| 1. |
- Al-Handal, Adil Y, 1952, et al.
(författare)
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Gomphonemopsis ligowskii, a new diatom (Bacillariophyceae) from the marine Antarctic and a comparison to other Gomphonemopsis
- 2018
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Ingår i: Diatom Research. - : Informa UK Limited. - 0269-249X .- 2159-8347. ; 33:1, s. 97-103
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Tidskriftsartikel (refereegranskat)abstract
- A new marine diatom, Gomphonemopsis ligowskii, is described. Gomphonemopsis ligowskii was found as an epiphyte on the brown macrophyte, Desmarestia anceps, collected from King George Island, Antarctica in January 2016. This species is the first of the genus described from a polar region. It is a small and relatively rare taxon that is characterized by its unique shape and the presence of uniseriate striae, composed of round poroidal areolae on its valve face. The striae are arranged in parallel rows on either side of the axial area, and a row of rounded areolae on both sides of the valve mantle is confined to the wider part of the valve (headpole). A description of valve ultrastructure as well as a comparison with related taxa are provided.
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| 2. |
- Al-Handal, Adil Y, 1952, et al.
(författare)
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- Nitzschia biundulata sp. Nov. a new sea ice diatom (bacillariophyceae) from the ross sea, Antarctica
- 2019
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Ingår i: Nova Hedwigia: Zeitschrift für Kryptogamenkunde. - : Schweizerbart. - 0029-5035. ; 108:3-4
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Tidskriftsartikel (refereegranskat)abstract
- - A new marine diatom species, Nitzschia biundulata is described. This species was collected and isolated from the ice cover in the Amundsen Sea, Antarctica during the Austral summer, 2011. The description is based on light and scanning electron microscopes examination as well as molecular analysis including 18S SSU rRNA and rbcL. Morphologically, N. biundulata is characterized by having two extensions of the valve margin in a form of two unequal undulations that are not seen in other taxa of the genus. Molecular sequence data indicated similarity with several Nitzschia species such as Nitzschia apiculata, N. palea, N. capitellata as well as Bacillaria paxillifer. Interestingly, large similarity was found with endosymbiont diatom associated with the dinophyte Peridinium balticum. A comparison with the most related species is provided. © 2019 J. Cramer in Gebrüder Borntraeger Verlagsbuchhandlung, Stuttgart, Germany.
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| 3. |
- Al-Handal, Adil Y, 1952, et al.
(författare)
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Observations on diatoms inhabiting natural and artificial substrates in Kongsfjorden, Svalbard, the Arctic
- 2016
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Ingår i: Polar Biology. - : Springer Science and Business Media LLC. - 0722-4060 .- 1432-2056. ; 39:11, s. 1913-1932
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Tidskriftsartikel (refereegranskat)abstract
- The most dramatic effects of global climate change are predicted for the Arctic, and there is a raising concern about the lack of baseline information on microalgal biodiversity. The present study was motivated by the general lack of information on species distribution of Arctic benthic diatoms and particularly studies providing photographs to facilitate morphological species identification. Diatoms were studied in samples collected from Ny lesund, Spitsbergen, Svalbard, during summer 2006 and spring 2008. Two types of samples were examined: diatoms scraped from ceramic tiles, immersed at 0.5 m depth (2006), and diatoms extracted from surface sediment, collected at 0.5 to 3 m depth (2008). A total number of 75 taxa belonging to 45 genera were encountered. Sixty-eight species were found in the sediment samples and 48 on the ceramic tiles, of which 41 species were found on both substrata. Common species of the tile assemblages were Fragilariopsis spp., Licmophora spp., Odontella aurita, Synedropsis hyperborea and Trachyneis aspera, while Thalassiosira spp., Diploneis spp. and Navicula spp. were common in the sediment samples. Twenty-five percent of the observed diatom species belonged to freshwater taxa brought to the fjord from surrounding meltwater and river discharges. ELMANN A, 1992, DEEP-SEA RESEARCH PART A-OCEANOGRAPHIC RESEARCH PAPERS, V39, PS525
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| 4. |
- Al-Handal, Adil Y, 1952, et al.
(författare)
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Two new marine species of Cocconeis (Bacillariophyceae) from the west coast of Sweden
- 2019
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Ingår i: European Journal of Taxonomy. - : Museum National D'Histoire Naturelle. - 2118-9773. ; 497, s. 1-16
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Tidskriftsartikel (refereegranskat)abstract
- This paper is part of a project of studying benthic diatom biodiversity on marine coastal regions of Sweden with focus on rare and less known species. Two new species of Cocconeis Ehrenb. are described from Vrango, a small island in the west coast of Sweden. Both species were found as epiphytic on the green alga Ulva intestinalis L. Cocconeis magnoareolata Al-Handal, Riaux-Gob., R.Jahn & A.K.Wulff sp. nov. is a small species not exceeding 9 mu m in length and characterized by having large subquadrangular areolae on the sternum valve. Cocconeis vrangoensis Al-Handal & Riaux-Gob. sp. nov. appears similar to some taxa of the 'Cocconeis scutellum complex', but differs by its stria density on both valves and variable features of the areola and valvocopula ultrastructure. Detailed descriptions based on light and electron microscopy examination, a comparison with closely related taxa, as well as a description of the habitat of both species are here presented.
