Addressing assumptions: variation in stable isotopes and fatty acids of marine macrophytes can confound conclusions of food web studies
Addressing assumptions: variation in stable isotopes and fatty acids of marine macrophytes can confound conclusions of food web studies
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DOI：
10.3354/meps10310
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发表时间：
2013-01-01
影响因子：
2.5
通讯作者：
Simenstad, Charles A.
中科院分区：
文献类型：
--
作者：
Dethier, Megan N.;Sosik, Elizabeth;Simenstad, Charles A.
使用生物标记物来阐明消费者饮食的研究通常必须假设这些标记在空间和时间上是相对不变的。我们在3个不同的日期对10种海洋大型植物(大型藻类和海草)的多种稳定同位素(MSI：Delta C-13、Delta N-15、Delta S-34)和脂肪酸进行了验证，并在东北太平洋沿海的3个地点对MSI进行了量化。对于所有的比较，我们发现生物标记物在物种、地点和日期之间存在显著差异；此外，总是存在显著的地点x物种和日期x物种相互作用术语，这表明生物标记物在日期或地点之间不同物种之间的变化不一致。尽管物种内和物种间存在这种差异，但生物标志物可以很容易地区分大型植物门。为了观察变化如何影响关于饮食的结论，我们使用贝叶斯混合模型来评估理论消费者在给定多样化饮食的情况下的情景，以及对其在不同地点和季节整合食物的方式的不同假设。模型运行的准确性(预测饮食与模拟饮食)随着生物标记物变量的数量增加而增加，并且强烈依赖于关于饮食的初始假设。当生物标记物的值基于仅从一个季节采样的大型植物，但消费者将多个季节的食物整合在一起时，准确率最低，这种情况在生物标记物文献中常见。与自然生物标记物变化减少对食物网络结构的洞察的概念相反，探索这种变化背后的潜在机制应该提供对沿海生态系统动态的更现实的看法。
Studies that use biomarkers to elucidate consumer diets often must assume that these signatures are relatively invariant in space and time. We tested this assumption for multiple stable isotopes (MSI: delta C-13, delta N-15, delta S-34) and fatty acids in 10 marine macrophytes (macroalgae and seagrass) on 3 different dates, and also quantified MSI at 3 sites in the coastal northeast Pacific. For all comparisons, we found significant variation in biomarkers among species, sites, and dates; furthermore, there were always significant site x species and date x species interaction terms, indicating that biomarkers do not change consistently across species among dates or sites. Despite this variation within and among species, biomarkers could readily distinguish macrophyte phyla. To observe how variation could affect conclusions about diets, we used a Bayesian mixing model to evaluate scenarios for a theoretical consumer given diverse diets, and with varying assumptions about the way it integrates foods over sites and seasons. Accuracy of the model runs (predicted diet versus simulated diet) increased with the number of biomarker variables, and depended strongly on initial assumptions about diets. The lowest accuracy occurred when biomarker values were based on macrophytes sampled only from 1 season but the consumer integrated foods across multiple seasons, a situation commonly seen in biomarker literature. Contrary to the notion that natural biomarker variation reduces insight into food web structure, exploring the potential mechanisms behind this variation should provide a more realistic view of coastal ecosystem dynamics.