Institute for Marine and Antarctic Studies, University of Tasmania, Hobart, Tasmania, 7001, Australia.
Griffith School of Environment, Australian Rivers Institute - Coast and Estuaries, Nathan Campus, Griffith University, Brisbane, Queensland, 4111, Australia.
J Phycol. 2021 Oct;57(5):1375-1391. doi: 10.1111/jpy.13198. Epub 2021 Aug 23.
Dissolved organic carbon (DOC) release by seaweeds (marine macroalgae) is a critical component of the coastal ocean biogeochemical carbon cycle but is an aspect of seaweed carbon physiology that we know relatively little about. Seaweed-derived DOC is found throughout coastal ecosystems and supports multiple food web linkages. Here, we discuss the mechanisms of DOC release by seaweeds and group them into passive (leakage, requires no energy) and active release (exudation, requires energy) with particular focus on the photosynthetic "overflow" hypothesis. The release of DOC from seaweeds was first studied in the 1960s, but subsequent studies use a range of units hindering evaluation: we convert published values to a common unit (μmol C · g DW · h ) allowing comparisons between seaweed phyla, functional groups, biogeographic region, and an assessment of the environmental regulation of DOC production. The range of DOC release rates by seaweeds from each phylum under ambient environmental conditions was 0-266.44 μmol C · g DW · h (Chlorophyta), 0-89.92 μmol C · g DW · h (Ochrophyta), and 0-41.28 μmol C · g DW · h (Rhodophyta). DOC release rates increased under environmental factors such as desiccation, high irradiance, non-optimal temperatures, altered salinity, and elevated dissolved carbon dioxide (CO ) concentrations. Importantly, DOC release was highest by seaweeds that were desiccated (<90 times greater DOC release compared to ambient). We discuss the impact of future ocean scenarios (ocean acidification, seawater warming, altered irradiance) on DOC release rates by seaweeds, the role of seaweed-derived DOC in carbon sequestration models, and how they inform future research directions.
海藻（海洋大型藻类）释放的溶解有机碳（DOC）是沿海海洋生物地球化学碳循环的关键组成部分，但我们对其知之甚少。海草来源的 DOC 存在于整个沿海生态系统中，并支持多种食物网联系。在这里，我们讨论了海藻释放 DOC 的机制，并将其分为被动（泄漏，不需要能量）和主动释放（分泌，需要能量），特别关注光合作用的“溢出”假说。海藻释放 DOC 的研究始于 20 世纪 60 年代，但随后的研究使用了一系列阻碍评估的单位：我们将已发表的值转换为一个共同的单位（μmol C·g DW·h），以允许在海藻门、功能群、生物地理区域之间进行比较，并评估 DOC 产生的环境调控。在环境条件下，每个门的海藻释放的 DOC 速率范围为 0-266.44 μmol C·g DW·h（绿藻），0-89.92 μmol C·g DW·h（褐藻）和 0-41.28 μmol C·g DW·h（红藻）。在干旱、高光强、非最佳温度、盐度改变和溶解二氧化碳（CO2）浓度升高等环境因素下，DOC 释放速率增加。重要的是，干燥的海藻（与环境相比，DOC 释放增加了<90 倍）释放的 DOC 最多。我们讨论了未来海洋情景（海洋酸化、海水变暖、光照改变）对海藻释放 DOC 速率的影响，海草来源的 DOC 在碳封存模型中的作用，以及它们如何为未来的研究方向提供信息。
