scholarly journals Stable Silicon Isotopes Uncover a Mineralogical Control on the Benthic Silicon Cycle in the Arctic Barents Sea

2021 ◽  
Author(s):  
James Ward ◽  
Katharine Hendry ◽  
Sandra Arndt ◽  
Johan Faust ◽  
Felipe Freitas ◽  
...  
Keyword(s):  
Pore Water ◽  
Phytoplankton Community ◽  
Barents Sea ◽  
Solid Phase ◽  
The Arctic ◽  
Lower Latitude ◽  
Sediment Pore Water ◽  
Mass Balance Calculation ◽  
Silicon Isotopes ◽  
Phytoplankton Communities

Biogeochemical cycling of silicon (Si) in the Barents Sea is under considerable pressure from physical and chemical changes, including dramatic warming and sea ice retreat, together with a decline in dissolved silicic acid (DSi) concentrations of Atlantic inflow waters since 1990. Moreover, further expansion of the Atlantic realm (termed `Atlantification') is expected to shift phytoplankton community compositions away from diatom-dominated spring bloomsin favour of Atlantic flagellate species (coccolithophore-dominated). The changes in pelagic primary production will alter the composition of the material comprising the depositional flux, which will subsequently in influence the recycling processes at and within the seafloor. In this study we assess the predominant controls on the early diagenetic cycling of Si, a key nutrient in marine ecosystems, by combining stable isotopic analysis of pore water DSi and of operationally defined reactive pools of the solid phase. We show that low biogenic silica (BSi) contents (0.39-0.52 wt% or 92-185 μmol g dry wt-1) drive correspondingly low asymptotic concentrations of pore water DSi (~100 μM). However, while these surface sediments appear almost devoid of BSi, we present evidence for the rapid recycling of bloom derived BSi that generates striking transient peaks in sediment pore water [DSi], which is a feature that is subject to future shifts in phytoplankton community compositions. Using a simple mass balance calculation we show that the pore water DSi pool is supplemented by a lithogenic Si source (LSi), while our sediment pore water Si isotopic profiles also uncover a coupling of the iron (Fe) and Si cycles. This has previously been observed in lower latitude marine sediment systems and thus provides further support for a redox influence on oceanic pore water DSi. We suggest that a high LSi:BSi ratio and apparent Fe (oxyhydr)oxide influence could lead to a degree of stability in the annual background benthic flux of DSi despite the pressures on pelagic phytoplankton communities. Coupled with supporting isotopic evidence for the precipitation of authigenic clays in Barents Sea sediment cores, our observations have implications for the sink vs recycling terms in the regional Si budget.

scholarly journals Spectral Characterization of Dissolved Organic Matter in Seawater and Sediment Pore Water from the Arctic Fjords (West Svalbard) in Summer

Water ◽  
2021 ◽  
Vol 13 (2) ◽  
pp. 202
Author(s):  
Meilian Chen ◽  
Ji-Hoon Kim ◽  
Sungwook Hong ◽  
Yun Kyung Lee ◽  
Moo Hee Kang ◽  
...  
Keyword(s):  
Organic Matter ◽  
Dissolved Organic Matter ◽  
Pore Water ◽  
Phytoplankton Bloom ◽  
Ocean Surface ◽  
The Arctic ◽  
Sediment Pore Water ◽  
Ice Edge ◽  
Accumulation Trend ◽  
Arctic Fjords

