BGD Biogeosciences Discussions BGD 1810-6285 Copernicus GmbH Göttingen, Germany 10.5194/bgd-9-9571-2012 Dissolved organic matter composition and bioavailability reflect ecosystem productivity in the Western Arctic Ocean Shen Y. 1 Fichot C. G. 1 Benner R. 1 2 Marine Science Program, University of South Carolina, Columbia, South Carolina 29208, USA Department of Biological Sciences, University of South Carolina, Columbia, South Carolina 29208, USA 27 07 2012 9 7 9571 9601 This is an open-access article ditributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited. This article is available from http://www.biogeosciences-discuss.net/9/9571/2012/bgd-9-9571-2012.html The full text article is available as a PDF file from http://www.biogeosciences-discuss.net/9/9571/2012/bgd-9-9571-2012.pdf

Dissolved organic carbon (DOC) and total dissolved amino acids (TDAA) were measured in high (Chukchi Sea) and low (Beaufort Sea) productivity regions of the Western Arctic Ocean to investigate the composition and bioavailability of dissolved organic matter (DOM). Concentrations and DOC-normalized yields of TDAA in Chukchi surface waters were relatively high, indicating an accumulation of bioavailable DOM. High yields of TDAA were also observed in the upper halocline of slope and basin waters, indicating off-shelf transport of bioavailable DOM from the Chukchi Sea. In contrast, concentrations and yields of TDAA in Beaufort surface waters were relatively low, indicting DOM was of limited bioavailability. Yields of TDAA in the upper halocline of slope and basin waters were also low, suggesting the Beaufort is not a major source of bioavailable DOM to slope and basin waters. In shelf waters of both systems, elevated concentrations and yields of TDAA were often observed in waters with higher chlorophyll concentrations and productivity. Surface concentrations of DOC were similar (<i>p</i> > 0.05) in the two systems despite the contrasting productivity, but concentrations and yields of TDAA were significantly higher (<i>p</i> < 0.0001) in the Chukchi than in the Beaufort. Unlike bulk DOC, TDAA concentrations and yields reflect ecosystem productivity in the Western Arctic. The occurrence of elevated bioavailable DOM concentrations in the Chukchi implies an uncoupling between the biological production and utilization of DOM and has important implications for sustaining heterotrophic microbial growth and diversity in oligotrophic waters of the Central Arctic basins.

 References Amon,~R.: The role of dissolved organic matter for the organic carbon cycle in the Arctic Ocean, in: The Organic Carbon Cycle in the Arctic Ocean, edited by: Stein,~R. and Macdonald,~R., Springer-Verlag, Berlin, 83–99, 2004. Amon,~R M W., Fitznar,~H P., and Benner,~R.: Linkages among the bioreactivity, chemical composition, and diagenetic state of marine dissolved organic matter, Limnol. Oceanogr., 46, 287–297, 2001. Arrigo,~K R. and van Dijken,~G L.: Annual cycles of sea ice and phytoplankton in Cape Bathurst polynya, Southeastern Beaufort Sea, Canadian Arctic, Geophys. Res. Lett., 31, L08304, http://dx.doi.org/10.1029/2003GL018978doi:10.1029/2003GL018978, 2004. Azam,~F. and Malfatti,~F.: Microbial structuring of marine ecosystems, Nat. Rev. Microbiol., 5, 782–791, 2007. Bélanger,~S., Xie,~H X., Krotkov,~N., Larouche,~P., Vincent,~W F., and Babin,~M.: Photomineralization of terrigenous dissolved organic matter in Arctic coastal waters from 1979 to 2003: interannual variability