Rothe J, Gleixner G
Institut für Okologie, Friedrich-Schiller-University, Jena, Germany.
Isotopes Environ Health Stud. 2000;36(3):285-301. doi: 10.1080/10256010008036388.
We evaluated the use of delta15N- and delta13C-values to monitor the development of food web complexity and biodiversity in a regenerating ecosystem. Therefore a model food chain was established feeding cultivated woodlice (Porcellio dilatatus) on a cellulolytic fungus (Chaetomium globosum) grown on cellulose paper. Two diets of different quality (C:N ratios of 54 vs. 200) with different delta15N- (1.3% vs. 3.1%) but identical delta13C-values caused low and high dietary stress in animals of treatment A and B, respectively. After an incubation time of 7 weeks amount, elemental and isotopic composition of collected faeces and exuviae as well as woodlice and remaining food were determined. The increase of delta15N-values of woodlice relative to the diet was 5.7% and 2.5% in treatments A and B, respectively, whereas delta13C-shifts were 1.0% and 1.6%, showing a reverse relationship. Modelling of elemental and isotopic mass balances indicated that faeces recycling explains the unexpected high 15N-enrichments. Moreover, 13C-enrichments were positively correlated to the degree of starvation. Considering the effects of starvation and recycling of faeces, stable isotopes represent a useful tool to elucidate trophic interactions in regenerating food webs.
我们评估了利用δ¹⁵N值和δ¹³C值来监测一个再生生态系统中食物网复杂性和生物多样性的发展情况。因此，构建了一个模型食物链，用在纤维素纸上生长的一种纤维素分解真菌（球毛壳菌）来喂养养殖的鼠妇（Porcellio dilatatus）。两种质量不同（碳氮比分别为54和200）、δ¹⁵N值不同（分别为1.3%和3.1%）但δ¹³C值相同的食物，分别给处理A和B组的动物造成了低和高的饮食压力。经过7周的孵化期后，测定了所收集粪便、蜕皮以及鼠妇和剩余食物的元素和同位素组成。处理A和B组中，鼠妇相对于食物的δ¹⁵N值增加分别为5.7%和2.5%，而δ¹³C的变化分别为1.0%和1.6%，呈现出相反的关系。元素和同位素质量平衡的模型表明，粪便再循环解释了意外出现的高¹⁵N富集现象。此外，¹³C富集与饥饿程度呈正相关。考虑到饥饿和粪便再循环的影响，稳定同位素是阐明再生食物网中营养相互作用的有用工具。
