Upstream Freshwater and Terrestrial Sources Are Differentially Reflected in the Bacterial Community Structure along a Small Arctic River and Its Estuary

Hauptmann, Aviaja Zenia Edna Lyberth; Markussen, Thor Nygaard; Stibal, Marek; Olsen, Nikoline S.; Elberling, Bo; Bælum, Jacob; Sicheritz-Pontén, Thomas; Jacobsen, Carsten Suhr

doi:10.3389/fmicb.2016.01474

Cited by 46 publications

(43 citation statements)

References 47 publications

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“…The bacterial communities in the rivers were highly specific to each of them (Figure 8), which we suggest is due to their difference in origin and catchment area; close connection (0.5 km) to the Greenland Ice Sheet (R1), longer distance (2 km) from smaller local glacier (R2), and the lowland vegetation rich river with lake connection (R3). This is in agreement with a recent study from West Greenland that similarly show distinct communities in rivers and a proglacial lake over a 2 km distance (Hauptmann et al, 2016), and find less terrestrial species in river samples with a more direct connection to glaciers.…”

Section: Bacterial Community Compositionsupporting

confidence: 93%

Heterotrophic nanoflagellate grazing facilitates subarctic Atlantic spring bloom development

Paulsen¹,

Riisgaard²,

John³

et al. 2017

Aquat. Microb. Ecol.

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My study underpins that picophytoplankton are important contributors to primary production, especially during the winter-spring transition (Paper I and III) and autumn (Paper V). They boosted the growth of heterotrophic microorganisms before the onset of the diatom spring bloom in the Subarctic Atlantic (Paper I) and dominated the phytoplankton biomass in the high turbid parts of a NE Greenland fjord influenced by glacial meltwater (Paper V). Picophytoplankton were better adapted to low light conditions and demonstrated higher growth rates, than larger phytoplankton (Paper I, II, III, V). In the Polar-influenced water near Greenland, Synechococcus were negligible, while in the Atlantic influenced waters picoeukaryotes and Synechococcus were often equally abundant and the latter dominated on several occasions during autumn and winter (Paper I and III). Unexpectedly, abundances of Synechococcus were as high at 65°N as at 79°N, and molecular analysis suggests the presence of new clades specially adapted to Arctic conditions. Bacteria were generally rather carbon-than nutrient limited, and their abundance increased rapidly in response to the pre-bloom picophytoplankton production of labile carbon in both the Arctic and Subarctic (Paper I and V). In NE Greenland the terrestrial DOM supplied from the Greenland ice sheet proved to be highly bioavailable compared to the 7 autochthonous fjord DOM (Paper IV). The in situ changes in DOM, which were examined via fluorescence signal of different DOM components (FDOM), surprisingly demonstrated that the highest net-growth of bacteria was not coupled to the labile glacial runoff in the surface, but rather to sub-surface the humic-DOM, commonly considered to be refractory. This may be explained by the presence of specific dominating taxa of bacteria that had the ability to degrade humic-DOM (Paper V).Across regions, HNF exerted strong control of picophytoplankton and bacteria (Paper I, II, III, V). HNF grew significantly faster than microzooplankton and were therefore less affected by mixing and relatively more important grazers than their micro-sized counterparts in well-mixed water columns (Paper I and II). HNF larger than 5µm controlled picophytoplankton particularly in the early productive season, while small HNF (3-5µm) mainly kept bacteria in check in autumn (Paper III, V). In conclusion, the studies underline that pico-sized plankton play a fundamental part in the carbon transfer in high latitude ecosystems both as primary producers and via the microbial loop. Picophytoplankton appeared better adapted than larger phytoplankton to low light conditions, and bacteria were capable of degrading terrestrial derived DOM, however, these abilities are highly community specific. The data suggest that a change in mixing patters will affect the microbial food structure and that shifts in coastal microbial community composition should be anticipated with increased runoff. 8 List of publicationsThe thesis is based on preliminary data and the following fived papers referred to in the t...

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Section: Bacterial Community Compositionsupporting

confidence: 93%

Heterotrophic nanoflagellate grazing facilitates subarctic Atlantic spring bloom development

Paulsen¹,

Riisgaard²,

John³

et al. 2017

Aquat. Microb. Ecol.

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“…The FDOM signals from the three rivers were directly related to their catchment, with the glacial rivers R1 and R2 supplying similar and low signal, while the tundra and lakes in the R3 catchment supply an elevated and more variable signal. Similar variations in FDOM intensity of large Arctic rivers have been explained by the difference in the vegetation characteristics of the catchment (Walker et al ), further the presence of proglacial lakes results in higher DOC concentrations (340–406 μ M C) (Bhatia et al ; Hauptmann et al ). The low‐carbon content in glacial meltwater in Young Sound is consistent previous observations from the western part of Greenland Ice Sheet with 7–32 μ M C, 15–51 μ M C, and 21–100 μ M C found in subglacial, supraglacial discharge, and a glacial stream with connection to a proglacial lake, respectively (Bhatia et al ; Lawson et al ; Hauptmann et al ).…”