and implications of climate change, Global Biogeochem. Cy., 20, GB4005, doi:http://dx.doi.org/10.1029/2006gb00270810.1029/2006gb002708, 2006. Benner,~R.: Molecular indicators of the bioavailability of dissolved organic matter, in: Aquatic Ecosystems: Interactivity of Dissolved Organic Matter, edited by: Findlay,~S. and Sinsabaugh,~R., Elsevier, Amsterdam, 121–137, 2003. Benner,~R. and Opsahl,~S.: Molecular indicators of the sources and transformations of dissolved organic matter in the Mississippi river plume, Org. Geochem., 32, 597–611, 2001. Brugel,~S., Nozais,~C., Poulin,~M., Tremblay,~J. É., Miller,~L A., Simpson,~K G., Gratton,~Y., and Demers,~S.: Phytoplankton biomass and production in the Southeastern Beaufort Sea in autumn 2002 and 2003, Mar. Ecol. Prog. Ser., 377, 63–77, 2009. Carmack,~E. and Wassmann,~P.: Food webs and physical-biological coupling on pan-Arctic shelves: unifying concepts and comprehensive perspectives, Prog. Oceanogr., 71, 446–477, 2006. Carmack,~E C., Macdonald,~R W., and Jasper,~S.: Phytoplankton productivity on the Canadian Shelf of the Beaufort Sea, Mar. Ecol. Prog. Ser., 277, 37–50, 2004. Cauwet,~G. and Sidorov,~I.: The biogeochemistry of Lena River: organic carbon and nutrients distribution, Mar. Chem., 53, 211–227, 1996. Chin-Leo,~G. and Benner,~R.: Enhanced bacterioplankton production and respiration at intermediate salinities in the Mississippi River plume, Mar. Ecol. Prog. Ser., 87, 87–103, 1992. Cooper,~L W., Benner,~R., McClelland,~J W., Peterson,~B J., Holmes,~R M., Raymond,~P A., Hansell,~D A., Grebmeier,~J M., and Codispoti,~L A.: Linkages among runoff, dissolved organic carbon, and the stable oxygen isotope composition of seawater and other water mass indicators in the Arctic Ocean, J. Geophys. Res.-Biogeosci., 110, G02013, doi:http://dx.doi.org/10.1029/2005jg00003110.1029/2005jg000031, 2005. Cota,~G., Pomeroy,~L., Harrison,~W., Jones,~E., Peters,~F., Sheldon,~W., and Weingartner,~T.: Nutrients, primary production and microbial heterotrophy in the Southeastern Chukchi Sea: Arctic summer nutrient depletion and heterotrophy, Mar. Ecol. Prog. Ser., 135, 247–258, 1996. Dagg,~M., Benner,~R., Lohrenz,~S., and Lawrence,~D.: Transformation of dissolved and particulate materials on continental shelves influenced by large rivers: plume processes, Cont. Shelf Res., 24, 833–858, 2004. Dauwe,~B., and Middelburg,~J J.: Amino acids and hexosamines as indicators of organic matter degradation state in North Sea sediments, Limnol. Oceanogr., 43, 782–798, 1998. Dauwe,~B., Middelburg,~J., Herman,~P., and Heip,~C.: Linking diagenetic alteration of amino acids and bulk organic matter reactivity, Limnol. Oceanogr., 44, 1809–1814, 1999. Davis,~J. and Benner,~R.: Seasonal trends in the abundance, composition and bioavailability of particulate and dissolved organic matter in the Chukchi/Beaufort Seas and Western Canada Basin, Deep-Sea Res. Pt~II, 52, 3396–3410, 2005. Davis,~J. and Benner,~R.: Quantitative estimates of labile and semi-labile dissolved organic carbon in the Western Arctic Ocean: a~molecular approach, Limnol. Oceanogr., 52, 2434–2444, 2007. Davis,~J., Kaiser,~K., and Benner,~R.: Amino acid and amino sugar yields and compositions as indicators of dissolved organic matter diagenesis, Org. Geochem., 40, 343–352, 2009. Emmerton,~C A., Lesack,~L F W., and Vincent,~W F.: Nutrient and organic matter patterns across the Mackenzie River, estuary and shelf during the seasonal recession of sea-ice, J. Mar. Syst., 74, 741–755, 2008. Forest,~A., Tremblay,~J.