The effect of acidification on the determination of organic carbon, total nitrogen and their stable isotopic composition in algae and marine sediment.

We investigated the effects of sample acidification on the stable carbon and nitrogen isotopic composition (delta13C and delta15N), as well as the organic carbon (OC) and total nitrogen (TN) composition, of an algal culture and a marine sediment. Replicate measurements of untreated and acid-treated samples were made using 1 M, 2 M and 6 M HCl, 6% H2SO3 and 1 M H3PO4. For all treatments the precision of the analysis for the acid-treated sample was equal to or less than that in the non-acidified sample. For the algae, analysis of variance (ANOVA) indicated no significant differences in the mean OC and TN concentration, or delta13C and delta15N composition, between any acid treatment and non-acidified samples. For the sediment sample a comparison could only be made between the different acid treatments because the untreated contained significant amounts ( approximately 30%) of carbonate carbon. ANOVA indicated that the mean OC determined in sediment samples after the 1 M HCl treatment and the mean delta13C values after the 6% H2SO3 and 1 M H3PO4 treatments were significantly different (p < 0.013 and < .05, respectively) from all other treatments. Mass balance calculations indicate that in some instances delta13C values were biased due to a contribution from unreacted carbonate carbon. There were no significant differences in the mean TN between any acid-treated and non-acidified samples. The mean delta15N values after 6 M HCl, 6% H2SO3 and 1 M H3PO4 treatments were significantly different from the untreated sediment sample (p < 0.044). Based on the significant bias observed for the delta15N and delta13C values, a weak (1-2 M) HCl solution is confirmed as the most appropriate acid for the removal of inorganic carbon from natural materials requiring elemental and isotopic analysis.

[1]  A. Lorrain,et al.  Decarbonation and preservation method for the analysis of organic C and N contents and stable isotope ratios of low-carbonated suspended particulate material , 2003 .

[2]  F. Grousset,et al.  Sources of fine-sized organic matter in North Atlantic Heinrich Layers: δ13C and δ15N tracers , 2002 .

[3]  C. Schubert,et al.  Nitrogen and carbon isotopic composition of marine and terrestrial organic matter in Arctic Ocean sediments:: implications for nutrient utilization and organic matter composition , 2001 .

[4]  C. Schubert,et al.  Effects of decarbonation treatments on δ13C values in marine sediments , 2000 .

[5]  J. Bouquegneau,et al.  Relative impact of a seagrass bed and its adjacent epilithic algal community in consumer diets , 2000 .

[6]  W. Helder,et al.  Carbonate removal by acidification causes loss of nitrogenous compounds in continental margin sediments , 2000 .

[7]  Keith L. Bosley,et al.  Effects of preservatives and acidification on the stable isotope ratios (15N :14N, 13C :12C) of two species of marine animals , 1999 .

[8]  J. Chanton,et al.  Plankton and dissolved inorganic carbon isotopic composition in a river-dominated estuary: Apalachicola Bay, Florida , 1999 .

[9]  J. Pinnegar,et al.  Differential fractionation of δ13C and δ15N among fish tissues: implications for the study of trophic interactions , 1999 .

[10]  T. Jickells,et al.  Analysis of total and organic carbon and total nitrogen in settling oceanic particles and a marine sediment: an interlaboratory comparison , 1998 .

[11]  N. Loneragan,et al.  Effects of acid washing on stable isotope ratios of C and N in penaeid shrimp and seagrass: Implications for food-web studies using multiple stable isotopes , 1995 .

[12]  T. Jickells,et al.  Temporal and spatial variability of biogenic particles fluxes during the JGOFS northeast Atlantic process studies at 47°N, 20°W , 1994 .

[13]  P. Erftemeijer,et al.  Pretreatment artefacts associated with the removal of calcareous epiphytes from seagrass leaves , 1994 .

[14]  J. Middelburg,et al.  Rapid analysis of organic carbon and nitrogen in particulate materials , 1994 .

[15]  J. Goering,et al.  Seasonal variability of stable carbon and nitrogen isotope ratios of organisms in a North Pacific Bay , 1990 .

[16]  P. Froelich.  Analysis of organic carbon in marine sediments1 , 1980 .

[17]  S. Waldron,et al.  The impact of sewage discharge in a marine embayment : A stable isotope reconnaissance , 2001 .

[18]  A. Fogg.  Editorial. The ‘new’ Analytical Proceedings , 1994 .

[19]  M. Fogel,et al.  Isotope Fractionation during Primary Production , 1993 .

[20]  A. Mcintyre,et al.  Determination of organic carbon and nitrogen in marine sediments using the Carlo Erba NA-1500 analyzer , 1990 .