Macrofaunal processing of phytodetritus at two sites on the Carolina margin:: in situ experiments using 13C-labeled diatoms
Macrofaunal processing of phytodetritus at two sites on the Carolina margin:: in situ experiments using 13C-labeled diatoms
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DOI：
10.3354/meps182037
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发表时间：
1999-01-01
影响因子：
2.5
通讯作者：
Thomas, CJ
中科院分区：
文献类型：
--
作者：
Levin, LA;Blair, NE;Thomas, CJ
在美国北卡罗来纳州的两个海拔850 m的地点（I号和III号），用C-13标记的硅藻海链藻进行了示踪实验，以研究大型底栖动物对新鲜植物碎屑的消耗模式。实验研究了沉积物柱内的分类，喂养方式，身体大小和垂直位置对获得表层有机质的影响。对来自背景沉积物和沉积物样地的大型底栖后生动物和凝集原生动物进行了δ（13）C测量，在沉积物样地中沉积了C-13标记的硅藻，然后在0.3 h、1 - 1.5 d、3 mo和14 mo后取样。在沉积物、后生动物和大型凝集原生动物的背景δ（13）C特征中观察到了站点间的显著差异，站点III的δ（13）C值比站点I低2 ~ 3 ppm。背景三角洲（13）C签名也不同的功能分类和垂直位置的沉积物柱在网站III。在Ⅰ类环节动物中，肉食动物的背景δ（13）C值高于表层沉积动物，但在Ⅲ类环节动物中没有观察到摄食组间的差异。短期（1至1.5天）实验的δ（13）C数据显示硅藻的快速摄食，主要是在站点I被凝集原生动物和环节动物摄食，在站点III主要被环节动物摄食。对硅藻的选择性摄食表现为paraonid多毛类，特别是Aricidea spp。在马尔丹的Praxillella sp.中也观察到硅藻C的异常高的吸收和保留，沙蚕Ceratocephale sp.和其他几种以沉积物为食的多毛类。14个月后，很少的硅藻C-13仍然在网站III，但高浓度的示踪剂存在于环节动物和凝集原生动物在网站I。在这两个网站，nonannelid后生动物和次表层沉积物喂养环节动物表现出最少的吸收和保留硅藻C。我们的假设，即大型生物类群和浅居的底栖动物应该有最大的机会获得新鲜沉积的有机物质没有得到证实。一些小的，深居的类群收购标签比大或近表面的形式更容易。示踪剂命运的网站之间的差异反映了更大的垂直混合在网站III。这些结果表明，在底栖过程的异质性沿着卡罗莱纳边缘。但表明不稳定的有机物在这两个地点都被迅速消耗。因为大多数的类群发现消费新鲜沉积的硅藻在这些实验中是典型的半深海设置，我们推断，植物碎屑到达海底边缘环境中的原生动物和后生动物的组成部分的底栖动物迅速处理。
Tracer experiments using C-13-labeled diatoms Thalassiosira pseudonana were carried out at two 850 m sites (I off Cape Fear and III off Cape Hatteras) on the North Carolina, USA, slope to examine patterns of macrofaunal consumption of fresh phytodetritus. Experiments examined the influence of taxon, feeding mode, body size and vertical position within the sediment column on access to surficial organic matter. delta(13)C measurements were made on macrofaunal metazoans and agglutinating protozoans from background sediments and from sediment plots in which C-13-labeled diatoms were deposited and then sampled 0.3 h, 1 to 1.5 d, 3 mo and 14 mo later. Significant between-site differences were observed in background delta(13)C signatures of sediments, metazoans, and large, agglutinating protozoans, with values 2 to 3 parts per thousand lower at Site III than at Site I. Background delta(13)C signatures also varied as a function of taxon and of vertical position in the sediment column at Site III. The background delta(13)C value of carnivores was higher than that of surface-deposit feeders among Site I annelids, but no annelid feeding-group differences were observed at Site III. delta(13)C data from short-term (1 to 1.5 d) experiments revealed rapid diatom ingestion, primarily by agglutinated protozoans and annelids at Site I and mainly by annelids at Site III. Selective feeding on diatoms was exhibited by paraonid polychaetes, especially Aricidea spp. Exceptionally high uptake and retention of diatom C also was observed in the maldanid Praxillella sp., the nereid Ceratocephale sp. and several other surface-deposit feeding polychaetes. After 14 mo, little of the diatom C-13 remained at Site III, but high concentrations of the tracer were present in annelids and agglutinating protozoans at Site I. At both sites, nonannelid metazoans and subsurface-deposit feeding annelids exhibited the least uptake and retention of diatom C. Our hypotheses that large-bodied taxa and shallow-dwelling infauna should have greatest access to freshly deposited organic matter were not borne out. Some small, deep-dwelling taxa acquired label more readily than large or near-surface forms. Differences in tracer fates between sites reflected greater vertical mixing at Site III. These results indicate heterogeneity in benthic processes along the Carolina margin. but suggest that labile organic matter is consumed quickly at both sites. Because most of the taxa found to consume freshly deposited diatoms in these experiments are typical of bathyal settings, we infer that phytodetritus reaching the seabed in margin environments is rapidly processed by protozoan and metazoan components of the benthic fauna.