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| 5. |
- Ever Aguirre, Luis, et al.
(författare)
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Diatom frustules protect DNA from ultraviolet light
- 2018
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Ingår i: Scientific Reports. - : Springer Science and Business Media LLC. - 2045-2322. ; 8:1
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Tidskriftsartikel (refereegranskat)abstract
- The evolutionary causes for generation of nano and microstructured silica by photosynthetic algae are not yet deciphered. Diatoms are single photosynthetic algal cells populating the oceans and waters around the globe. They generate a considerable fraction (20-30%) of all oxygen from photosynthesis, and 45% of total primary production of organic material in the sea. There are more than 100,000 species of diatoms, classified by the shape of the glass cage in which they live, and which they build during algal growth. These glass structures have accumulated for the last 100 million of years, and left rich deposits of nano/microstructured silicon oxide in the form of diatomaceous earth around the globe. Here we show that reflection of ultraviolet light by nanostructured silica can protect the deoxyribonucleic acid (DNA) in the algal cells, and that this may be an evolutionary cause for the formation of glass cages. © 2018 The Author(s).
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| 6. |
- Fransson, Agneta, 1964, et al.
(författare)
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CO2-system development in young sea ice and CO2 gas exchange at the ice/air interface mediated by brine and frost flowers in Kongsfjorden, Spitsbergen
- 2015
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Ingår i: Annals of Glaciology. - 0260-3055. ; 56:69, s. 245-257
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Tidskriftsartikel (refereegranskat)abstract
- In March and April 2010, we investigated the development of young landfast sea ice in Kongsfjorden, Spitsbergen, Svalbard. We sampled the vertical column, including sea ice, brine, frost flowers and sea water, to determine the CO2 system, nutrients, salinity and bacterial and ice algae production during a 13 day interval of ice growth. Apart from the changes due to salinity and brine rejection, the sea-ice concentrations of total inorganic carbon (C T), total alkalinity (A T), CO2 and carbonate ions (CO3 2–) in melted ice were influenced by dissolution of calcium carbonate (CaCO3) precipitates (25–55 μmol kg–1) and played the largest role in the changes to the CO2 system. The C T values were also influenced by CO2 gas flux, bacterial carbon production and primary production, which had a small impact on the C T. The only exception was the uppermost ice layer. In the top 0.05 m of the ice, there was a CO2 loss of ∼20 μmol kg–1 melted ice (1 mmol m–2) from the ice to the atmosphere. Frost flowers on newly formed sea ice were important in promoting ice–air CO2 gas flux, causing a CO2 loss to the atmosphere of 140–800 μmol kg–1 d–1 melted frost flowers (7–40 mmol m–2 d–1).
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| 7. |
- Halbach, Laura, et al.
(författare)
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Tidewater Glaciers and Bedrock Characteristics Control the Phytoplankton Growth Environment in a Fjord in the Arctic
- 2019
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Ingår i: Frontiers in Marine Science. - : Frontiers Media SA. - 2296-7745. ; 6
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Tidskriftsartikel (refereegranskat)abstract
- Meltwater discharge from tidewater glaciers impacts the adjacent marine environment. Due to the global warming, tidewater glaciers are retreating and will eventually terminate on land. Yet, the mechanisms through which meltwater runoff and subglacial discharge from tidewater glaciers influence marine primary production remain poorly understood, as data in close proximity to glacier fronts are scarce. Here, we show that subglacial meltwater discharge and bedrock characteristics of the catchments control the phytoplankton growth environment inside the fjord, based on data collected in close proximity to tidewater glacier fronts in Kongsfjorden, Svalbard from 26 to 31 July 2017. In the southern part of the inner fjord, glacial meltwater from subglacial discharge was rich in fine sediments derived from erosion of Devonian Old Red Sandstone and carbonate rock deposits, limiting light availability for phytoplankton (0.6 mg m(-3) Chl a on average, range 0.2-1.9 mg m(-3)). In contrast, coarser sediments derived from gneiss and granite bedrock and lower subglacial discharge rates were associated with more favourable light conditions facilitating a local phytoplankton bloom in the northern part of the inner fjord with mean Chl a concentration of 2.8 mg m(-3) (range 1.3-7.4 mg m(-3)). In the northern part, glacier meltwater was a direct source of silicic acid through weathering of the silica-rich gneiss and granite bedrock. Upwelling of the subglacial freshwater discharge plume at the Kronebreen glacier front in the southern part entrained large volumes of ambient, nutrient-rich bottom waters which led to elevated surface concentrations of ammonium, nitrate, and partly silicic acid. Total dissolved inorganic nitrogen transported to the surface with the upwelling of the subglacial discharge plume has a significant potential to enhance summer primary production in Kongsfjorden, with ammonium released from the seafloor being of particular importance. The transition from tidewater to land-terminating glaciers may, thus, reduce the input of nutrients to the surface layer with negative consequences for summer productivity.
