Abstract Macroalgae can incorporate the isotopic signature (δ15N) of their external environment and be used as ‘bioindicators’ to map and identify between multiple sources of anthropogenic nitrogen. However, evidence suggests that the isotopic signature of their tissues can also be influenced by a range of other factors, which could confound their use as a monitoring tool. Hence, this study aimed to better understand the factors affecting macroalgae isotopic signatures, using Chondrus crispus as a model species. This was achieved by exposing C. crispus to 15N-enriched NO3− and/or NH4+ at varying concentrations, temperatures and incubation times under controlled laboratory conditions. Longer incubation times promoted macroalgae δ15N values closer to that of the external nitrogen source. However, even after 28 days incubation, macroalgae δ15N was still >30‰ lower than the source. This suggests that the δ15N of C. crispus is unlikely to reach isotopic equilibrium with its external environment within a time frame that is feasible for most field studies. However, C. crispus can be used to highlight relative isotopic differences between sources even at very low nitrogen concentrations (

中文翻译：

---

孵化时间、温度和氮浓度对巨藻软骨藻同位素特征 (δ15N) 的影响

摘要 大型藻类可以结合其外部环境的同位素特征 (δ15N)，并用作“生物指标”来绘制和识别多种人为氮源。然而，有证据表明，它们组织的同位素特征也可能受到一系列其他因素的影响，这可能会影响它们作为监测工具的使用。因此，本研究旨在更好地了解影响大型藻类同位素特征的因素，使用卷曲软骨作为模型物种。这是通过在受控实验室条件下将 C.crispus 暴露于不同浓度、温度和孵育时间的富含 15N 的 NO3- 和/或 NH4+ 来实现的。更长的孵化时间促进了大型藻类 δ15N 值更接近外部氮源的值。然而，即使经过 28 天的孵化，大型藻类δ15N仍比源低>30‰。这表明，C.crispus 的 δ15N 不太可能在大多数实地研究可行的时间范围内与其外部环境达到同位素平衡。然而，即使在非常低的氮浓度下，C.crispus 也可用于突出来源之间的相对同位素差异。