Abstract
Corals and coral-reef ecosystems have been known to be extremely sensitive to environmental pollution, which effects on growth and calcification of their skeletons. Diffused phosphate dust during loading and shipment in seawater was found to cause serious impacts on corals by inhibiting calcification in their skeletons. Calcium concentrations in cultured fragments of coral Stylophora pistillata from Phosphate Terminal (PT) site in the Jordanian Gulf of Aqaba were investigated and compared with fragments from the same colony cultured in the Marine Science Station (MSS) site as marine protected area. Energy Disperse X-rays (EDX) spectroscopy and Scanning Electron Microscopy (SEM) were employed to determine the elemental composition of coral fragments and identify their microstructural characteristics, respectively. EDX results showed that coral samples from the Phosphate Terminal (PT) site were poorly mineralized with significantly low concentrations of calcium which were only about 12% of those from the MSS control site. Moreover, higher amounts of O and C in the elemental analysis of corals from the PT site indicated domination of organic matrix content in their skeleton which is typical for corals under phosphate pollution stress. This result was in accordance with the SEM images of the PT samples which exhibited alteration in their microstructure morphology resembling organic matrix as a major constituent, unlike the SEM images from the MSS protected area. These results strongly suggest that phosphate dust which is diffused during exportation through loading and shipping in the Gulf of Aqaba has adverse impacts on corals and marine ecosystem through decreasing calcium mineralization in their skeletons.
Highlights
Coral reef ecosystems were found to be highly sensitive to changes in the surrounding physicochemical environment [1]
This paper reports remarkable findings including low calcium observation and microstructure alteration in samples of coral skeleton taken from Phosphate Terminal (PT) compared to samples from the Marine Science Station (MSS) control site
The Energy Disperse X-rays (EDX) elemental quantitative analysis shows that coral samples from the Phosphate Terminal (PT) were poorly mineralized; having very low Ca concentration of only 2.56%, which is around 12% of the average in the MSS control sample (21.95%)
Summary
Coral reef ecosystems were found to be highly sensitive to changes in the surrounding physicochemical environment [1]. Coastal coral reefs are increasingly exposed to growing loads of nutrients, sediments and pollutants which made terrestrial and coastal runoff a growing concern for most of the 104 countries endowed with coral reefs [2] [3]. The Jordanian coastline is only 27 km long, and lies in one of the most important economic development districts in Jordan. Due to high rates of industrial developments, population growth, and tourism, the Gulf of Aqaba has been heavily impacted by human activities, especially along its northern part [6]. The export in the port of Aqaba is dominated by the phosphates [7], and the Port Corporation of Aqaba operates a large Phosphate export facility that is capable of loading 2200 tons of material per hour [8]
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