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| 8. |
- Hoffmann, R., et al.
(författare)
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Implications of Glacial Melt-Related Processes on the Potential Primary Production of a Microphytobenthic Community in Potter Cove (Antarctica)
- 2019
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Ingår i: Frontiers in Marine Science. - : Frontiers Media SA. - 2296-7745. ; 6:October
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Tidskriftsartikel (refereegranskat)abstract
- The Antarctic Peninsula experiences a fast retreat of glaciers, which results in an increased release of particles and sedimentation and, thus, a decrease in the available photosynthetic active radiation (PAR, 400-700 nm) for benthic primary production. In this study, we investigated how changes in the general sedimentation and shading patterns affect the primary production by benthic microalgae, the microphytobenthos. In order to determine potential net primary production and respiration of the microphytobenthic community, sediment cores from locations exposed to different sedimentation rates and shading were exposed to PAR of 0-70 mu.mol photons m(-2)s(-1). Total oxygen exchange rates and microphytobenthic diatom community structure, density, and biomass were determined. Our study revealed that while the microphytobenthic diatom density and composition remained similar, the net primary production of the microphytobenthos decreased with increasing sedimentation and shading. By comparing our experimental results with in situ measured PAR intensities, we furthermore identified microphytobenthic primary production as an important carbon source within Potter Cove's benthic ecosystem. We propose that the microphytobenthic contribution to the total primary production may drop drastically due to Antarctic glacial retreat and related sedimentation and shading, with yet unknown consequences for the benthic heterotrophic community, its structure, and diversity.
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| 9. |
- Leu, E., et al.
(författare)
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A (too) bright future? Arctic diatoms under radiation stress
- 2016
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Ingår i: Polar Biology. - : Springer Science and Business Media LLC. - 0722-4060 .- 1432-2056. ; 39:10, s. 1711-1724
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Tidskriftsartikel (refereegranskat)abstract
- Decreasing Arctic sea ice cover and increasing stratification of ocean surface waters make the exposure of pelagic microalgae to high irradiances more likely. Apart from light being a necessary prerequisite for photosynthesis, rapidly changing and/or high irradiances are potentially detrimental. An in situ study was performed in the high Arctic (79A degrees N) to determine the effect of high irradiances in general, and ultraviolet radiation (UVR, 280-400 nm) in particular, on cell concentrations, fatty acid composition, and photoprotective pigments of three diatom species isolated from seawater around Svalbard. Unialgal cultures were exposed in situ at 0.5- and 8 m-depth. After 40 h, cell concentrations of Synedropsis hyperborea and Thalassiosira sp., were lower at 0.5 than at 8 m, and the content of the photoprotective xanthophyll-cycle pigment diatoxanthin in all species (S. hyperborea, Thalassiosira sp., Porosira glacialis) was higher in the 0.5 m exposure compared to 8 m. In S. hyperborea, growth was additionally inhibited by UVR at 0.5-m depth. In situ radiation conditions led, furthermore, to a significant decrease in polyunsaturated fatty acids (PUFAs) in all three species, but UVR had no additional effect. Hence, we conclude that natural radiation conditions close to the surface could reduce growth and PUFA concentrations, but the effects are species specific. The diatoms' potential to acclimate to these conditions over time has to be evaluated.
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| 10. |
- Olofsson, Malin, et al.
(författare)
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Limited response of a spring bloom community inoculated with filamentous cyanobacteria to elevated temperature and pCO2
- 2019
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Ingår i: Botanica Marina. - : Walter de Gruyter GmbH. - 0006-8055 .- 1437-4323. ; 62:1
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Tidskriftsartikel (refereegranskat)abstract
- Temperature and CO2 levels are projected to increase in the future, with consequences for carbon and nutrient cycling in brackish environments, such as the Baltic Sea. Moreover, filamentous cyanobacteria are predicted to be favored over other phytoplankton groups under these conditions. Under a 12-day outdoor experiment, we examined the effect on a natural phytoplankton spring bloom community of elevated temperature (from 1°C to 4°C) and elevated pCO2 (from 390 to 970 μatm). No effects of elevated pCO2 or temperature were observed on phytoplankton biovolumes, but a significantly higher photosystem II activity was observed at elevated temperature after 9 days. In addition, three species of diazotrophic filamentous cyanobacteria were inoculated to test their competitive capacity under spring bloom conditions. The toxic cyanobacterium Nodularia spumigena exhibited an average specific growth rate of 0.10 d−1 by the end of the experiment, indicating potential prevalence even during wintertime in the Baltic Sea. Generally, none of the inoculated cyanobacteria species were able to outcompete the natural phytoplankton species at temperatures ≤4°C. No direct effects were found on heterotrophic bacteria. This study demonstrates the highly efficient resistance towards short-term (12 days) changes in abiotic factors by the natural Baltic Sea spring bloom community.
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