Fine Sediment in Open Water

10.1142/12473 ◽  
2022 ◽  
Author(s):  
Johan C Winterwerp ◽  
Thijs van Kessel ◽  
Dirk S van Maren ◽  
Bram C van Prooijen
Keyword(s):  
2019 ◽  
Vol 31 (2) ◽  
pp. 80-88 ◽  
Author(s):  
Stacy Kim

AbstractHabitats under ice shelves are minimally explored, primarily because of technological limitations. These areas are separated from photosynthetic primary productivity by thick ice and distance to open water. Nevertheless, a diverse macrofaunal benthic community was discovered at 188 m depth, 80 km back from the edge of the McMurdo Ice Shelf. The general habitat was fine sediment with occasional dropstones, and dominant taxa were polychaetes and brittle stars, with alcyonacean soft corals and anemones on hard substrates. Gelatinous animals were abundant near the seafloor, and possibly part of a food web that supports the benthic community.


2021 ◽  
Author(s):  
David Piatka ◽  
Romy Wild ◽  
Jürgen Geist ◽  
Robin Kaule ◽  
Ben Gilfedder ◽  
...  

<p>Dissolved oxygen (DO) in the hyporheic zone (HZ) is a crucial parameter for the survival of many stream organisms and is involved in a multitude of aerobic chemical reactions. However, HZ DO budgets are easily perturbed by climate change and anthropogenic processes that have caused increased deposition of fine sediments (< 2 mm) in many stream beds. The fine sediment fraction hampers exchange of DO-rich stream water with the HZ. In this study we performed a raster sampling approach (0.90 cm length x 1.50 cm width; 30 cm distance between sampling points) at sediment depths of 10 and 25 cm with a focus on DO and its stable isotopes (δ<sup>18</sup>O<sub>DO</sub>). The aim was to analyze small-scale turnover patterns in a forested (site 1) and an anthropogenically influenced stream section (site 2) in a 3<sup>rd</sup> order stream in southern Germany. Grain size analyses showed similar average fine sediment fractions at site 1 (42.5 ±13.7 %) and site 2 (46.3 ±10.8 %). They increased with depth at both sites (38.5 ± 6.3 %, 0-15 cm; 46.5 ± 17.4 %, 15-30 cm at site 1 and 40.6 ±4.5 %, 0-15 cm; 52.0 ±12.2 %, 15-30 cm at site 2). DO concentrations in the HZ ranged from 1.4 to 4.5 mg L<sup>-1</sup> (2.0 ±0.7 mg L<sup>-1</sup>) and 1.5 to 1.8 mg L<sup>-1</sup> (1.7 ±0.1 mg L<sup>-1</sup>) at site 1 and from 1.2 to 2.9 mg L<sup>-1</sup> (1.6 ±0.5) and 1.0 to 2.4 mg L<sup>-1</sup> (1.6 ±0.4) at site 2 at 10 and 25 cm depth, respectively. The low DO concentrations in the HZ suggest high DO consumption rates and reduced exchange with stream water. This is possibly a result of increased fine sediment proportions. However, other factors such as organic carbon contents and increased respiration rates may also influence DO gradients. In contrast, the stream water had an average DO concentration of 9.8 ±0.2 mg L<sup>-1</sup>. Associated δ<sup>18</sup>O<sub>DO</sub> values of the open water (23.4 ±0.1 ‰) differed from those of sediment waters that showed averages of +22.5 ±0.5 ‰ and +22.4 ±0.3 ‰ at site 1 and +22.5 ±0.4 ‰ and +22.3 ±0.2 ‰ at site 2 at 10 and 25 cm depth, respectively. These sedimentary values indicated dominant photosynthesis, even though due to absence of light in the subsurface this process seems unlikely. Therefore, kinetically-driven processes such as diffusion, interactions with Fe or unknown DO sources within the HZ might have caused such <sup>16</sup>O-enriched values. Our findings suggest that the analyses of DO, δ<sup>18</sup>O<sub>DO</sub> and fine sediment gradients in the HZ should be combined with stable carbon isotope measurements to further our understanding of hyporheic processes relevant for stream biota.</p><p> </p>


2006 ◽  
Vol 32 (2) ◽  
pp. 196-201 ◽  
Author(s):  
Janet M. Lanyon ◽  
Rob W. Slade ◽  
Helen L. Sneath ◽  
Damien Broderick ◽  
John M. Kirkwood ◽  
...  
Keyword(s):  

Author(s):  
Olga Mashtaler ◽  
Olga Mashtaler ◽  
Alexander Myasoedov ◽  
Alexander Myasoedov ◽  
Elizaveta Zabolotskikh ◽  
...  

