Dissolved organic matter assimilation by heterotrophic bacterial groups in the western Arctic Ocean

Abstract

Abundance of the major bacterial groups and dissolved organic matter (DOM) assimilation in the western Arctic Ocean were determined using fluorescence in situ hybridization (FISH) and microautoradiography combined with FISH (Micro-FISH). Cytophaga-like bacteria (25 to 65%) and Alphaproteobacteria (17 to 40%) were the dominant bacterial groups, followed by Gammaproteobacteria (10 to 30%). In contrast, Betaproteobacteria and Actinobacteria were never abundant. While the distribution of Alphaproteobacteria was relatively uniform along a transect from the shelf to the basin, Cytophaga-like bacteria were more abundant on the shelf and shelf-break. Similarly, the contribution to DOM assimilation by Cytophaga-like bacteria was highest on the shelf and lowest in the basin. In contrast, Alphaproteobacteria contributed the most to DOM assimilation at the slope. About 80 to 99% of the variation in DOM assimilation was explained by bacterial group abundance. As a whole, the prokaryotic community was most active in assimilating free amino acids (50 to 60%), followed by diatom-derived extracellular polymers (30 to 40%) and protein (20 to 30%). In contrast, relatively few cells assimilated glucose (10 to 20%). This study revealed substantial variation in the abundance of major bacterial groups among the Arctic regions and in the assimilation of DOM components by these bacteria. KEY WORDS: DOM assimilation · Arctic Ocean · Micro-FISH · Heterotrophic bacteria Resale or republication not permitted without written consent of the publisherAquat Microb Ecol 50: [39][40][41][42][43][44][45][46][47][48][49] 2007 overestimate the true activity. In the western Arctic Ocean, up to 60 and 45% of bacteria and archaea, respectively, assimilated various DOM compounds ). Other data suggest that up to 84% of total prokaryotes are active in reducing 5-cyano-2, 3-ditoyl tetrazolium chloride in the western Arctic Ocean (Yager et al. 2001, Huston & Deming 2002. These estimates are consistent with studies showing that a high fraction of bacteria (67 to 99%) and archaea (5 to 25%) are detected by fluorescence in situ hybridization (FISH) in Arctic water (Wells & Deming 2003, Garneau et al. 2006, Wells et al. 2006.Several bacterial groups are present in cold environments such as the Arctic Ocean. These groups include Bacteroidetes and several subdivisions of the Proteobacteria (Ferrari & Hollibaugh 1999, Bano & Hollibaugh 2002, Bowman et al. 2003. In surface waters of the Canadian Archipelago, the Cytophaga-Flavobacterium cluster makes up 9 to 41% of total cells (Wells & Deming 2003). In the shelf and shelf-break of the Beaufort Sea, Alphaproteobacteria dominate the bacterial community, followed by Gammaproteobacteria and Cytophaga-like bacteria (Garneau et al. 2006). These 3 phylogenetic groups are also the dominant bacterial groups in Arctic pack ice (Brinkmeyer et al. 2003). In other cold water environments, such as the North Sea and the Southern Ocean, Cytophaga-like bacteria are found to dominate the community, followed by Alphaprot...

Abundance and single‐cell activity of bacterial groups in Antarctic coastal waters

“…Cultureindependent studies suggest that although gammaproteobacterial abundance is often low in temperate waters, this group may be abundant in polar systems (Glö ckner et al 1999;Pommier et al 2007;Schattenhofer et al 2009). The Gammaproteobacteria are the third-most abundant group in the western Arctic, following the SphingobacteriaFlavobacteria (SF group) and Alphaproteobacteria (Elifantz et al 2007;Alonso-Saez et al 2008a). Antarctic bacterial communities have not been characterized as extensively as those in Arctic waters, and it is not clear if the two polar systems are dominated by the same broad taxa of bacteria.…”

“…Many of the broad taxa of bacteria found in lower latitudes are also present in the Arctic Ocean and in Antarctic waters as well (Bano and Hollibaugh 2002;Elifantz et al 2007;Murray and Grzymski 2007). Cultureindependent studies suggest that although gammaproteobacterial abundance is often low in temperate waters, this group may be abundant in polar systems (Glö ckner et al 1999;Pommier et al 2007;Schattenhofer et al 2009).…”

“…Early work suggested that bacterial growth is limited in cold temperatures, potentially requiring higher concentrations of substrate to achieve rates similar to bacterial growth in warmer, temperate waters (Pomeroy and Wiebe 2001). Yet single-cell studies have shown that in spite of low bulk rates, the fraction of individual cells that are active in the Arctic Ocean is high (Elifantz et al 2007;Malmstrom et al 2007;Vila-Costa et al 2008). Single-cell activity has been examined much less extensively in Antarctic waters.…”

“…SAR11 is the most abundant group in Arctic surface waters, comprising ,20% of the bacterial community, with 15-40% of the group actively incorporating leucine (Malmstrom et al 2007;Kirchman et al 2010). This fraction of active SAR11 cells is similar to what has been observed in temperate waters .…”

“…The alphaproteobacterial clade SAR11 is abundant in many marine environments and may play a role in polar systems as well (Malmstrom et al 2007;Schattenhofer et al 2009). SAR11 is the most abundant group in Arctic surface waters, comprising ,20% of the bacterial community, with 15-40% of the group actively incorporating leucine (Malmstrom et al 2007;Kirchman et al 2010).…”