Nutrient enrichment has degraded many of the world’s estuaries by amplifying algal production, leading to hypoxia/anoxia, loss of vascular plants and fish/shellfish habitat, and expansion of harmful blooms (HABs). Policies to protect coastal waters from the effects of nutrient enrichment require information to determine if a water body is impaired by nutrients and if regulatory actions are required. We compiled information to inform these decisions for San Francisco Bay (SFB), an urban estuary where the best path toward nutrient management is not yet clear. Our results show that SFB has high nutrient loadings, primarily from municipal wastewater; there is potential for high algal production, but that production is not fully realized; and SFB is not impaired by hypoxia or recurrent HABs. However, our assessment includes reasons for concern: nitrogen and phosphorus concentrations higher than those in other estuaries impaired by nutrient pollution, chronic presences of multiple algal toxins, a recent increase of primary production, and projected future hydroclimatic conditions that could increase the magnitude and frequency of algal blooms. Policymakers thus face the challenge of determining the appropriate protective policy for SFB. We identify three crucial next steps for meeting this challenge: (1) new research to determine if algal toxins can be reduced through nutrient management, (2) establish management goals as numeric targets, and (3) determine the magnitude of nutrient load reduction required to meet those targets. Our case study illustrates how scientific information can be acquired and communicated to inform policymakers about the status of nutrient pollution, its risks, and strategies for minimizing those risks.

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旧金山湾的营养状况及其管理意义

营养物质的丰富化通过扩大藻类的产生而使世界许多河口退化，导致缺氧/缺氧，维管植物和鱼类/贝类生境的丧失以及有害水华（HAB）的扩大。保护沿海水域免受养分富集影响的政策要求提供信息，以确定水体是否受到养分损害，以及是否需要采取监管措施。我们汇总了有关信息，以为旧金山湾（SFB）的这些决策提供依据。旧金山湾是一个城市河口，目前尚不清楚通往营养管理的最佳途径。我们的结果表明，SFB的养分含量很高，主要来自市政废水。藻类产量很高，但生产尚未完全实现；SFB不会因缺氧或复发性HAB而受损。但是，我们的评估包括引起关注的原因：氮和磷的浓度高于其他河口，受营养物质污染，多种藻毒素的长期存在，初级产量的近期增加以及未来水文气候条件的影响，这些条件可能会增加藻华的数量和频率。因此，决策者面临着为SFB确定适当的保护政策的挑战。我们确定了应对这一挑战的三个关键的下一步：（1）确定是否可以通过营养管理减少藻毒素的新研究；（2）建立管理目标作为数字目标；（3）确定所需减少营养负荷的幅度达到这些目标。我们的案例研究说明了如何获取和交流科学信息，以使决策者了解养分污染的状况，其风险，