-É., Gratton,~Y., Martin,~J., Gagnon,~J., Darnis,~G., Sampei,~M., Fortier,~L., Ardyna,~M., Gosselin,~M., Hattori,~H., Nguyen,~D., Maranger,~R., Vaqué,~D., Marrasé,~C., Pedrós-Alió,~C., Sallon,~A., Michel,~C., Kellogg,~C., Deming,~J., Shadwick,~E., Thomas,~H., Link,~H., Archambault,~P., and Piepenburg,~D.: Biogenic carbon flows through the planktonic food web of the Amundsen Gulf (Arctic Ocean): a~synthesis of field measurements and inverse modeling analyses, Prog. Oceanogr., 91, 410–436, 2011. Garneau,~M \`E., Vincent,~W F., Alonso-Sáez,~L., Gratton,~Y., and Lovejoy,~C.: Prokaryotic community structure and heterotrophic production in a~river-influenced coastal arctic ecosystem, Aquat. Microb. Ecol., 42, 27–40, 2006. Grebmeier,~J M., Cooper,~L W., Feder,~H M., and Sirenko,~B I.: Ecosystem dynamics of the Pacific-influenced Northern Bering and Chukchi seas in the Amerasian Arctic, Prog. Oceanogr., 71, 331–361, 2006. Guéguen,~C., Guo,~L., and Tanaka,~N.: Distributions and characteristics of colored dissolved organic matter in the Western Arctic Ocean, Cont. Shelf Res., 25, 1195–1207, 2005. Hill,~V. and Cota,~G.: Spatial patterns of primary production on the shelf, slope and basin of the Western Arctic in 2002, Deep-Sea Res. Pt~II, 52, 3344–3354, 2005. Jakobsson,~M., Grantz,~A., Kristoffersen,~Y., and Macnab,~R.: The Arctic Ocean: boundary conditions and background information, in: The Organic Carbon Cycle in the Arctic Ocean, edited by: Stein,~R. and Macdonald,~R., Springer-Verlag, Berlin, 1–32, 2004. Juul-Pedersen,~T., Michel,~C., and Gosselin,~M.: Sinking export of particulate organic material from the euphotic zone in the Eastern Beaufort Sea, Mar. Ecol. Prog. Ser., 410, 55–70, 2010. Kaiser,~K. and Benner,~R.: Hydrolysis-induced racemization of amino acids, Limnol. Oceanogr.-Methods, 3, 318–325, 2005. Kaiser,~K. and Benner,~R.: Biochemical composition and size distribution of organic matter at the Pacific and Atlantic time-series stations, Mar. Chem., 113, 63–77, 2009. Kattner,~G., Lobbes,~J M., Fitznar,~H P., Engbrodt,~R., Nöthig,~E M., and Lara,~R J.: Tracing dissolved organic substances and nutrients from the Lena River through Laptev Sea (Arctic), Mar. Chem., 65, 25–39, 1999. Kellogg,~C T E., Carpenter,~S D., Renfro,~A A., Sallon,~A., Michel,~C., Cochran,~J K., and Deming,~J W.: Evidence for microbial attenuation of particle flux in the Amundsen Gulf and Beaufort Sea: elevated hydrolytic enzyme activity on sinking aggregates, Polar Biol., 34, 2007–2023, 2011. Kirchman,~D L., Hill,~V., Cottrell,~M T., Gradinger,~R., Malmstrom,~R R., and Parker,~A.: Standing stocks, production, and respiration of phytoplankton and heterotrophic bacteria in the Western Arctic Ocean, Deep-Sea Res. Pt II, 56, 1237–1248, 2009a. Kirchman,~D L., Morán,~X A G., and Ducklow,~H.: Microbial growth in the polar oceans – role of temperature and potential impact of climate change, Nat. Rev. Microbiol., 7, 451–459, 2009b. Lavoie,~D., MacDonald,~R W., and Denman,~K L.: Primary productivity and export fluxes on the Canadian shelf of the Beaufort Sea: a~modelling study, J. Mar. Syst., 75, 17–32, 2009. Macdonald,~R W., Wong,~C., and Erickson,~P.: The distribution of nutrients in the Southeastern Beaufort Sea: implications for water circulation and primary production, J. Geophys. Res., 92, 2939–2952, 1987. Macdonald,~R W., Solomon,~S M., Cranston,~R E., Welch,~H E., Yunker,~M B., and Gobeil,~C.: A~sediment