Fjords in the high Arctic, as aquatic critical zones at the interface of land-ocean continuum, are undergoing rapid changes due to glacier retreat and climate warming. Yet, little is known about the biogeochemical processes in the Arctic fjords. We measured the nutrients and the optical properties of dissolved organic matter (DOM) in both seawater and sediment pore water, along with the remote sensing data of the ocean surface, from three West Svalbard fjords. A cross-fjord comparison of fluorescence fingerprints together with downcore trends of salinity, Cl−, and PO43− revealed higher impact of terrestrial inputs (fluorescence index: ~1.2–1.5 in seawaters) and glaciofluvial runoffs (salinity: ~31.4 ± 2.4 psu in pore waters) to the southern fjord of Hornsund as compared to the northern fjords of Isfjorden and Van Mijenfjorden, tallying with heavier annual runoff to the southern fjord of Hornsund. Extremely high levels of protein-like fluorescence (up to ~4.5 RU) were observed at the partially sea ice-covered fjords in summer, in line with near-ubiquity ice-edge blooms observed in the Arctic. The results reflect an ongoing or post-phytoplankton bloom, which is also supported by the higher levels of chlorophyll a fluorescence at the ocean surface, the very high apparent oxygen utilization through the water column, and the nutrient drawdown at the ocean surface. Meanwhile, a characteristic elongated fluorescence fingerprint was observed in the fjords, presumably produced by ice-edge blooms in the Arctic ecosystems. Furthermore, alkalinity and the humic-like peaks showed a general downcore accumulation trend, which implies the production of humic-like DOM via a biological pathway also in the glaciomarine sediments from the Arctic fjords.

MEASURING PYRETHROIDS IN SEDIMENT PORE WATER USING MATRIX-SOLID PHASE MICROEXTRACTION

2009 ◽  
Vol 28 (1) ◽  
pp. 36 ◽  
Author(s):  
Wesley Hunter ◽  
Yu Yang ◽  
Fredrik Reichenberg ◽  
Philipp Mayer ◽  
Jianying Gan
Keyword(s):  
Pore Water ◽  
Solid Phase Microextraction ◽  
Solid Phase ◽  
Sediment Pore Water

scholarly journals Phytoplankton community structure in the Lena Delta (Siberia, Russia) in relation to hydrography

2013 ◽  
Vol 10 (2) ◽  
pp. 2305-2344 ◽  
Author(s):  
A. C. Kraberg ◽  
E. Druzhkova ◽  
B. Heim ◽  
M. J. G. Loeder ◽  
K. H. Wiltshire
Keyword(s):  
Climate Change ◽  
Phytoplankton Community ◽  
The Arctic ◽  
Permafrost Region ◽  
Laptev Sea ◽  
Freshwater Species ◽  
River Channels ◽  
Direction Parallel ◽  
Phytoplankton Communities ◽  
Lena Delta

Abstract. The Lena Delta in Northern Siberia is one of the largest river deltas in the world. During peak discharge, after the ice melt in spring, it delivers between 60–8000 m3s−1 of water and sediment into the Arctic Ocean. The Lena Delta and the Laptev Sea coast also constitute a~continuous permafrost region. Ongoing climate change, which is particularly pronounced in the Arctic, is leading to increased rates of permafrost thaw. This is likely to profoundly change the discharge rates of the Lena River and the chemistry of the river waters which are discharged into the coastal Laptev Sea, e.g. by increasing concentrations of inorganic nutrients, DOC and importantly methane. These physical and chemical changes will also affect the composition of and interactions between phytoplankton and zooplankton communities, forming the basis of the food web. However, before potential consequences of climate change for coastal arctic plankton communities can be judged, the inherent status of the diversity and linked foodweb interactions within the delta need to be established. As part of the AWI Lena Delta Programme in 2010 the phyto- and microzooplankton community in three river channels as well as four coastal transects were investigated to capture the typical river phytoplankton communities and the transitional zone of brackish/marine conditions. Most CTD profiles from 23 coastal stations showed very strong stratification. The only exception to this was a small a shallow and mixed area running from the outflow of Bykovskaya channel in a northerly direction parallel to the shore (transect 3). Of the five stations in this area three had a salinity of close to zero. Two further stations had salinities of around 2 and 5 throughout the water column. In the remaining transects on the other hand salinities varied between 5–30 with depth. Phytoplankton counts from the outflow from the Lena were dominated by diatoms (Aulacoseira species) cyanobacteria (Aphanizomenon, Pseudanabaena) and chlorophytes, in those stations characterized by river outflow (stations in the Lena itself and in coastal transect 3). In contrast in the stratified stations the plankton was mostly dominated by dinoflagellates, ciliates and nanoflagellates, with only an insignificant diatom component from the genera Chaetoceros and Thalassiosira (brackish as opposed to freshwater species). Ciliate abundance was significantly coupled with the abundance of total flagellates. A pronounced partitioning in the phytoplankton community was also discernible with depth, with a different community composition and abundance above and below the thermocline in the stratified sites. This work represents the first attempt at analyzing the phytoplankton structure of the region of freshwater influence at confluence Lena–Laptev sea.

