It is widely hypothesized that noncalcifying macroalgae will be more productive and abundant in increasingly warm and acidified oceans. Macroalgae vary greatly in the magnitudes and interactions of responses of photosynthesis and growth to multiple stressors associated with climate change. A knowledge gap that exists between the qualitative “macroalgae will benefit” hypothesis and the variable outcomes observed is regulation of physiological mechanisms that cause variation in the magnitudes of change in primary productivity, growth, and their covariation. In this context, we developed a model to quantitatively describe physiological responses to coincident variation in temperature, carbonate chemistry and light supply in a representative bicarbonate‐using marine macroalga. The model is based on Ulva spp., the best understood dissolved inorganic carbon uptake mechanism among macroalgae, with data enabling synthesis across all parameters. At boundary layer pH < 8.7 most inorganic carbon is taken up through the external carbonic anhydrase (CA_ext) mechanism under all conditions of photosynthetic photon flux density, temperature, and boundary layer thickness. Each 0.1 unit decline in pH causes a 20% increase in the fraction of diffusive uptake of CO₂ thereby lessening reliance on active transport of bicarbonate. Modeled downregulation of anion exchange‐mediated active bicarbonate transport associated with a 0.4 unit decline in pH under ocean acidification is consistent with enhanced growth up to 4% per day without increasing photosynthetic rate. The model provides a means to quantify magnitudes of change in productivity under factorial combinations of changing temperature, pCO₂, and light supply anticipated as climate changes.

中文翻译：

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气候变化中大型藻类碳捕获调控的多应力模型

广泛的假设是，在日益温暖和酸化的海洋中，非钙化大型藻类将更富生产力。大型藻类在光合作用和生长对多种与气候变化有关的压力源的响应的大小和相互作用方面差异很大。定性的“微藻类将受益”假说与观察到的可变结果之间存在知识鸿沟，这是生理机制的调节，这些生理机制引起初级生产力，生长及其协变量变化幅度的变化。在这种情况下，我们开发了一个模型，用于定量描述使用碳酸氢盐的典型海洋大型藻类对温度，碳酸盐化学物质和光供应同时发生变化的生理反应。该模型基于Ulvaspp。，这是大型藻类中最了解的溶解性无机碳吸收机制，其数据可实现所有参数的合成。在pH <8.7的边界层上，在光合作用光子通量密度，温度和边界层厚度的所有条件下，大多数无机碳通过外部碳酸酐酶（CA _ext）机理吸收。pH值每降低0.1个单位，CO ₂的扩散吸收比例就会增加20％从而减少了对碳酸氢根主动转运的依赖。在海洋酸化作用下，阴离子交换介导的活性碳酸氢盐转运的模型下调与pH值下降0.4个单位相关，这与每天最多增加4％的生长而不增加光合速率的现象相一致。该模型提供了一种方法，可以在温度，p CO ₂和气候变化带来的预期供热的因子组合下量化生产率的变化幅度。