Sediment community responses to marine vs. terrigenous organic matter in a submarine canyon
Sediment community responses to marine vs. terrigenous organic matter in a submarine canyon
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DOI：
10.5194/bg-10-67-2013
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发表时间：
2013-01-01
期刊：
影响因子：
4.9
通讯作者：
Witte, U.
中科院分区：
文献类型：
--
作者：
Hunter, W. R.;Jamieson, A.;Witte, U.
惠塔德峡谷是凯尔特大陆边缘的一个分支海底峡谷，它可能是沉积物和有机质（OM）从欧洲大陆斜坡运输到深海海底的管道。在Whittard峡谷的东西分支进行了原位稳定同位素标记实验，测试了沉积物群落对富氮海生（Thalassiosira weissflogii）和贫氮陆生（Triticum aestivum）植物碎屑沉积的短期（3-7天）响应。C-13和N-15标记被追踪到动物生物量和沉积物中，C-13标记被追踪到细菌极性脂质脂肪酸（PLFAs）中。同位素标记穿透到5厘米的沉积物深度，在站点或实验处理（基质或时间）之间没有差异。峡谷东部和西部分支的大型动物组合结构存在差异。在海洋植物碎屑沉积后，大型动物的摄食活动在东西部分支之间没有变化，在3 ~ 7 d之间变化不大。陆源植物碎屑沉积后，大型动物对碳和氮的吸收显著降低，摄食活动受强烈的氮需求支配。细菌对C的摄取在惠塔德峡谷西部支流最大，但摄食活性在3 ~ 7 d之间下降。海洋和陆源有机质的细菌加工过程与表层（0-1 cm）沉积物中的大型动物群相似。然而，在较深的沉积物中，细菌利用了更大比例的陆源有机质。植物碎屑沉积后细菌生物量下降，与大型动物摄食活动呈负相关。因此，本研究表明，大型动物-细菌相互作用影响了惠塔德峡谷的底栖生物C循环，导致海洋和陆源OM的不同命运。
The Whittard Canyon is a branching submarine canyon on the Celtic continental margin, which may act as a conduit for sediment and organic matter (OM) transport from the European continental slope to the abyssal sea floor. In situ stable-isotope labelling experiments were conducted in the eastern and western branches of the Whittard Canyon, testing short-term (3-7 days) responses of sediment communities to deposition of nitrogen-rich marine (Thalassiosira weissflogii) and nitrogen-poor terrigenous (Triticum aestivum) phytodetritus. C-13 and N-15 labels were traced into faunal biomass and bulk sediments, and the C-13 label traced into bacterial polar lipid fatty acids (PLFAs). Isotopic labels penetrated to 5 cm sediment depth, with no differences between stations or experimental treatments (substrate or time). Macrofaunal assemblage structure differed between the eastern and western canyon branches. Following deposition of marine phytodetritus, no changes in macrofaunal feeding activity were observed between the eastern and western branches, with little change between 3 and 7 days. Macrofaunal C and N uptake was substantially lower following deposition of terrigenous phytodetritus with feeding activity governed by a strong N demand. Bacterial C uptake was greatest in the western branch of the Whittard Canyon, but feeding activity decreased between 3 and 7 days. Bacterial processing of marine and terrigenous OM were similar to the macrofauna in surficial (0-1 cm) sediments. However, in deeper sediments bacteria utilised greater proportions of terrigenous OM. Bacterial biomass decreased following phytodetritus deposition and was negatively correlated to macrofaunal feeding activity. Consequently, this study suggests that macrofaunal-bacterial interactions influence benthic C cycling in the Whittard Canyon, resulting in differential fates for marine and terrigenous OM.