Impact of Water Quality Deterioration on Coral Reef Community Structure in the Northern Red Sea, Egypt

Abstract

F ifteen water quality parameters and nine coral community variables were assessed in eight reef sites along the Red Sea coast of Egypt. Coral reef environments are suffering of stress from increased anthropogenic activities, particularly in the vicinity of heavily populated and touristic areas such as Hurghada, Ain Al-Sukhna and Sharm El-Sheikh. Increased terrestrial runoff of sediments, nutrients, organic matter and other pollutants are the main causes of water quality deterioration in the investigated reef sites. The results showed that bioerosion of corals by sea urchins, and enhanced abundance of macroalgae and consequent competitive overgrowth of corals were the major reasons of coral damage observed in the area of study. Population density of sea urchins exhibited significant and positive correlations with the majority of eutrophication parameters. Salinity was significantly and negatively correlated with live hard coral cover. Exceeding levels of DIN and TSM above the threshold concentrations for eutrophication were reported to be indirectly and adversely affecting coral reefs through stimulating the growth of macroalgae, enhancing sea urchin density and reducing water transparency. The results support the predictions of bottom-up hypothesis that confirm the critical role of eutrophication in structure of coral reef community.

Heavy metals distribution in the coral reef ecosystems of the Northern Red Sea

“…As the majority of metals in the present study, Fe concentration and bioconcentration factor were not signiWcantly diVerent among the interested coral species (ANOVA, F = 0.36, df = 30, P > 0.05 and F = 0.16, df = 30, P > 0.05, respectively), but they showed marked variation between these species ( ) collected from site III are a direct result to the highest concentration of dissolved Fe registered at this site (Table 1) and probably to the higher salinity level (Ramos et al 2004;Ali and Hamed 2006). In contrast to the majority of metals reported in the current study, the highest average of Fe concentration (115.53 § 85.45 gg…”

“…The highest Ni concentration contained in soft corals Sinularia spp. collected from site III (186 § 8.54 gg ¡1 , Table 2) were probably due to the increased Ni uptake rate associated with elevated dissolved Ni concentrations (5.8 § 0.99 gl ¡1 ) and high salinity level (annual mean = 41.78 ppt) reported in this area (Dallinger and Rainbow 1993;Ramos et al 2004;Ali and Hamed 2006). Also Sinularia spp.…”