Spatial distribution of benthic foraminiferal stable isotopes and dinocyst assemblages in surface sediments of the Trondheimsfjord, central Norway

Milzer, G.; Giraudeau, Jacques; Faust, Johan C.; Knies, Jochen; Eynaud, Frédérique; Rühlemann, Carsten

doi:10.5194/bg-10-4433-2013

Cited by 19 publications

(24 citation statements)

References 72 publications

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“…Within the main groups of organic‐walled microfossils, R. corbiferum dominates over dinocysts, which are almost absent. The biological affinity of R. corbiferum is currently unknown, but this acritarch is commonly reported from brackish environments or inner‐shelf settings with low surface salinities (Kunz‐Pirrung, ; Matthiessen et al, ; Milzer et al, ; Sorrel et al, ). The assemblages likely indicate lower salinities in this area.…”

Section: Discussionmentioning

confidence: 99%

Linking the Modern Distribution of Biogenic Proxies in High Arctic Greenland Shelf Sediments to Sea Ice, Primary Production, and Arctic‐Atlantic Inflow

et al. 2018

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The eastern north coast of Greenland is considered to be highly sensitive to the ongoing Arctic warming, but there is a general lack of data on modern conditions and in particular on the modern distribution of climate and environmental proxies to provide a baseline and context for studies on past variability. Here we present a detailed investigation of 11 biogenic proxies preserved in surface sediments from the remote High Arctic Wandel Sea shelf, the entrance to the Independence, Hagen, and Danmark fjords. The composition of organic matter (organic carbon, C:N ratios, δ13C, δ15N, biogenic silica, and IP25) and microfossil assemblages revealed an overall low primary production dominated by benthic diatoms, especially at the shallow sites. While the benthic and planktic foraminiferal assemblages underline the intrusion of chilled Atlantic waters into the deeper parts of the study area, the distribution of organic‐walled dinoflagellate cysts is controlled by the local bathymetry and sea ice conditions. The distribution of the dinoflagellate cyst Polarella glacialis matches that of seasonal sea ice and the specific biomarker IP25, highlighting the potential of this species for paleo sea ice studies. The information inferred from our multiproxy study has important implications for the interpretation of the biogenic‐proxy signal preserved in sediments from circum‐Arctic fjords and shelf regions and can serve as a baseline for future studies. This is the first study of its kind in this area.

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Section: Discussionmentioning

confidence: 99%

Linking the Modern Distribution of Biogenic Proxies in High Arctic Greenland Shelf Sediments to Sea Ice, Primary Production, and Arctic‐Atlantic Inflow

et al. 2018

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“…Brückner and Mackensen, 2008;Milzer et al, 2013). To decipher these effects is difficult in studies such as the one presented.…”

Section: Stable Isotopes Vital Effects and Carbon Accumulation Ratesmentioning

confidence: 99%

Spatial and temporal organic carbon burial along a fjord to coast transect: A case study from Western Norway

et al. 2017

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We investigated spatial and temporal changes in accumulation rate and source of organic carbon on a gradient along the Lysefjord and the more coastal Høgsfjord, Western Norway. This was achieved through analysis of total organic carbon and nitrogen content of sediment cores, which were radiometrically dated to the early 19th and 20th centuries for the Høgsfjord and Lysefjord, respectively. Benthic foraminifera (protists) were utilized to determine changes in organic carbon supply and Ecological Quality Status (EcoQS) by their accumulation rate (benthic foraminiferal accumulation rate (BFAR)), assemblage composition, species diversity, individual species responses and the composition of stable carbon isotopes of the tests (shells) of Cassidulina laevigata, Hyalinea balthica and Melonis barleeanus. Organic carbon accumulation rates were greatest closest to the river Lyse at the head of the Lysefjord (83-171 g C m −2 yr −1 ). The organic carbon at the head of the fjord is mainly terrestrial in origin, and this terrestrial influence becomes progressively less seaward. The δ 13 C in H. balthica tests as well as the benthic foraminiferal assemblage composition also showed a clear fjord to coast gradient. Organic carbon accumulation rates were lower and less variable at the seaward study sites (13-61 g C m −2 yr −1 ). We observe no temporal trend in organic carbon, carbon isotopes, EcoQS or foraminiferal assemblage composition in the Lysefjord. In contrast, in the Høgsfjord, there seems to have been an increase in organic carbon accumulation rates during the 1940s. Subsequent accumulation rates are stable. The foraminiferal assemblages in the surface sediments reflect a recent transition from good/moderate to moderate/bad EcoQS.

