DataSheet_1_In situ carbon uptake of marine macrophytes is highly variable among species, taxa, and morphology.pdf

Macroalgae form important coastal ecosystems and are considered to be highly productive, yet individual macrophyte carbon uptake rates are poorly documented and methodologies for in situ assessments of productivity are not well developed. In this study, we employ a 13C enrichment method in benthic chambers to calculate carbon uptake rates and assess δ13C signatures of a large stock of nearshore benthic macroalgae varying in taxa and morphology in Southern California. Our objectives are to 1) identify the variability of carbon uptake and inorganic carbon use among individuals of the same species or morphology, and 2) establish accurate and accessible carbon uptake procedures for coastal benthic primary producers. We found no significant relationship between the observed ranges of environmental factors such as nutrient concentrations, PAR, temperature, conductivity, and productivity rates, suggesting that unique physiological complexions underpin the high variability of carbon uptake and δ13C in studied macrophyte samples. We consider three reasons our experimental carbon uptake rates are 3–4 orders of magnitude lower than existing literature, which reports carbon uptake in the same units despite using different methods: 1) underrepresentation of Pmax, 2) incomplete carbon fractionation corrections, and 3) reduced hydrodynamics within the benthic chambers.

大型藻类构成了重要的海岸生态系统，并被认为具有极高的生产力，然而，关于个体大型水生植物的碳吸收速率的记录却十分匮乏，且用于现场生产力评估的方法尚未得到充分发展。在本研究中，我们采用13C丰度增强法于海底室中计算碳吸收速率，并评估南加州近岸海底大型藻类样品的δ13C特征。我们的目标包括：1）识别同种或同形态个体之间碳吸收和无机碳利用的变异性；2）建立准确且易于操作的碳吸收程序，适用于海岸海底初级生产者。我们发现，环境因素如营养浓度、光合有效辐射（PAR）、温度、电导率和生产力速率的观测范围之间不存在显著关系，这表明独特的生理构成是研究样品中碳吸收和δ13C高变异性的基础。我们认为，我们的实验碳吸收速率比现有文献报道的低3至4个数量级的原因有三：1）Pmax（最大光合速率）的代表性不足；2）碳分数校正不完整；3）海底室内的水动力学条件减弱。