Braeckman Ulrike, Provoost Pieter, Sabbe Koen, Soetaert Karline, Middelburg Jack J, Vincx Magda, Vanaverbeke Jan
Ghent University, Department of Biology, Marine Biology Research Group, Krijgslaan 281/S8, 9000 Ghent, Belgium.
Royal NIOZ Yerseke, Centre for Estuarine and Marine Ecology, PO Box 140, 4400 AC Yerseke, The Netherlands.
Mar Environ Res. 2015 Jul;108:55-68. doi: 10.1016/j.marenvres.2015.04.010. Epub 2015 Apr 28.
We investigated the temporal variation of pelagic and benthic food sources in the diet of benthic taxa at a depositional site in the Southern Bight of the North Sea by means of fatty acid (FA) biomarkers and compound-specific stable isotope analysis (CSIA). The taxa were the non-selective deposit feeding nematodes (Sabatieria spp. and 'other nematodes'), and three dominant macrobenthic species: two true suspension-deposit feeders (the bivalve Abra alba and the tube dwelling polychaete Owenia fusiformis) and the suspected predatory mud-dwelling anemone Sagartia sp. These species make up on average 16% (Abra alba), 17% (Sagartia sp.) and 20% (Owenia fusiformis) of the biomass in the Abra alba-Kurtiella bidentata community in this area. Phytoplankton dynamics in the suspended particulate matter of the water column as inferred from cell counts, chlorophyll-a and organic carbon content were clearly visible in sediment and animal FA abundance as well, whereas phytodetritus dynamics in the sediment FA composition were less clear, probably due to patchy distribution or stripping of FA by macrofauna. Nematodes appeared to assimilate mainly Polyunsaturated Fatty Acids (PUFAs) from their sedimentary environment and were further non-selectively accumulating more (Sabatieria spp.) or less ('other nematodes') FA from the deposited phytodetritus. In contrast, Abra alba FA composition was consistent with a diatom-dominated diet and consumption of Phaeocystis was observed in Owenia fusiformis, whereas Sagartia sp. showed evidence of a predatory behaviour. While the total FA content in Owenia fusiformis remained constant throughout the year, Sagartia sp. doubled and Abra alba increased its FA level more than 10-fold in response to the organic matter deposition from the phytoplankton bloom. This leads to the conclusion that there is no resource partitioning between non-selective deposit feeding nematodes and the suspension-deposit feeding macrobenthic organisms, suggesting they belong to separate parts of the benthic food web.
我们通过脂肪酸（FA）生物标志物和化合物特异性稳定同位素分析（CSIA），研究了北海南部浅滩一个沉积位点底栖生物类群饮食中浮游和底栖食物来源的时间变化。这些生物类群包括非选择性沉积取食的线虫（萨巴蒂埃线虫属和“其他线虫”），以及三种优势大型底栖生物：两种真正的悬浮沉积取食者（双壳类白樱蛤和管栖多毛类纺锤欧文蚓）和疑似捕食性泥栖海葵萨氏海葵属。在该区域的白樱蛤 - 双齿库氏虫群落中，这些物种的生物量平均分别占16%（白樱蛤）、17%（萨氏海葵属）和20%（纺锤欧文蚓）。从细胞计数、叶绿素a和有机碳含量推断出的水柱悬浮颗粒物中的浮游植物动态，在沉积物和动物脂肪酸丰度中也清晰可见，而沉积物脂肪酸组成中的植物碎屑动态则不太明显，可能是由于分布不均或大型动物对脂肪酸的去除。线虫似乎主要从其沉积环境中同化多不饱和脂肪酸（PUFA），并进一步非选择性地从沉积的植物碎屑中积累更多（萨巴蒂埃线虫属）或更少（“其他线虫”）的脂肪酸。相比之下，白樱蛤的脂肪酸组成与以硅藻为主的饮食一致，在纺锤欧文蚓中观察到其摄食了棕囊藻，而萨氏海葵属则表现出捕食行为的证据。虽然纺锤欧文蚓中的总脂肪酸含量全年保持恒定，但萨氏海葵属的脂肪酸含量翻倍，白樱蛤的脂肪酸水平因浮游植物大量繁殖带来的有机物沉积而增加了10倍以上。由此得出结论，非选择性沉积取食的线虫与悬浮沉积取食的大型底栖生物之间不存在资源分配，这表明它们属于底栖食物网的不同部分。
