Description: Presently, the anthropogenic impacts on coral reefs are increasing globally. Two of the main human-based stressors are eutrophication and overfishing, which may change bottom-up (nutrient) and top-down (feeding) controls leading to altered benthic coral reef communities. These alterations include a shift from diverse, structurally complex coral assemblages to less diverse, structurally simple algae-dominated assemblages. Thresholds and magnitude of changes in the benthic community depend on the severity of human-based impacts as well as on the buffering capacity (resilience) which is unique to each ecosystem. Therefore, it is important to assess and validate potential impacts of human-based stressors in different ecosystems in geographic regions. In the Red Sea, especially near Jeddah, these impacts and possible resulting shifts to macroalgae dominated reefs have scarcely been investigated yet. Thus the aim of this study was to assess the possible effect of overfishing on already eutrophied reefs by assessing the benthic community on artificial settlement tiles with particular emphasis on coral recruitment and algae biomass. Exclusion experiments were conducted in oligotrophic non-impacted off-shore and on eutrophic impacted near-shore reefs over 3 months during spring 2012. Results showed hat additional nutrients promote algae growth, which further trap particulate matter and led to a reduction in crustose coralline algae and further feasible settling space for coral recruits which in addition led to a lowered coral recruitment success. A similar outcome was found when herbivores got excluded as this promotes theincrease of algal biomass also resulting in a higher deposition of particulate matter leading to a reduction of crustose coralline algae and in the end a lowered coral recruitment. Supplementary, in situ feeding experiments were conducted to investigate apossible change in feeding pressure on benthic communities in eutrophic versus oligotrophic reefs, expecting an increase in herbivory at the eutrophic reefs. In contrast however, both carnivory and herbivory was higher in the oligotrophic off-shore reefs,while feeding pressure was generally lower near-shore and a change towards enhanced herbivory in near-shore reefs could not be found. An oversupply of algae material in near-shore reefs could be a possible explanation. Another new aspect of potential eutrophication effects was investigated, by assessing the potential change of the chemical anti-feeding defence of the coral Pocillopora verrucosa. Interestingly, aquaria feeding experiments with feeding pellets containing chemical extract from near-shore and off-shore coral specimen revealed a higher repellent efficiency against predators in corals from near-shore eutrophied waters. To reveal the underlying mechanisms further studies are required. In conclusion it could be said that the eutrophication has a profound influence on the reef ecosystems as it promotes macroalgae growth which is particularly increased when herbivory is reduced. As other studies have shown before, reefs in Jeddah are facing a dramatic change. The fish population seems to be able to cope with the enhanced algae growth; however, a change in recruitment success is already visible. It further seems that some coral species are benefiting from the nutrient enhancement as their predator deterrence possibilities are enhanced. However it is still unknown what the underying factors are behind this process are and if further increasing nutrient values may favour or decrease this mechanism of predator defence.