English Chance J, Bell Tom W, Opalk Keri, Siegel David A, Carlson Craig A
Marine Science Institute/Department of Ecology, Evolution and Marine Biology, University of California Santa Barbara, Santa Barbara, CA, USA.
Department of Applied Ocean Physics and Engineering, Woods Hole Oceanographic Institution, Woods Hole, MA, USA.
Commun Biol. 2025 Aug 7;8(1):1172. doi: 10.1038/s42003-025-08477-y.
Kelp forests form some of the most productive areas on earth and are proposed to sequester carbon in the ocean, largely in the form of released dissolved organic carbon (DOC). Here we investigate the role of environmental, seasonal and age-related physiological gradients on the partitioning of net primary production (NPP) into DOC by the canopy forming giant kelp (Macrocystis pyrifera). Rates of DOC production were strongly influenced by an age-related decline in physiological condition (i.e. senescence). During the mature stage of giant kelp development, DOC production was a small and constant fraction of NPP regardless of tissue nitrogen content or light intensity. When giant kelp entered its senescent phase, DOC production increased substantially and was uncoupled from NPP and light intensity. Compositional analysis of giant kelp-derived DOC showed that elevated DOC production during senescence was due to the solubilization of biomass carbon, rather than by direct exudation. We coupled our incubation and physiological experiments to a novel satellite-derived 20-year time series of giant kelp canopy biomass and physiology. Annual DOC production by giant kelp varied due to differences in standing biomass between years, but on average, 74% of the annual DOC production by giant kelp was due to senescence. This study suggests DOC may be a more important fate of macroalgal NPP than previously recognized.
海带森林构成了地球上一些生产力最高的区域，并且被认为在海洋中固存碳，主要是以释放的溶解有机碳（DOC）的形式。在这里，我们研究了环境、季节和与年龄相关的生理梯度对形成冠层的巨型海带（巨藻）将净初级生产力（NPP）分配为DOC的作用。DOC的产生速率受到与年龄相关的生理状况下降（即衰老）的强烈影响。在巨型海带发育的成熟阶段，无论组织氮含量或光照强度如何，DOC的产生都是NPP的一个小且恒定的部分。当巨型海带进入衰老阶段时，DOC的产生大幅增加，并且与NPP和光照强度解耦。对源自巨型海带的DOC的成分分析表明，衰老期间DOC产量的增加是由于生物量碳的溶解，而不是直接渗出。我们将我们的培养和生理实验与一个新的由卫星得出的20年巨型海带冠层生物量和生理时间序列相结合。巨型海带每年的DOC产量因年份之间现存生物量的差异而有所不同，但平均而言，巨型海带每年DOC产量的74%是由于衰老。这项研究表明，DOC可能是大型藻类NPP比以前认识到的更重要的归宿。