scholarly journals Phytoplankton community structure in the Lena Delta (Siberia, Russia) in relation to hydrography

2013 ◽  
Vol 10 (11) ◽  
pp. 7263-7277 ◽  
Author(s):  
A. C. Kraberg ◽  
E. Druzhkova ◽  
B. Heim ◽  
M. J. G. Loeder ◽  
K. H. Wiltshire
Keyword(s):  
Climate Change ◽  
Community Structure ◽  
Phytoplankton Community ◽  
The Arctic ◽  
Laptev Sea ◽  
Phytoplankton Community Structure ◽  
Lena River ◽  
Phytoplankton Communities ◽  
The Laptev Sea ◽  
Lena Delta

Abstract. The Lena Delta in Northern Siberia is one of the largest river deltas in the world. During peak discharge, after the ice melt in spring, it delivers between 60–8000 m3 s−1 of water and sediment into the Arctic Ocean. The Lena Delta and the Laptev Sea coast also constitute a continuous permafrost region. Ongoing climate change, which is particularly pronounced in the Arctic, is leading to increased rates of permafrost thaw. This has already profoundly altered the discharge rates of the Lena River. But the chemistry of the river waters which are discharged into the coastal Laptev Sea have also been hypothesized to undergo considerable compositional changes, e.g. by increasing concentrations of inorganic nutrients such as dissolved organic carbon (DOC) and methane. These physical and chemical changes will also affect the composition of the phytoplankton communities. However, before potential consequences of climate change for coastal arctic phytoplankton communities can be judged, the inherent status of the diversity and food web interactions within the delta have to be established. In 2010, as part of the AWI Lena Delta programme, the phyto- and microzooplankton community in three river channels of the delta (Trofimov, Bykov and Olenek) as well as four coastal transects were investigated to capture the typical river phytoplankton communities and the transitional zone of brackish/marine conditions. Most CTD profiles from 23 coastal stations showed very strong stratification. The only exception to this was a small, shallow and mixed area running from the outflow of Bykov channel in a northerly direction parallel to the shore. Of the five stations in this area, three had a salinity of close to zero. Two further stations had salinities of around 2 and 5 throughout the water column. In the remaining transects, on the other hand, salinities varied between 5 and 30 with depth. Phytoplankton counts from the outflow from the Lena were dominated by diatoms (Aulacoseira species) cyanobacteria (Aphanizomenon, Pseudanabaena) and chlorophytes. In contrast, in the stratified stations the plankton was mostly dominated by dinoflagellates, ciliates and nanoflagellates, with only an insignificant diatom component from the genera Chaetoceros and Thalassiosira (brackish as opposed to freshwater species). Ciliate abundance was significantly coupled with the abundance of total flagellates. A pronounced partitioning in the phytoplankton community was also discernible with depth, with a different community composition and abundance above and below the thermocline in the stratified sites. This work is a first analysis of the phytoplankton community structure in the region where Lena River discharge enters the Laptev Sea.

ANALYSIS OF PYRETHROIDS IN SEDIMENT PORE WATER BY SOLID-PHASE MICROEXTRACTION

2007 ◽  
Vol 26 (12) ◽  
pp. 2587 ◽  
Author(s):  
Svetlana Bondarenko ◽  
Frank Spurlock ◽  
Jianying Gan
Keyword(s):  
Pore Water ◽  
Solid Phase Microextraction ◽  
Solid Phase ◽  
Sediment Pore Water
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