One billion tons of carbon are annually transported to the global ocean, and the fate of this carbon hinges not only on marine processing rates, but also on freshwater processing during downstream transport. Using a cotton-strip assay, we assessed the decomposition of organic matter in marine and freshwater sites and simulated its downstream transport from freshwater to the sea by translocating cotton strips approximately half-way through the freshwater incubation period. We observed faster decomposition in the sea relative to the stream and interestingly, an inhibitory effect of stream incubation on subsequent decomposition in the sea. Total nitrogen content and ∂¹⁵N in the cotton strips were both greater in the strips incubated entirely in the sea, suggesting greater microbial activity in the marine habitat. Our results lend needed insights into global carbon cycling, the factors that govern organic-carbon processing, and highlight the importance of connections that exist among some of Earth's major ecosystems.

中文翻译：

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流到海的实验揭示了淡水驻留对海洋中有机物分解的抑制作用

每年有 10 亿吨碳被输送到全球海洋，这些碳的命运不仅取决于海洋加工速度，还取决于下游运输过程中的淡水加工。使用棉条测定法，我们评估了海洋和淡水场所中有机物的分解，并通过在淡水潜伏期大约一半的时间将棉条转移到海洋中来模拟其从淡水到海洋的下游运输。我们观察到海洋中的分解相对于河流更快，有趣的是，河流孵化对随后在海洋中的分解有抑制作用。总氮含量和∂ ¹⁵棉条中的 N 在完全在海中孵化的棉条中都更高，这表明海洋生境中的微生物活动更大。我们的研究结果为全球碳循环提供了必要的见解，这些因素控制了有机碳加工，并强调了地球上一些主要生态系统之间存在联系的重要性。