An integrated pre-development environmental baseline for the NEOM coastal region (Saudi Arabian Red Sea)

Background Coastal mega-developments require robust environmental baselines to distinguish natural biogeochemical variability from emerging anthropogenic pressures. Establishing pre-development reference conditions is essential for detecting future impacts on marine ecosystems, yet comprehensive baseline datasets remain scarce in rapidly developing coastal regions. This need is particularly urgent in the Red Sea, where coastal are exposed to increasing climate-driven pressures. Using an integrated line-of-evidence approach, this study establishes a pre-development baseline for the NEOM coastal region in the northern Saudi Red Sea. Dissolved trace metals (Fe, Zn, Cu, Ni, Pb, Cd, Co), inorganic nutrients (NO2⁻, NO3⁻, PO43⁻, NH4⁺, SiO4), chlorophyll-a, organic UV filters, and pharmaceutical and personal care products (PPCPs) were quantified. Environmental DNA samples were used to assess DNA traces of species associated with anthropogenic presence (bovine, ovine, and salmon). Sampling was conducted in spring and autumn 2024. Results Biogeochemical conditions in NEOM were compared with those of Thuwal (low urbanization) and Jeddah (high urbanization). Jeddah showed higher concentrations of chlorophyll-a, silicate, nitrite, nitrate, and copper, while Thuwal showed higher chlorophyll-a and copper but lower nitrate, phosphate and ammonium, both relative to NEOM. Seasonal variability was also observed, most notably as a marked increase in zinc dispersion in Thuwal during autumn. Most organic UV filters and PPCPs were below their respective quantification limits, although erythromycin was consistently detected, whereas naproxen and caffeine occurred sporadically. eDNA screening for the three target species (bovine, ovine, and salmon) was consistently negative. Conclusions By documenting the biogeochemical conditions in a coastal region showing relatively low concentrations of key biogeochemical indicators while undergoing rapid planned coastal transformation, this study establishes a critical pre-development baseline against which future environmental change associated with NEOM infrastructure, tourism, and maritime activity expansion in the Red Sea can be assessed.