Over the past ten years, divers have noted a decrease in healthy coral cover and an increase in benthic algae in Vatia Bay, on the island of Tutuila, American Samoa. The cause for this is unknown, but one hypothesis is that nutrient pollution from the local village may be driving the coral decline. Excess nutrients (especially nitrogen and phosphorus) can impact corals directly by lowering fertilization success, and reducing both photosynthesis and calcification rates, or indirectly such as through stimulation of the growth of benthic algae. Declining coral health adversely affects the biodiversity of the Bay and likely decreases ecosystem services. The objectives of this study were to determine the nutrient status of Vatia Bay (i.e. are levels elevated) and attempt to use caffeine and sucralose as tracers to assess the potential importance of human waste to the nutrient budget of the system.

Water samples were collected monthly at sixteen sites, selected using a stratified random design, for analysis of nitrate, nitrite, ammonium, urea, total nitrogen, orthophosphorus, total phosphorus, silica and salinity. These data confirm that nutrient concentrations are elevated in the Bay, when compared to territorial water quality standards (total nitrogen < 0.15 mg N/L; total phosphorus < 0.02 mg P/L). Land based contributions of phosphorus and reactive nitrogen can enter the environment from a variety of sources, but in Vatia the most likely sources are piggeries and septic systems. Analysis of water samples for tracers of human waste (caffeine and sucralose) confirmed that human derived nutrients are contributing to the nutrient budget of the Bay. Caffeine was detected in 82% of samples and sucralose was detected in 51% of samples, definitively confirming that human waste is reaching the Bay. Additionally, sucralose concentrations are significantly correlated with some nutrient constituents, including urea, a major component of waste. These data are useful not only to enhance the understanding of the role that anthropogenic nutrients play in the biodiversity and ecosystem health of the Bay, but also serve as an important “baseline” against which to measure future change.

在过去的十年中，潜水员注意到美属萨摩亚图图伊拉岛上的瓦蒂亚湾的健康珊瑚覆盖减少，底栖藻类增加。原因尚不清楚，但有一个假设是当地村庄的养分污染可能正在推动珊瑚的衰退。过多的养分（尤其是氮和磷）可通过降低施肥成功率，降低光合作用和钙化速率而直接影响珊瑚，或间接地（例如通过刺激底栖藻类的生长）间接影响珊瑚。珊瑚健康下降对海湾的生物多样性产生不利影响，并可能减少生态系统服务。这项研究的目的是确定Vatia湾的营养状况（即

每月在16个地点收集水样，并采用分层随机设计选择，以分析硝酸盐，亚硝酸盐，铵，尿素，总氮，正磷，总磷，二氧化硅和盐度。这些数据证实，与领水质量标准相比（总氮<0.15 mg N / L；总磷<0.02 mg P / L），海湾中的养分浓度升高。磷和活性氮的陆基贡献可以通过多种来源进入环境，但是在瓦蒂亚，最有可能的来源是养猪场和化粪池系统。对人类粪便（咖啡因和三氯蔗糖）示踪物进行的水样分析证实，人类来源的养分为海湾的养分预算做出了贡献。在82％的样品中检出了咖啡因，在51％的样品中检出了三氯蔗糖，最终确认人类废物正在到达海湾。此外，三氯蔗糖的浓度与某些营养成分（包括尿素）密切相关，尿素是废物的主要成分。这些数据不仅有助于加深对人为养分在海湾生物多样性和生态系统健康中的作用的了解，而且还可以作为衡量未来变化的重要“基准”。