Spatial distribution of sewage pollution on a Hawaiian coral reef Marine Pollution Bulletin

While sewage pollution is contributing to the global decline of coral reefs, its offshore extent and direct reef impacts from water column mixing and benthic seeps are poorly documented. We addressed this knowledge gap on a Hawaiian coral reef using sewage indicator and benthic cover measurements, macroalgal bioassays, and a pollution scoring tool. Fecal indicator bacteria (FIB) and nutrient concentrations were spatially variable in surface and benthic waters, with shoreline values being highest. Shoreline macroalgae δ15N and %N indicated high nitrogen loads containing sewage, while offshore surface and benthic values suggested lower nitrogen loads from environmental sources. Coral cover was negatively correlated with FIB, macroalgal δ15N, and nutrient concentrations. Benthic salinity and temperature measurements detected daily tidal groundwater pulses which may explain these associations. While pollution scores revealed that sewage was largely concentrated along the shoreline, results showed some reached the reef and may be contributing to its declining condition. Grant no. NA14NOS4820087

尽管污水污染正加剧全球珊瑚礁的衰退，但目前对其离岸影响范围，以及因水团混合与底质渗流直接造成的珊瑚礁损害，相关记录仍十分匮乏。本研究针对夏威夷一处珊瑚礁开展调查以填补该认知空白，实验手段涵盖污水指示物与底栖覆盖度测定、大型藻类生物测定及污染评分工具。粪便指示菌（Fecal indicator bacteria, FIB）与营养盐浓度在表层及底栖水体中呈现空间异质性，沿岸区域数值最高。沿岸大型藻类的δ¹⁵N值与总氮占比（%N）表明其承载了含污水来源的高氮负荷，而离岸区域的表层与底栖藻类则显示出源自环境本底的较低氮负荷。珊瑚覆盖度与FIB、大型藻类δ¹⁵N值及营养盐浓度呈显著负相关关系。底栖盐度与温度监测结果发现了每日出现的潮汐性地下水脉冲，这或可解释上述关联机制。尽管污染评分结果显示污水主要集中于沿岸区域，但研究发现部分污水已扩散至珊瑚礁区域，或正加剧其衰退态势。资助编号：NA14NOS4820087