Ingestion of 15N2-labelled Trichodesmium spp. and ammonium regeneration by the harpacticoid copepod Macrosetella gracilis
Ingestion of 15N2-labelled Trichodesmium spp. and ammonium regeneration by the harpacticoid copepod Macrosetella gracilis
复制标题
摄入 15N2 标记的 Trichodesmium spp.
DOI：
--
复制
发表时间：
1996
期刊：
影响因子：
--
通讯作者：
P. Glibert
中科院分区：
文献类型：
--
作者：
J. O'Neil;P. Metzler;P. Glibert
大洋性硬足类桡足类动物Macrosetella gracilis（A. Scott），被发现与固氮（重氮营养）、开花蓝细菌Trichodesmium spp的菌落有关。在热带和亚热带沃茨。M. gracilis是这些通常有毒的蓝细菌的少数直接食草动物之一。对M. 1992年9月在加勒比海和1994年11月在澳大利亚珊瑚海进行了gracilis试验。M. gracilis摄食Trichodesmium thiebautii标记的15 N2在东加勒比测量表明，M.薄肌可消耗总T的33 ~ 45%。thiebautii群体N d ~（-1）和>100%的新氮固定d ~（-1）。同时测定了M. gracilis取食T. thiebautii，以及非喂养桡足类，使用15 N同位素稀释法。在非摄食桡足类中，NH+4释放速率随着桡足类数量和食物供应量的增加而增加。在T. thiebautii colonies、M.在无食物的条件下，NH 4+的平均再生速率为7.7±1.5 nmolN-1 h-1（±SE），显著高于无食物时的1.9±0.7 nmolN-1 h-1（±SE）。M.基于排泄：摄入比率，gracilis的排泄相对较高，这可能是由于容易获得高N食物源，“草率进食”效应，或作为对蓝细菌中毒素的反应。M. gracilis和T.芦苇导致显着增加[NH+4]作为桡足类密度的函数。从蓝藻和/或微异养联营体的铵泄漏是相对较低的。M. gracilis，通过排泄和可能的机械破碎的细胞，而放牧，似乎提供了一个直接的联系大气来源的“新”氮和再生NH+4在贫营养系统中，束毛藻属。是丰富的。
The pelagic harpacticoid copepod, Macrosetella gracilis (A. Scott), is found in association with colonies of the nitrogen-fixing (diazotrophic), bloomforming cyanobacterium Trichodesmium spp. in tropical and subtropical waters. M. gracilis is one of the few direct grazers of these often toxic cyanobacteria. Experiments investigating NH+4regeneration by M. gracilis were conducted in the Caribbean in September 1992 and the Coral Sea, Australia in November 1994. Rates of M. gracilis ingestion of Trichodesmium thiebautii labelled with 15N2 measured in the eastern Caribbean indicated that M. gracilis could consume 33 to 45% of total T. thiebautii colony N d-1 and >100% of new N fixed d-1. We also measured the release of NH+4by M. gracilis feeding on T. thiebautii, as well as by non-feeding copepods, using 15N isotope dilution methods. In non-feeding copepods, rates of NH+4release increased as numbers of copepods were increased as both copepod numbers and food availability increased. In the presence of T. thiebautii colonies, M. gracilis had an average rate of NH+4regeneration of 7.7±1.5 nmol N copepod-1 h-1 (±SE), which was significantly higher than when food was absent (1.9±0.7 nmol N copepod-1 h-1). Rates of M. gracilis excretion were relatively high based on excretion: ingestion ratios, which could be due to having a high-N food source readily available, to “sloppy-feeding” effects, or as a response to toxins in the cyanobacterium. Incubations of M. gracilis with and without T. erythraeum resulted in significant increases in [NH+4] as a function of copepod density only. Ammonium leakage from the cyanobacterium and/or microheterotroph associates was relatively low. M. gracilis, through excretion and possible mechanical breakage of cells while grazing, appears to provide a direct link between atmospherically derived “new” nitrogen and regenerated NH+4in the oligotrophic systems where Trichodesmium spp. are abundant.