Biogeosciences www.biogeosciences.net 1726-4170 1726-4189 5 4 2008 10.5194/bg-5-1165-2008 http://www.biogeosciences.net/5/1165/2008/ http://www.biogeosciences.net/5/1165/2008/bg-5-1165-2008.html http://www.biogeosciences.net/5/1165/2008/bg-5-1165-2008.pdf 1165 1173 2008-08-25 Distribution and bacterial availability of dissolved neutral sugars in the South East Pacific R. Sempéré richard.sempere@univmed.fr M. Tedetti C. Panagiotopoulos B. Charrière F. Van Wambeke Laboratoire de Microbiologie, Géochimie et Ecologie Marines (LMGEM), UMR 6117, CNRS, Université de la Méditerranée, Centre d'Océanologie de Marseille, Campus de Luminy, Case 901, 13 288 Marseille Cedex 9, France The distribution and bacterial availability of dissolved neutral sugars were studied in the South East Pacific from October to December 2004 during the BIOSOPE cruise. Four contrasting stations were investigated: Marquesas Islands (MAR), the hyper-oligotrophic South Pacific Gyre (GYR), the eastern part of the Gyre (EGY), and the coastal waters associated to the upwelling area off Chile (UPW). Total (free and combined) dissolved neutral sugar (TDNS) concentrations were in the same order of magnitude at MAR (387±293 nM), GYR (206±107 nM), EGY (269±175 nM), and UPW (231±73 nM), with the highest and lowest concentrations found at MAR (30 m, 890 nM) and EGY (250 m, 58 nM), respectively. Their contribution to dissolved organic carbon (TDNS-C×DOC^−1%) was generally low for all sites varying from 0.4% to 6.7% indicating that South East Pacific surface waters were relatively poor in neutral sugars. Free dissolved neutral sugar (FDNS; e.g. sugars analyzed without hydrolysis) concentrations were very low within the detection limit of our method (5–10 nM) accounting for <5% of the TDNS. In general, the predominant sugars within the TDNS pool were glucose, xylose, arabinose, and galactose, while in the FDNS pool only glucose was present. TDNS stock to bacterial production ratios (integrated values from the surface to the deep chlorophyll maximum) were high at GYR with respect to the low primary production, whereas the opposite trend was observed in the highly productive area of UPW. Intermediate situations were observed for MAR and EGY. Bioavailability of dissolved organic matter (DOM) exposed to natural solar radiation was also experimentally studied and compared to dark treatments. Our results showed no or little detectable effect of sunlight on DOM bacterial assimilation in surface waters of UPW and GYR, while a significant stimulation was found in MAR and EGY. The overall results clearly suggest that DOM is less labile at GYR compared to UPW, which is consistent with the observed accumulation of dissolved organic carbon and the elevated C/N ratios reported by Raimbault et al. (2008). Aluwihare, L. I., Repeta, D. J., and Chen, R. F.: A major biopolymeric component to dissolved organic carbon in seawater, Nature, 387, 166–167, 1997. Amon, R. M. W. and Benner, R.: Combined neutral sugar as indicators of the diagenetic state of dissolved organic matter in the Arctic Ocean, Deep-Sea Res. Pt. I, 50, 151–169, 2003. Blain, S., Bonnet, S., and Guieu, C.: Dissolved iron distribution in the tropical and sub tropical South Eastern Pacific, Biogeosciences, 5, 269–280, 2008. Benner, R. and Kaiser, K.: Abundance of amino sugars and peptidoglycan in marine particulate and dissolved organic matter, Limnol. Oceanogr., 48, 118–128, 2003. Benner, R., Pakulski, J. D., McCarthy, M., Hedges, J. I., and Hatcher, P. G.: Bulk chemical characteristics of dissolved organic matter in the ocean, Science, 255, 1562–1564, 1992. Benner, R.: Chemical composition and reactivity, in: Biogeochemistry of Marine Dissolved Organic Matter, edited by: Hansell, D. and Carlson, C., Academic Press, New York, USA, 59–90, 2002. Borch, N. H. and Kirchman, D. L.: Concentration and composition of dissolved combined neutral sugars (polysaccharides) in seawater determined by HPLC-PAD, Mar. Chem., 57, 85–95, 1997. Burney, C. M. and Sieburth, J. M.: Dissolved carbohydrates in seawater – II: A spectrometric procedure for total carbohydrate analysis and polysaccharide estimation, Mar. Chem., 5, 15–28, 1977. Carr, M. E.: Estimation of potential productivity in Eastern Boundary currents using remote sensing, Deep-Sea Res. Pt. II, 49, 59–80, 2002. Claustre, H. and Maritorena, S.: The many shades of ocean blue, Science, 302, 1514–1515, 2003. Claustre, H., Sciandra, A., and Vaulot, D.: Introduction to the special section bio-optical and biogeochemical conditions in the South East Pacific in late 2004: the BIOSOPE program, Biogeosciences, 5, 679–691, 2008. Kieber, R. J., Hydro, L. H, and Seaton, P. J.: Photooxydation of triglycerides and fatty acids in seawater: implication toward the formation of marine humic substances, Limnol. Oceanogr., 42, 1454–1462, 1997. Kieber, R. J., Zhou, X., and Mopper, K.: Formation of carbonyl compounds from UV-induced photodegradation of humic substances in natural