The relevance of the polar lows (PLs) research is justified by their great destructive power and creation of threat to the safety of navigation in the high latitudes and along the Northern Sea Route. The most dangerous effects on maritime activities are strong winds, waves and icing. In addition, the study of the PLs acquires relevance due to the sharp decrease of the sea ice area in the Arctic in recent years and the emergence of areas of open water, suitable for the appearance and development of PLs. However, despite the importance of PLs, they are apparently not sufficiently studied. As there are no meteorological observations in the areas of their appearance, the main source of information about them are satellite observations. By using images on the SOLab SIOWS Arctic Portal from multiple satellites operating in the IR and visible ranges (e.g., MODIS and AVHRR), and using near-water wind fields from high resolution synthetic aperture radars (Sentine-1, ASAR) and low resolution scatterometers (ASCAT), we identify polar lows in various parts of the Arctic, revealing statistical regularities in the appearance of PLs, their distribution and intensity. Collected database of Pls and their characteristics will be used for further PLs forecasting model development.


Author(s):  
Dipayan Dey ◽  
Dipayan Dey ◽  
Ashoka Maity ◽  
Ashoka Maity

Algae has a great potential for quick capture of biological carbon and its storage in saltwater-inundated coastal wetlands and can also be introduced as a climate adaptive alternate farming practice. An intervention with native algal flora Enteromorpha sp. in enclosed coastal Sundarbans in India on two open water culture techniques, viz. U-Lock & Fish-Bone, shows that growth in native algal stock is influenced by seasonal variations of salinity and other limnological factors. Sundarbans, facing the odds of climate change is fast loosing arable lands to sea level rise. Algaculture in inundated coastal areas can be an adaptive mitigation for the same. Perusal of results show that daily growth rate (DGR%) increases with increasing salinity of the intruding tidal waters to an extent and biomass increment under salt stress results in accumulation of metabolites those are having nutrient values and can yield bio-diesel as well. Algal growth recorded mostly in post monsoon period, has impacts on pH and Dissolved Oxygen (DO) of the ambient water to facilitate integrated pisciculture. The paper suggests that alga-culture has unrealized potentials in carbon sequestration and can be significantly used for extraction of Biodiesel.


Author(s):  
Ole Bennike ◽  
Anker Weidick

NOTE: This article was published in a former series of GEUS Bulletin. Please use the original series name when citing this article, for example: Bennike, O., & Weidick, A. (1999). Observations on the Quaternary geology around Nioghalvfjerdsfjorden, eastern North Greenland. Geology of Greenland Survey Bulletin, 183, 56-60. https://doi.org/10.34194/ggub.v183.5205 _______________ In North and North-East Greenland, several of the outlet glaciers from the Inland Ice have long, floating tongues (Higgins 1991). Nioghalvfjerdsfjorden (Fig. 1) is today occupied by a floating outlet glacier that is about 60 km long, and the fjord is surrounded by dissected plateaux with broad valleys (Thomsen et al. 1997). The offshore shelf to the east of Nioghalvfjerdsfjorden is unusually broad, up to 300 km wide (Cherkis & Vogt 1994), and recently small low islands were discovered on the western part of this shelf (G. Budeus and T.I.H. Andersson, personal communications 1998). Quaternary deposits are widespread around Nioghalvfjerdsfjorden and include glacial, glaciofluvial, marine, deltaic and ice lake deposits. Ice margin features such as kame deposits and moraines are also common (Davies 1972). The glaciation limit increases from 200 m a.s.l. over the eastern coastal islands to 1000 m in the inland areas; local ice caps and valley glaciers are common in the region, although the mean annual precipitation is only about 200 mm per year. Most of the sea in the area is covered by permanent sea ice, with pack ice further east, but open water is present in late summer in some fjords north of Nioghalvfjerdsfjorden, and in the Nordøstvandet polynia.


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