Section: Discussionmentioning

confidence: 59%

Biological transformation of Arctic dissolved organic matter in a NE Greenland fjord

Paulsen

Müller

Larsen

et al. 2018

Limnology & Oceanography

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Arctic waters are often enriched with terrestrial dissolved organic matter (DOM) characterized by having elevated visible wavelength fluorescence (commonly termed humic-like). Here, we have identified the sources of fluorescent DOM (FDOM) in a high Arctic fjord (Young Sound, NE Greenland) influenced by glacial meltwater. The biological transformation of FDOM was further investigated using plankton community size-fractionation experiments. The intensity of ultraviolet fluorescence (commonly termed amino acid-like) was highly variable and positively correlated to bacterial production and mesozooplankton grazing. The overall distribution of visible FDOM in the fjord was hydrographically driven by the high-signal intrusion of Arctic terrestrial DOM from shelf waters and dilution with glacial runoff in the surface waters. However, the high-intensity visible FDOM that accumulated in subsurface waters in summer was not solely linked to allochthonous sources. Our data indicate that microbial activity, in particular, protist bacterivory, to be a source. A decrease in visible FDOM in subsurface waters was concurrent with an increase in bacterial abundance, indicating an active bacterial uptake or modification of this DOM fraction. This was confirmed by net-loss of visible FDOM in experiments during summer when bacterial activity was high. The degradation of visible FDOM appeared to be associated with bacteria belonging to the order Alteromonadales mainly the genus Glaciecola and the SAR92 clade. The findings provide new insight into the character of Arctic terrestrial DOM and the biological production and degradation of both visible and UV wavelength organic matter in the coastal Arctic.

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“…It has been previously reported that the microbial community in both surface and subsurface soils from Tibet are influenced by total carbon and the carbon to nitrogen ratio . The total bacterial community structure in a small Arctic river was significantly correlated with turbidity, but the estuary bacterial community was not significantly correlated with any environmental factor . Thus bacterial communities in different ecosystems are influenced by different environmental variables.…”

Section: Discussionmentioning

confidence: 88%

“…A previous study suggested that sediments have a higher bacterial diversity than any other type of environment at a global scale . The diversity and community composition of bacteria in river sediments are distinct from those in estuary sediments . Abundance and activity of bacteria in the marine and brackish water zones are distinct due to different freshwater regimes .…”

Section: Introductionmentioning

confidence: 95%

“…In addition, a high variability in pH value, salinity, and concentrations of nutrients, which are main controlling factors of bacterial community structure, would be exhibited among different habitats. Previous studies mainly focused on either river to marine environments or intertidal wetland . Comparison of the bacterial diversity in sediments from freshwater, intertidal wetland, and marine was revealed for the first time in the Pearl River in south China , but the correlation between bacterial community structure and environmental factors is unavailable.…”

Section: Introductionmentioning

confidence: 99%

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Spatial variation in bacterial community in natural wetland‐river‐sea ecosystems

et al. 2017

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Wetland-estuarine-marine environments are typical oxic/anoxic transition zones and have complex water flow-paths within the zone of mixing where freshwater interacts with ocean water. Little is known about the impact of this interaction on bacterial community structures or the relationship between bacterial community and geochemical factors in such transitional mixing environments. Hence, we investigated the distribution patterns and diversity in bacterial communities in the Yellow River estuary-coastal wetland-Bohai Sea transition zone by analyzing 39 samples from 13 ordered sites. High-throughput sequencing of the 16S rRNA gene revealed significant shifts in diversity and distribution of bacterial community in sediments from the Yellow River estuary to the Bohai Sea. Yellow River sediment was dominated by hydrogen-, nitrogen-, and iron-cycling bacteria, such as Hydrogenophaga, Nitrospira, Pseudomonas, and Thiobacillus. The coastal wetland had a haloduric community associated with different functions, such as Planctomyces, Marinobacter, Halomonas, Salinivibrio, and Salinibacter. The Bohai Sea sediment had a higher relative abundance of Lutimonas, Desulfococcus, Photobacterium, Propionigenium, and Vibrio. Spatial variation in bacterial community was correlated with pH, salinity and sulfate (SO42-) concentration in such coastal environments. The major bacterial taxa were significantly different across the wetland, estuary, and coastal marine ecosystems, indicating substantial spatial heterogeneity among the three ecosystems. Statistical analysis revealed strong links between variation in bacterial community structure and ecosystem type. Our results demonstrate the importance of geographic and geochemical factors in structuring the bacterial community in natural environments.

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Upstream Freshwater and Terrestrial Sources Are Differentially Reflected in the Bacterial Community Structure along a Small Arctic River and Its Estuary

Cited by 46 publications

References 47 publications

Heterotrophic nanoflagellate grazing facilitates subarctic Atlantic spring bloom development

Heterotrophic nanoflagellate grazing facilitates subarctic Atlantic spring bloom development

Biological transformation of Arctic dissolved organic matter in a NE Greenland fjord

Spatial variation in bacterial community in natural wetland‐river‐sea ecosystems

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