Increasing turbidity in coastal waters reduces benthic irradiance levels and consequently poses a fundamental threat to benthic primary producers and the food webs they support. It is therefore necessary to better understand how important primary producers, such as kelp, can adapt both physiologically and morphologically to these declining light conditions. This study examines how variation in turbidity influences the morphology of the kelp Ecklonia radiata, and how this relates to photosynthetic performance, by measuring multiple morphological characteristics, photosynthesis‐irradiance response, and photosynthetic pigments in adult kelp across a large‐scale turbidity gradient. Kelp morphology was strongly related to variation in benthic irradiance among sites, but this was not consistent with morphological acclimation. Kelp at the most turbid sites had short stipes (< 0.4 m) and lower surface area to volume ratios (SA:V) than kelp at moderate to high‐light sites, which had long stipes (~ 1 m) and high SA:V. Photosynthetic parameters and pigment content also varied considerably in relation to benthic irradiance, with increased photosynthetic efficiency and pigment content at low‐light sites. However, maximum rates of photosynthesis were highest at high‐light sites and strongly positively related to higher SA:V of kelp at these sites. These results demonstrate that while physiological adaptation may increase photosynthetic efficiency at low‐light sites, maximum photosynthetic output is strongly related to thallus morphology rather than cellular acclimation. This suggests that the large‐scale variation in kelp morphology observed across the turbidity gradient likely has important consequences for overall primary production as well as other important ecosystem functions.

中文翻译：

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浊度梯度下海带Ecklonia radiata的形态和光合响应

沿海水域混浊度的增加降低了底栖辐照度，因此对底栖初级生产者及其所支撑的食物网构成了根本性威胁。因此，有必要更好地了解海藻等初级生产者如何在生理和形态上适应这些不断下降的光照条件。这项研究研究了浊度的变化如何影响海带Ecklonia radiata的形态，以及通过测量大浊度梯度中成年海带的多种形态特征，光合作用-辐照度响应和光合色素，将其与光合性能联系起来。海带形态与各部位底栖辐照度的变化密切相关，但这与形态适应不符。海藻在最浑浊的部位具有短柄（<0.4 m），表面积/体积比（SA：V）低于中度到高光部位的海藻，后者具有长柄（〜1 m）和高SA：V 。与底栖辐照度有关的光合参数和色素含量也有很大变化，在弱光处光合效率和色素含量增加。然而，最大的光合作用速率在高光部位最高，并且与这些部位海带的SA：V较高呈正相关。这些结果表明，虽然生理适应可能会增加弱光处的光合作用效率，但最大的光合作用输出与th体形态而不是细胞适应性密切相关。这表明在整个浊度梯度上观察到的海带形态的大规模变化可能对总体初级生产以及其他重要的生态系统功能具有重要影响。