Leigh Marine Laboratory, Institute of Marine Science, University of Auckland, Auckland, New Zealand.
Photosynth Res. 2019 Apr;140(1):21-38. doi: 10.1007/s11120-019-00636-7. Epub 2019 Mar 14.
Understanding the photoacclimation response of macroalgae across broad spatial and temporal scales is necessary for predicting their vulnerability to environmental changes and quantifying their contribution to coastal primary production. This study investigated how the photosynthesis-irradiance response and photosynthetic pigment content of the kelp Ecklonia radiata varies both spatially and seasonally among seven sites located across a turbidity gradient in the Hauraki Gulf, north-eastern New Zealand. Photosynthesis-irradiance curves were derived under laboratory conditions for whole adult E. radiata using photorespirometry chambers. Lab-derived photosynthesis-irradiance curves in summer were also compared with in situ measurements made on kelp at each of the seven study sites. Photosynthetic parameters and pigments showed clear seasonal patterns across all sites as demonstrated by higher photosynthetic pigment levels and photosynthetic efficiency occurring in autumn and winter, and higher maximum rates of photosynthesis and respiration occurring in summer. Lamina biomass was similar across sites, yet thalli exhibited a clear photokinetic response to increasing turbidity. At turbid sites photosynthetic pigment levels and photosynthetic efficiency was higher, and respiration and saturation and compensation irradiances lower, compared to high-light sites. The results presented here further our understanding of low-light acclimation strategies in kelp and highlight the degree of seasonality in photosynthetic parameters. Though E. radiata demonstrates a clear capacity to photoacclimate to a degrading light environment, further research is needed to investigate the extent to which the observed acclimation can offset the likely negative effects of increasing turbidity on kelp forest primary production.
了解大型藻类在广泛的空间和时间尺度上的光适应反应对于预测其对环境变化的脆弱性以及量化其对沿海初级生产力的贡献是必要的。本研究调查了新西兰东北部豪拉基湾浊度梯度上的七个地点的海带 Ecklonia radiata 的光合作用-光照响应和光合色素含量如何在空间和季节上发生变化。使用光呼吸室在实验室条件下为整个成年 E. radiata 得出光合作用-光照曲线。夏季还将实验室得出的光合作用-光照曲线与七个研究地点中每个地点的海带的现场测量进行了比较。光合作用参数和色素在所有地点都表现出明显的季节性模式，这表明秋季和冬季的光合色素水平和光合作用效率较高，夏季的最大光合作用和呼吸速率较高。叶片生物量在各地点相似，但藻体对浊度增加表现出明显的光动力学反应。与高光地点相比，在浑浊地点，光合色素水平和光合作用效率较高，呼吸作用、饱和和补偿辐照度较低。这里呈现的结果进一步加深了我们对海带低光适应策略的理解，并强调了光合作用参数的季节性程度。尽管 E. radiata 表现出对退化光照环境进行光适应的明显能力，但需要进一步研究来调查观察到的适应程度可以在多大程度上抵消浊度增加对海带林初级生产力的可能负面影响。
