulation and bioaugmentation and the biostimulated-only control. Moreover, the added allochthonous bacteria quickly perished and were rarely detected, their addition inducing minimal shifts in community structure although it altered the distribution of the residual hydrocarbons in two treatments. Therefore, we concluded that biodegradation was mostly performed by the autochthonous populations while bioaugmentation, in contrast to biostimulation, did not enhance the remediation process. Our results indicate that when environmental conditions are optimized, the indigenous microbiome at a polluted site will likely outperform any allochthonous consortium.

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.

Coral calcification: Use of radioactive isotopes and metabolic inhibitors to study the interactions with photosynthesis and respiration

In order to characterize the process of calcification in scleractinian corals, a series of laboratory experiments were conducted using radioactive isotopes. Labelled calcium, bicarbonate and glucose were used and the fates of the labelled tracers were followed in the skeleton and the tissue fractions of the coral Galaxea fascicularis. In addition, a variety of metabolic inhibitors were used to test the effects of various enzymes and processes on the incorporation rates. The incorporation rate of 45Ca into the coral skeleton decreased to about one-fifth upon inhibition of metabolic respiration by the specific inhibitor NaCN suggesting a major role of metabolic respiration in coral calcification, and decreased to one-half upon inhibition of carbonic anhydrase by the specific inhibitor acetazolamide indicating a role of the enzyme in the process. The results obtained have also shown that corals are able to incorporate carbon from seawater bicarbonate and added glucose in both skeleton and tissue fractions. The process of incorporation was influenced by light conditions, carbonic anhydrase, respiration and photosynthesis. The incorporation rate of 14C-HCO was reduced to about one-tenth in the skeleton, and one-fifth in the tissue, upon inhibition of carbonic anhydrase suggesting a major influence of the enzyme in the incorporation process. The inhibition of photosynthesis had more influence on the tissue incorporation rate of the tracer than the skeleton suggesting that photosynthesis is the main process responsible for tissue use of seawater bicarbonate in the coral. 14C-glucose incorporation into the skeleton was mainly affected by NaCN addition and to a lesser extent by dichlorophenyldimethylurea (DCMU) addition, while the tissue fraction was mainly affected by NaCN addition. It was concluded that respiration and photosynthesis, in addition to the enzyme carbonic anhydrase, are limiting factors for the process of calcification in the coral, and that various forms and sources of carbon can be used in coral calcification and tissue growth.

Heavy metals signature of human activities recorded in coral skeletons along the Jordanian coast of the Gulf of Aqaba, Red Sea

The concentrations of six heavy metals were studied in five living coral species and their fossil counterparts collected along the Jordanian Coast of the Gulf of Aqaba. The study aimed at investigating the validity of using coral skeletons as bioindicators for environmental pollution by heavy metals in the Gulf of Aqaba, Red Sea. The skeletal samples of the collected corals were acid digested and analyzed for Cd, Cu, Fe, Mn, Pb, and Zn content using flame atomic absorption spectrophotometer. The results obtained have shown that higher concentrations of heavy metals were found in coral skeletons from areas hosting intense developments and human activities. The massive Porites sp. coral tended to accumulate the highest metal concentrations among the other species (except for Mn). This was due to interspecific differences or selectivity of heavy metals between different coral species. It was noteworthy that fossil coral species recorded higher average metal concentrations than their living counterparts; this was attributed to surface contamination due to prolonged burial of the fossil corals in sediment over the years. The study concluded that corals (specially the massive Porites species) are vulnerable to the accumulation of high concentrations of heavy metals in their skeletons and therefore can serve as proxies to monitor environmental pollution.

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.

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.