A novel approach using the ¹⁵N tracer technique and benthic chambers to determine ammonium fluxes at the sediment-water interface and its application in a back-reef zone on Reunion Island (Indian Ocean)

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• 作者：St茅phane L'Helguen ; Laurent Chauvaud ; Pascale Cuet ; Patrick Frouin ; Jean-Fran莽ois Maguer ; Jacques Clavier
• 关键词：15N tracer ; Ammonium fluxes ; Benthic chamber ; Coral reef ; Sediment&ndash ; water interface
• 刊名：Journal of Experimental Marine Biology and Ecology
• 出版年：March, 2014
• 年：2014
• 卷：452
• 期：Complete
• 页码：143-151
• 全文大小：438 K

文摘

The ¹⁵N tracer method and the benthic chamber technique were combined to evaluate NH₄⁺ exchanges at the sediment-water interface. This novel approach consists in measuring NH₄⁺ fluxes during a single in situ incubation in a sample of water enclosed in a benthic chamber placed over the sediment and in a subsample thereof concomitantly incubated in a bottle. Using this combined approach, the influx and efflux of NH₄⁺ across the sediment-water interface can be simultaneously measured along with uptake and regeneration rates of NH₄⁺ in the water column. Details of the experimental protocol and principles behind the calculations of N transport rates are given. We applied this approach to a tropical reef on Reunion Island (Indian Ocean). Experiments were carried out in triplicate at three stations with organic-poor, sandy sediments. At the three stations, the mean flux of NH₄⁺ from the water column to the sediment (29.6-59.2 渭mol m^鈭?#xA0;2 h^鈭?#xA0;1) was much higher than the mean NH₄⁺ uptake rate by phytoplankton (3.0-4.0 渭mol m^鈭?#xA0;2 h^鈭?#xA0;1) indicating that the removal of NH₄⁺ from the water column must be due, for the most part, to uptake by benthic microalgae in the study area. The mean flux of NH₄⁺ from the sediment to the water column (6.7-13.7 渭mol m^鈭?#xA0;2 h^鈭?#xA0;1) was comparable to the mean regeneration rate in the water (7.4-9.9 渭mol m^鈭?#xA0;2 h^鈭?#xA0;1) suggesting that the sediment may constitute a significant N source for phytoplankton in the back-reef zone on Reunion Island.