and organic carbon budget for the Canadian Beaufort Shelf, Mar. Geol., 144, 255–273, 1998. Manley,~T. and Hunkins,~K.: Mesoscale eddies of the Arctic Ocean, J. Geophys. Res., 90, 4911–4930, 1985. Mathis,~J T., Hansell,~D A., and Bates,~N R.: Strong hydrographic controls on spatial and seasonal variability of dissolved organic carbon in the Chukchi Sea, Deep-Sea Res. Pt. II, 52, 3245–3258, 2005. Mathis,~J T., Pickart,~R S., Hansell,~D A., Kadko,~D., and Bates,~N R.: Eddy transport of organic carbon and nutrients from the Chukchi Shelf: Impact on the upper halocline of the Western Arctic Ocean, J. Geophys. Res.-Oceans, 112, C05011, http://dx.doi.org/10.1029/2006JC003899doi:10.1029/2006JC003899, 2007. Pomeroy,~L R. and Deibel,~D.: Temperature regulation of bacterial activity during the spring bloom in Newfoundland coastal waters, Science, 233, 359–361, 1986. Retamal,~L., Vincent,~W F., Martineau,~C., and Osburn,~C L.: Comparison of the optical properties of dissolved organic matter in two river-influenced coastal regions of the Canadian Arctic, Estuar. Coast. Shelf Sci., 72, 261–272, 2007. Retamal,~L., Bonilla,~S., and Vincent,~W F.: Optical gradients and phytoplankton production in the Mackenzie River and the coastal Beaufort Sea, Polar Biol., 31, 363–379, 2008. Sakshaug,~E.: Primary and secondary production in the Arctic seas, in: The Organic Carbon Cycle in the Arctic Ocean, edited by: Stein,~R. and Macdonald,~R., Springer-Verlag, Berlin, 57–81, 2004. Sallon,~A., Michel,~C., and Gosselin,~M.: Summertime primary production and carbon export in the Southeastern Beaufort Sea during the low ice year of 2008, Polar Biol., 34, 1989–2005, 2011. Spall,~M A., Pickart,~R S., Fratantoni,~P S., and Plueddemann,~A J.: Western Arctic shelfbreak eddies: formation and transport, J Phys. Oceanogr., 38, 1644–1668, 2008. Springer,~A M. and McRoy,~C P.: The paradox of pelagic food webs in the Northern Bering Sea – III. Patterns of primary production, Cont. Shelf Res., 13, 575–599, 1993. Uher,~G., Hughes,~C., Henry,~G., and Upstill-Goddard,~R C.: Non-conservative mixing behavior of colored dissolved organic matter in a~humic-rich, turbid estuary, Geophys. Res. Lett., 28, 3309–3312, 2001. Wallace,~D W R., Moore,~R M., and Jones,~E P.: Ventilation of the Arctic Ocean cold halocline: rates of diapycnal and isopycnal transport, oxygen utilization and primary production inferred using chlorofluoromethane distributions, Deep-Sea Res. Pt I, 34, 1957–1979, 1987. Walsh,~J J., McRoy,~C P., Coachman,~L K., Goering,~J J., Nihoul,~J J., Whitledge,~T E., Blackburn,~T H., Parker,~P L., Wirick,~C D., Shuert,~P G., Grebmeier,~J M., Springer,~A M., Tripp,~R D., Hansell,~D A., Djenidi,~S., Deleersnijder,~E., Henriksen,~K., Lund,~B A., Andersen,~P., Mullerkarger,~F E., and Dean,~K.: Carbon and nitrogen cycling within the Bering/Chukchi Seas: source regions for organic matter effecting AOU demands of the Arctic Ocean, Prog. Oceanogr., 22, 277–359, 1989. Walsh,~J J., Dieterle,~D A., Muller-Karger,~F E., Aagaard,~K., Roach,~A T., Whitledge,~T E., and Stockwell,~D.: CO<sub>2</sub> cycling in the coastal ocean. II. Seasonal organic loading of the Arctic Ocean from source waters in the Bering Sea, Cont. Shelf Res., 17, 1–36, 1997. Wheeler,~P A., Watkins,~J M., and Hansing,~R L.: Nutrients, organic carbon and organic nitrogen in the upper water column of the Arctic Ocean: implications for the sources of dissolved organic carbon, Deep-Sea Res. Pt II, 44, 1571–1592, 1997.