Glacial meltwater influences on plankton community structure and the importance of top-down control (of primary production) in a NE Greenland fjord

Arendt, Kristine Engel; Agersted, Mette Dalgaard; Sejr, Mikael K.; Juul-Pedersen, Thomas

doi:10.1016/j.ecss.2016.08.026

Cited by 44 publications

(32 citation statements)

References 45 publications

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“…6) most likely reflect organic matter fluxes originating from the phytoplankton bloom that extends from outside the fjord and past the entrance sill (as seen by the fluorescence measurements, Figs. 3, 4), likely influenced by the vertical mixing across the shallow sill (Arendt et al 2016). Interestingly, the two lowest values measured in this zone are for YST1 and YST6, which both lie at a depth of about 60 m, where carbon oxidation is expected to exceed burial (Thamdrup et al 2007).…”

Section: Resultsmentioning

confidence: 99%

Sea ice and primary production proxies in surface sediments from a High Arctic Greenland fjord: Spatial distribution and implications for palaeoenvironmental studies

Ribeiro¹,

Sejr²,

Limoges³

et al. 2017

Ambio

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In order to establish a baseline for proxy-based reconstructions for the Young Sound–Tyrolerfjord system (Northeast Greenland), we analysed the spatial distribution of primary production and sea ice proxies in surface sediments from the fjord, against monitoring data from the Greenland Ecosystem Monitoring Programme. Clear spatial gradients in organic carbon and biogenic silica contents reflected marine influence, nutrient availability and river-induced turbidity, in good agreement with in situ measurements. The sea ice proxy IP25 was detected at all sites but at low concentrations, indicating that IP25 records from fjords need to be carefully considered and not directly compared to marine settings. The sea ice-associated biomarker HBI III revealed an open-water signature, with highest concentrations near the mid-July ice edge. This proxy evaluation is an important step towards reliable palaeoenvironmental reconstructions that will, ultimately, contribute to better predictions for this High Arctic ecosystem in a warming climate.

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Section: Resultsmentioning

confidence: 99%

Sea ice and primary production proxies in surface sediments from a High Arctic Greenland fjord: Spatial distribution and implications for palaeoenvironmental studies

Ribeiro¹,

Sejr²,

Limoges³

et al. 2017

Ambio

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“…Further, the silty glacial runoff drastically reduces the euphotic depth. The effects of the glacial runoff on the distribution of micro‐ and mesozooplankton (Arendt et al ; Middelbo et al ), marine ecosystem productivity (Meire et al ), colored DOM absorption (Murray et al ), and the carbon availability for bacteria (Paulsen et al ) have previously been described for Young Sound. Small phytoplankton (< 2 μ m) dominate the murky inner fjord and contribute on average 89% of chlorophyll a (Chl a ) compared to 59% at the mouth of the fjord.…”

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confidence: 99%

“…Small phytoplankton (< 2 μ m) dominate the murky inner fjord and contribute on average 89% of chlorophyll a (Chl a ) compared to 59% at the mouth of the fjord. At the same time, copepod grazing is considerably less in the inner fjord (Middelbo et al ), while protist grazing is enhanced (Arendt et al ). Copepods and protists generally dominate the grazer biomass in Young Sound, although the pelagic gastropod Limacina helicina is abundant particularly in autumn (Middelbo et al ).…”

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confidence: 99%

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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“…1, which was heavily influenced by fresh water, the direct grazing by copepods were only about 6% of the daily primary production during July and August (Figs. E, 7), and grazing by microzooplankton were likely more important (Arendt et al ). At the stations less influenced by fresh water the grazing impact by copepods was substantially higher (Figs.…”

Section: Discussionmentioning

confidence: 99%

Impact of glacial meltwater on spatiotemporal distribution of copepods and their grazing impact in Young Sound NE, Greenland

Middelbo

Sejr

Arendt

et al. 2017

Limnology & Oceanography

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The melting of sea ice, increased terrestrial runoff and meltwater from the Greenland Ice Sheet contribute to increased freshening and stratification of Arctic seas. However, the impacts on ecosystem structure and carbon cycling are still poorly quantified. We studied copepod abundance, grazing, and carbon turnover in Young Sound, Northeast Greenland, during the ice-free period from mid-July to early October 2014 at four stations along the freshwater gradient from the inner fjord to the Greenland Sea. Freshwater enters the fjord as surface runoff from land-terminating glaciers and forms a surface layer of high turbidity and low salinity limiting light availability and nutrient replenishment. This resulted in the inner station consistently having lower biomass of chlorophyll a, (average 21 mg m 22) compared to the outer station (47 mg m 22) and phytoplankton cells smaller than 10 lm constituted 89% at the inner station compared to 59% at the outer station. Copepod grazing rates were low on these small cells, which resulted in low copepods community grazing at the freshwater impacted site in the inner fjord. Daily grazing impact by copepods was about half of the daily primary production during July and August in the outer region of the fjord, but grazing impact was always less than 10% of the daily primary production in the inner fjord and in the late part of the open water season at all stations. Our study shows that meltwater driven stratification results in dominance of small phytoplankton cells, which directly impacts secondary producers and reduces transfer to higher trophic levels.

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Glacial meltwater influences on plankton community structure and the importance of top-down control (of primary production) in a NE Greenland fjord

Cited by 44 publications

References 45 publications

Sea ice and primary production proxies in surface sediments from a High Arctic Greenland fjord: Spatial distribution and implications for palaeoenvironmental studies

Sea ice and primary production proxies in surface sediments from a High Arctic Greenland fjord: Spatial distribution and implications for palaeoenvironmental studies

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

Impact of glacial meltwater on spatiotemporal distribution of copepods and their grazing impact in Young Sound NE, Greenland

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