Beach wrack is an important supplier of nutrients and organic matter to sandy beach ecosystems and underlying subterranean estuaries (STEs), producing metabolic hotspots in these otherwise organic carbon- and nutrient-poor environments. To assess the impact of beach wrack type (e.g., marine, terrestrial, plant, animal) and environmental settings (e.g., tidal inundation, precipitation, and solar irradiation) on nutrient and dissolved organic matter (DOM) release, a series of leaching experiments was conducted. Quantities of leached nutrients and dissolved organic carbon (DOC) were determined, and DOM molecular composition was investigated using Fourier-transform ion cyclotron resonance mass spectrometry (FT-ICR-MS). Millimolar—to molar amounts of DOC and dissolved nitrogen were released from the beach cast per kg dry weight, with type of wrack and leaching medium (fresh- vs. saltwater) exerting the biggest influences. Exemplary for animal cast, jellyfish leached up to two 100-fold more, mostly organic, nitrogen compared to all other beach wrack types. FT-ICR-MS data of solid-phase extracted DOM indicated that beach wrack releases compounds with putative mono- and oligosaccharide-, amino acid- and vitamin-type molecular formulae, which likely serve as valuable substrate for heterotrophic microorganisms. DOM from the brown seaweed Fucus sp. was more aromatic than seawater DOM and even beach wrack of terrestrial origin, probably from structural components and secondary metabolites such as phlorotannins. We conclude that DOM and nutrient release from beach wrack strongly depends on wrack type and leaching medium, may obscure molecular provenance proxies (e.g., terrestrial indices), and adds a nutritional boost to infiltrating sea- and rainwater which likely impact microbial respiration rates in the STE.

海滩残骸是沙滩生态系统和地下河口 (STE) 营养物和有机物的重要供应者，在这些有机碳和营养物贫乏的环境中产生代谢热点。为了评估海滩残骸类型（例如海洋、陆地、植物、动物）和环境设置（例如潮汐淹没、降水和太阳辐射）对营养物和溶解有机物 (DOM) 释放的影响，进行了一系列浸出实验进行了。测定浸出营养物和溶解有机碳 (DOC) 的量，并使用傅里叶变换离子回旋共振质谱 (FT-ICR-MS) 研究 DOM 分子组成。每千克干重的海滩铸件释放出毫摩尔至摩尔量的 DOC 和溶解氮，其中残骸类型和浸出介质（淡水与咸水）的影响最大。作为动物粪便的典范，水母的氮浸出量比所有其他海滩残骸类型多 100 倍，其中大部分是有机氮。固相提取的 DOM 的 FT-ICR-MS 数据表明，海滩残骸释放出具有假定的单糖、寡糖、氨基酸和维生素型分子式的化合物，这些化合物可能作为异养微生物的有价值的底物。来自棕色海藻 Fucus sp. 的 DOM。比海水 DOM 甚至陆地来源的海滩残骸更具芳香性，可能来自结构成分和次生代谢产物，如叶草单宁。我们得出的结论是，海滩残骸中的 DOM 和养分释放很大程度上取决于残骸类型和浸出介质，可能会掩盖分子来源代理（例如，、陆地指数），并增加渗透海水和雨水的营养，这可能会影响 STE 中的微生物呼吸速率。