The effect of seawater environmental factors on the corals of Wailingding Island in the Pearl River Estuary

Highlights

• The seawater environment and corals around Wailingding Island were investigated.

• Increased DIN concentration was an important factor in coral reduction.

• DIN disturbed corals by inducing coral-algal competition and phosphate starvation.

• Coral protection should control Wailingding island’s sewage discharge in dry season.

Abstract

Corals are important marine resources, Wailingding Island is one of the few islands with coral growth in the South China Sea, but the deterioration of seawater environment seriously threatens coral survival. In this study, the coral distribution, temperature, transparency, salinity, pH, dissolved oxygen (DO), chemical oxygen demand (COD), NH4+-N, NO3–N and PO43–P around Wailingding Island were investigated to determine the influential environmental factors affecting coral growth. The results showed that temperature, transparency, salinity, pH, DO and COD were within the ranges required by coral; however, the dissolved inorganic nitrogen (DIN) concentration increased by 200% to approximately 0.33 mg/L from 1990 to 2019, and it was speculated to be an important factor in coral reduction, as DIN can disturb corals by inducing coral-algal competition and phosphate starvation. Pearl River runoff (PRR) and human activity on Wailingding Island were the dominant nutrient sources in the wet season and dry season, respectively, and local coral protection measures should focus on controlling sewage discharge in consideration of this seasonal difference. In addition, the optimum ranges of above environmental factors for local coral were proposed to provide a reference for discharge control. These results will contribute to the coral protection of Wailingding Island.

Lu Y., Ding Z., Li W., Chen X., Yu Y., Zhao X., Lian X. & Wang Y., in press. The effect of seawater environmental factors on the corals of Wailingding Island in the Pearl River Estuary. Continental Shelf Research. Article (subscription required).

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