We explore potential management strategies for short-term mitigation efforts of cyanobacterial blooms informed by process-based dynamic models. We focus on the case where blooms are linked to the existence of alternative stable states, such that, under the same conditions but depending on the past, a lake may be dominated either by cyanobacteria (“blue algae”), causing a harmful algal bloom, or by green algae and macrophytes in a clear water state. Changing conditions may cause the favourable clear water state to disappear through a tipping point, causing the lake to switch rapidly to the turbid cyanobacteria state. At the same time, it may take considerable effort to undo this tipping and return to the favourable state. We identify four different strategies for bloom mitigation in this scenario: Doing nothing, reacting to a bloom, resetting the lake at a later point, and preventing the bloom. We found that these strategies have different cost profiles. The optimal strategy depends on many factors, including the relative costs of blooms and interventions, the time during which the environment favours a bloom and the bifurcation structure that determines where in parameter space blooms appear and disappear. In general, low bloom costs and short bloom times favour not intervening, while high bloom costs favour prevention. In between, waiting for more favourable conditions before resetting to a clear state may be preferable, especially for long bloom times, where constant intervention becomes expensive. Transient dynamics are also relevant, with a trade-off between minimising intervention effort and maximising bloom reversal speed.

中文翻译：

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基于模型的蓝藻水华短期控制的替代稳定状态的后果

我们通过基于过程的动态模型探索蓝藻水华短期缓解工作的潜在管理策略。我们重点关注水华与替代稳定状态的存在相关的情况，例如，在相同条件下但取决于过去，湖泊可能以蓝藻（“蓝藻”）为主，从而导致有害的藻华，或由清水状态下的绿藻和大型植物组成。条件的变化可能会导致有利的清水状态通过临界点消失，导致湖泊迅速转变为浑浊的蓝藻状态。同时，可能需要相当大的努力才能消除这种倾斜并返回到有利的状态。在这种情况下，我们确定了缓解水华的四种不同策略：不采取任何措施、对水华做出反应、稍后重置湖泊以及防止水华。我们发现这些策略具有不同的成本概况。最佳策略取决于许多因素，包括水华和干预的相对成本、环境有利于水华的时间以及决定水华在参数空间中出现和消失的分叉结构。一般来说，低开花成本和短开花时间有利于不干预，而高开花成本有利于预防。在这两者之间，在重置到清晰状态之前等待更有利的条件可能是更好的选择，特别是对于长时间的开花，持续的干预变得昂贵。瞬态动态也是相关的，需要在最小化干预努力和最大化水华逆转速度之间进行权衡。