ABSTRACT: Consumer tissue stable carbon isotope compositions (δ¹³C) are well established indicators of benthic and pelagic foraging in marine ecosystems. Stable sulfur isotope compositions (δ³⁴S) are also potentially useful in this regard but have not been widely utilized outside of estuaries and salt marsh ecosystems. To test the ability of δ¹³C and δ³⁴S to reflect benthic and pelagic foraging, we analyzed the stable carbon, nitrogen (δ¹⁵N), and sulfur isotope compositions of bone collagen from walrus (an obligate benthic feeder) and ringed seal (a mixed benthic/pelagic feeder) sampled from across the North American Arctic. Both had relatively low δ³⁴S values compared to those typically observed in marine consumers. These data suggest an important role for benthic microalgae in coastal marine food webs in the Arctic. At all of the 10 locations where both taxa could be sampled, walrus had lower δ³⁴S values than ringed seal, suggesting that this measurement is a useful indicator of benthic and pelagic foraging in nearshore Arctic environments. Contrary to expectations, there were no consistent differences in δ¹³C between walrus and ringed seal at any of these sites, suggesting that this measurement may not always be best interpreted in light of benthic vs. pelagic foraging, particularly when comparisons are made across trophic levels. When the foraging ecology of a consumer is unknown, our data suggest that δ³⁴S may be a more sensitive indicator of the relative importance of benthic and pelagic prey in the diet than δ¹³C.

中文翻译：

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北极海洋哺乳动物中的硫同位素（δ34S）：底栖与中上层觅食指标

摘要：消费者组织稳定的碳同位素组合物（δ ¹³ C）在海洋生态系统已经很好地建立底栖和浮游觅食的指标。稳定硫同位素组合物（δ ³⁴ S），可以在这方面可能有用的，但还没有被广泛使用河口和盐沼生态系统的外部。为了测试的δ的能力¹³ C和δ ³⁴秒至反映底栖和浮游觅食，我们分析了稳定的碳，氮（δ ¹⁵ N），并且从海象骨胶原（专性底栖进料器）和环斑密封的硫同位素组成（底栖动物/浮游生物混合饲养者）从整个北美北极地区采样。既具有相对低的δ ³⁴与海洋消费者中通常观察到的S值相比。这些数据表明底栖微藻在北极沿海海洋食物网中具有重要作用。在所有10个位置其中两个类群进行采样的，海象具有较低的δ ^34个价值观比环状密封，这表明该测量是在近岸北极环境底栖和浮游觅食的一个有用的指标。与预期相反，有在无δ一致的差异¹³在任意站点的海象和环斑密封件之间C，这表明该测量可能不总是最好在光的底栖与浮游觅食，解释特别是当比较跨营养制成水平。当消费者的觅食生态是未知的，我们的数据表明，δ ³⁴S可以是在饮食比δ的海底和浮游猎物的相对重要性更敏感的指示器¹³ C.