Stable isotope analysis of preserved natural‐history specimens from long‐term storage can provide useful data about energy flow and trophic structure in ecosystems of the past. Nitrogen isotope values from primary producers are used as critical food web baselines, while both nitrogen and carbon isotopes expose the presence of sewage contamination and nutrient runoff. Seaweed specimens being prepared for long‐term storage are often fixed in formalin prior to being dried or transferred into a storage liquid, but the effects of this fixative on nitrogen and carbon stable isotope values of marine primary producers have not been investigated. We evaluated the effects of formalin on macroalgal and cyanobacterial stable isotope values. For this purpose, we analyzed δ¹⁵N and δ¹³C values of 41 pairs of formalin‐preserved vs. dried seaweed specimens stored for up to 5 yr. While neither isotope was consistently altered by formalin when all seaweeds were pooled, δ¹⁵N values were overall less variable than δ¹³C values. However, formalin preservation lowered δ¹³C values in Ochrophyta by 0.2% on average. Neither isotope was affected by duration of formalin preservation. Because formalin‐exposed samples show similar δ¹⁵N and δ¹³C values to dried samples, formalin‐exposed specimens can be used to accurately assess nutrient dynamics and food webs of historic marine ecosystems provided that one has sufficient sample sizes of seaweeds.

中文翻译：

---

福尔马林保存对海藻碳氮稳定同位素的影响：时光倒流的基础

长期保存的自然历史标本的稳定同位素分析可以提供有关过去生态系统中能量流和营养结构的有用数据。初级生产者的氮同位素值被用作食物网的关键基准，而氮同位素和碳同位素都暴露了污水污染和养分径流的存在。准备长期保存的海藻标本通常在干燥或转移到存储液之前先用福尔马林固定，但尚未研究这种固定剂对海洋初级生产者氮和碳稳定同位素值的影响。我们评估了福尔马林对大藻类和蓝细菌稳定同位素值的影响。为此，我们分析δ ¹⁵ N和δ ¹³储存长达5年的41对福尔马林保存与干海藻标本的C值。虽然没有同位素一致地通过福尔马林改变当所有海藻被汇集，δ ¹⁵的N值比可变总体更少δ ¹³ C值。然而，福尔马林保存降低δ ^13个在淡色藻总门C值由0.2％的平均。两种同位素均不受福尔马林保存时间的影响。因为福尔马林暴露的样品显示出类似的δ ¹⁵ N和δ ¹³干燥样品，暴露于福尔马林的样品的C值可用于准确评估历史海洋生态系统的养分动态和食物网，只要其中有足够数量的海藻。