Numerical models are a suitable tool to quantify impacts of predicted climate change on complex ecosystems but are rarely used to study effects on benthic macroalgal communities. Fucus vesiculosus L. is a habitat‐forming macroalga in the Baltic Sea and alarming shifts from the perennial Fucus community to annual filamentous algae are reported. We developed a box model able to simulate the seasonal growth of the Baltic Fucus–grazer–epiphyte system. This required the implementation of two state variables for Fucus biomass in units of carbon (C) and nitrogen (N). Model equations describe relevant physiological and ecological processes, such as storage of C and N assimilates by Fucus, shading effects of epiphytes or grazing by herbivores on both Fucus and epiphytes, but with species‐specific rates and preferences. Parametrizations of the model equations and required initial conditions were based on measured parameters and process rates in the near‐natural Kiel Outdoor Benthocosm (KOB) experiments during the Biological Impacts of Ocean Acidification project. To validate the model, we compared simulation results with observations in the KOB experiment that lasted from April 2013 until March 2014 under ambient and climate‐change scenarios, that is, increased atmospheric temperature and partial pressure of carbon dioxide. The model reproduced the magnitude and seasonal cycles of Fucus growth and other processes in the KOBs over 1 yr under different scenarios. Now having established the Fucus model, it will be possible to better highlight the actual threat of climate change to the Fucus community in the shallow nearshore waters of the Baltic Sea.

中文翻译：

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墨角藻底栖群落季节性生长的模型模拟

数值模型是量化预测的气候变化对复杂生态系统影响的合适工具，但很少用于研究对底栖大型藻类群落的影响。Fucus vesiculosus L.是波罗的海形成栖息地的大型藻类，据报道从多年生的Fucus群落向年度丝状藻类的转移令人震惊。我们制定了一个盒子模型能够模拟波罗的海季节生长墨角藻-grazer-真菌系统。这就需要以碳（C）和氮（N）为单位对付球藻生物量执行两个状态变量。模型方程式描述了相关的生理和生态过程，例如富克氏菌对C和N同化物的存储，附生植物的遮光作用或草食性放牧对岩藻和附生植物的影响，但具有特定物种的比率和偏好。模型方程式的参数化和所需的初始条件是基于海洋酸化的生物影响项目中近自然的Kiel户外Benthocosm（KOB）实验中测得的参数和处理速率。为了验证模型，我们将模拟结果与在环境和气候变化情景（即大气温度升高和二氧化碳分压）下于2013年4月至2014年3月持续进行的KOB实验中的观察结果进行了比较。该模型再现了墨角莲的大小和季节周期在不同情况下，一年以上KOB的增长和其他过程。现在已经建立了Fucus模型，将有可能更好地突出气候变化对波罗的海浅海近岸Fucus群落的实际威胁。