Impacts of Urbanization-Driven Coastal Eutrophication on Coral Reefs

Abstract

Rapid urbanization has fundamentally altered coastal environments by intensifying nutrient loading from agriculture, wastewater, aquaculture, and land-use change. This review synthesizes current studies on the effects of urbanization-driven eutrophication on coral reefs, from individual physiological stress to population decline, community restructuring, and loss of ecosystem services. Excessive inputs of nitrogen and phosphorus, especially under imbalanced N:P ratios, disrupt coral–algae symbiosis, reduce calcification, and heighten susceptibility to bleaching. At the population and community levels, sustained nutrient enrichment causes sensitive coral species to decline. Elevated dissolved inorganic nitrogen significantly alters the composition and relative abundance of coral symbiotic microorganisms, reshaping microbial community structure and consequently impacting the overall health and ecological function of coral reefs. These changes have disrupted crucial ecosystem services, including fishery yields, coastal protection, and cultural services, all of which are essential for the well-being of coastal communities. The review also highlights that integrated land-sea management, improved wastewater treatment, restoration of ecological buffer zones, and coordinated cross-regional governance are urgently needed to address the pressures of eutrophication. These measures are vital for maintaining the ecological integrity and socioeconomic benefits of coral reefs in expanding urban coastal areas.