The dynamics and stoichiometry of dissolved organic carbon release by kelp: Carbon fixation, DOC release and nutrient uptake data

Canopy-forming kelps are foundational species in coastal ecosystems, fixing tremendous amounts of carbon, yet we know little about the ecological and physiological determinants of dissolved organic carbon (DOC) release by kelps. We examined DOC release by the bull kelp, Nereocystis luetkeana, in relation to carbon fixation, nutrient uptake, tissue nitrogen content, and light availability. DOC release was approximately 3.5 times greater during the day than at night. During the day, N. luetkeana blades released an average of 16.2% of fixed carbon as DOC. Carbon fixation increased with light availability but DOC release did not, leading to a lower proportion of fixed carbon released as DOC at high light levels. We found no relationship between carbon fixation and DOC release rates measured concurrently. Rather, DOC release by N. luetkeana blades declined with marginal significance as blade tissue nitrogen content increased and with experimental nitrate addition, supporting the role of stoi...

形成冠层的巨藻（kelp）是海岸生态系统中的关键建群物种，可固定巨量碳源，但目前学界对巨藻释放溶解有机碳（dissolved organic carbon, DOC）的生态与生理决定因素仍知之甚少。本研究以牛海带（Nereocystis luetkeana）为研究对象，探究了其DOC释放速率与碳固定、养分吸收、组织氮含量及光照可用性之间的关联。实验结果显示，牛海带的DOC日间释放量约为夜间的3.5倍。日间，牛海带的叶状体平均将16.2%的固定碳以DOC形式释放。碳固定速率随光照可用性提升而升高，但DOC释放速率并未同步增加，这使得高光环境下固定碳以DOC形式释放的占比更低。研究未发现同步测定的碳固定速率与DOC释放速率之间存在显著关联。与之相反，牛海带叶状体的DOC释放速率随叶状体组织氮含量升高以及实验添加硝酸盐呈边际显著下降趋势，这支持了stoi...的调控作用。