waters: Fate of riverine carbon in the sea, Limnol. Oceanogr., 35, 1503–1515, 1990. Kirchman, D. L., Meon, B., Ducklow, H. W., Carlson, C. A., Hansell, D. A., and Steward, G.: Glucose fluxes and concentrations of dissolved combined sugars (polysaccharides) in the Ross Sea and Polar Front Zone, Antarctica, Deep-Sea Res. Pt. II, 48, 4179–4197, 2001. Mopper, K. and Kieber, D. J.: Photochemistry and the cycling of carbon, sulphur, nitrogen and phosphorus, in: Biogeochemistry of marine dissolved organic matter, edited by: Hansell, D. A. and Carlson, C. A., Academic Press, San Diego, CA, USA, 455–507, 2002. Mopper, K., Schultz, C., Chevolot, L., Germain, C., Revuelta, R., and Dawson, R.: Determination of sugars in unconcentrated seawater and other natural waters by liquid chromatography, Environ. Sci. Technol., 26, 133–137, 1992. Moran, M. A. and Covert, J. S.: Photochemically mediated linkages between dissolved organic matter and bacterioplankton, in: Aquatic ecosystems: interactivity of dissolved organic matter, edited by: Findlay, S. E. G. and Sinsabaugh, R. L., Academic Press, San Diego, CA, USA, 243–262, 2003. Moran, M. A. and Zepp, R. G.: Role of photoreactions in the formation of biologically labile compounds from dissolved organic matter, Limnol. Oceanogr., 42, 1307–1316, 1997. Morel, A., Gentili, B., Claustre, H., Babin, M., Bricaud, A., Ras, J., and Tieche F.: Optical properties of the "clearest" natural waters, Limnol. Oceanogr., 52, 217–229, 2007. Painter, T. J.: Algal polysaccharides, in: Polysaccharides, edited by: Aspinall, G. O., Academic, New York, USA, 195–285, 1983. Pakulski, J. and Benner, R.: Abundance and distribution of carbohydrates in the ocean, Limnol. Oceanogr., 39, 930–940, 1994. Panagiotopoulos, C. and Sempéré, R.: Molecular distribution of carbohydrates in large marine particles, Mar. Chem., 95, 31–49, 2005. Panagiotopoulos, C., Sempéré, R., Lafont, R., and Kerhervé, P.: Effects of temperature in the determination of monosaccharides by using an anion-exchange column, J. Chromatogr., 920, 13–22, 2001. Parsons, T. R., Takahashi, M., and Hargrave, B.: Biological oceanographic processes, Pergamon, Oxford, UK, 1984. Raimbault, P., Garcia, N., and Cerutti, F.: Distribution of inorganic and organic nutrients in the South Pacific Ocean – evidence for long-term accumulation of organic matter in nitrogen-depleted waters, Biogeosciences, 5, 281–298, 2008. Ras, J., Claustre, H., and Uitz, J.: Spatial variability of phytoplankton pigment distributions in the Subtropical South Pacific Ocean: comparison between in situ and predicted data, Biogeosciences, 5, 353–369, 2008. Rich, J. H., Ducklow, H. W., and Kirchman, D. L.: Concentrations and uptake of neutral monosaccharides along 140° W in the equatorial Pacific: contribution of glucose to heterothrophic bacterial activity and the DOM flux, Limnol. Oceanogr., 41, 595–604, 1996. Rich, J. H., Gosselin, M., Sherr, E., Sherr, B., and Kirchman, D. L.: High bacterial production, uptake and concentrations of dissolved organic matter in the central Arctic Ocean, Deep-Sea Res. Pt. II, 44, 1645–1663, 1997. Signorini, S. R., McClain, C. R., and Dandonneau, Y.: Mixing and phytoplankton bloom in the wake of the Marquesas Islands, Geophys. Res. Lett., 26, 3121–3124, 1999. Skoog, A. and Benner, R.: Aldoses in various size fractions of marine organic matter: Implications for carbon cycling, Limnol. Oceanogr., 42, 1803–1813, 1997. Skoog, A., Biddanda, B., and Benner, R.: Bacterial utilization of dissolved glucose in the upper water column of the Gulf of Mexico, Limnol. Oceanogr., 44, 1625–1633, 1999. Smith, D. C. and Azam, F.: A simple, economical method for measuring bacterial protein synthesis rates in sea water using 3H-Leucine, Mar. Microb. Food Webs, 6, 107–114, 1992. Stouthamer, A. H.: Energetic aspects of the growth of micro-organisms, Symp. Soc. Gen. Microbiol., 27, 285–315, 1977. Tedetti, M., Sempéré, R., Vasilkov, A., Charrière, B., Nérini, D., Miller, W. L., Kawamura, K., and Raimbault, P.: High penetration of ultraviolet radiation in the south east Pacific waters, Geophys. Res. Lett., 34, L12610, doi:10.1029/2007GL029823, 2007. Thingstad, T. F., Hagstrom, A., and Rassoulzadegan, F.: Accumulation of degradable DOC in surface waters: Is it caused by a malfunctioning microbial loop?, Limnol. Oceanogr., 42, 398–404, 1997. Van Wambeke, F., Bonnet, S., Moutin, T., Raimbault, P., Alarcón, G., and Guieu, C.: Factors limiting heterotrophic bacterial production in the southern Pacific Ocean, Biogeosciences, 5, 833–845, 2008. Van Wambeke, F., Obernosterer, I., Moutin, T., Duhamel, S., Ulloa, O., and Claustre, H.: Heterotrophic bacterial production in the South East Pacific: longitudinal trends and coupling with primary production, Biogeosciences, 5, 1–13, 2008a. Van Wambeke, F., Tedetti, M., Duhamel, S., and Sempéré, R.: Diel variability of heterotrophic bacterial production and UV doses in the South East Pacific, Biogeosciences Discuss., 5, 435–462, 2008b.