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“…These hydrological changes may however be biased by local and regional anthropogenically induced changes in the coastal and fjord environment (Saetre et al, 1997;Dale, 2001). Recent studies on surface sediments from the Trondheimsfjord which encompass the past 4-20 yr, show large spatial variability in the composition of cyst assemblages linked to the complex fjord hydrography and topography (Milzer et al, 2013). Untreated waste water from local and regional industry and agriculture was directly led into the Trondheimsfjord until 1980.…”

Section: Introductionmentioning

confidence: 99%

“…1) (Ellingsen, 2004, and references therein). Sediment deposition in the Trondheimsfjord is largely controlled by the prevalent currents and the associated pelagic/marine sediment load, the topography and rivers delivering large amounts of terrigenous sediment to the fjord (Bøe et al, 2003;Milzer et al, 2013). Bottom currents and tidal currents in the subsurface layers prevent the rapid deposition of the fine particle fraction in topographically elevated areas as sills, and trigger the sediment remobilisation across the fjord.…”

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confidence: 99%

“…Bottom currents and tidal currents in the subsurface layers prevent the rapid deposition of the fine particle fraction in topographically elevated areas as sills, and trigger the sediment remobilisation across the fjord. Sedimentation rates are consequently higher in the sheltered fjord basins such as Middle Fjord and Beitstadfjord than at the fjord entrance and in the Seaward Basin where several currents pass at high frequencies (Bøe et al, 2003;Milzer et al, 2013).…”

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confidence: 99%

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Qualitative and quantitative reconstruction of surface water characteristics and recent hydrographic changes in the Trondheimsfjord, central Norway

Milzer¹,

Giraudeau²,

Schmidt³

et al. 2013

Preprint

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In the present study we investigate dinocyst assemblages in the Trondheimsfjord over the last 25 to 50 yr from three well-dated multi-cores (²¹⁰Pb and ¹³⁷Cs) retrieved along the fjord axis. The downcore distribution of the cysts is discussed in view of changes of the key surface water parameters sea-surface temperatures (SSTs) and sea-surface salinities (SSSs) monitored in the fjord, as well as river discharges. We examine the impact of the North Atlantic Oscillation pattern and of waste water supply from the local industry and agriculture on the fjord ecological state and hence dinocyst species diversity. Our results show that dinocyst production and diversity in the fjord is not evidently affected by human-induced eutrophication. Instead the assemblages appear to be mainly controlled by the NAO-related changes in physico-chemical characteristics of the surface mixed layer. Still, discharges of major rivers were modulated, since 1985 by the implementation of hydropower plants which certainly influences the freshwater and nutrient supply into the fjord. The impact, however, is variable according to the local geographical setting, and barely differentiated from natural changes in river run off.

We ultimately test the use of the modern analogue technique (MAT) for the reconstruction of winter and summer SSTs and SSSs and annual primary productivity (PP) in this particular fjord setting. The reconstructed data are compared with time-series of SSTs and SSSs measured at 10 m water depth, as well as with mean annual PPs along the Norwegian coast and within Scandinavian fjords. The reconstructions are in general good agreement with the instrumental measurements and observations from other fjords. Major deviations can be addressed to peculiarities in the assemblages linked to the particular fjord setting and the related hydrological structure

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Spatial distribution of benthic foraminiferal stable isotopes and dinocyst assemblages in surface sediments of the Trondheimsfjord, central Norway

Cited by 19 publications

References 72 publications

Linking the Modern Distribution of Biogenic Proxies in High Arctic Greenland Shelf Sediments to Sea Ice, Primary Production, and Arctic‐Atlantic Inflow

Linking the Modern Distribution of Biogenic Proxies in High Arctic Greenland Shelf Sediments to Sea Ice, Primary Production, and Arctic‐Atlantic Inflow

Spatial and temporal organic carbon burial along a fjord to coast transect: A case study from Western Norway

Qualitative and quantitative reconstruction of surface water characteristics and recent hydrographic changes in the Trondheimsfjord, central Norway

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