| 1. |
- Abrahamsson, Katarina, 1957, et al.
(författare)
-
Air-sea exchange of halocarbons: the influence of diurnal and regional variations and distribution of pigments
- 2004
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Ingår i: Deep-Sea Research Part Ii-Topical Studies in Oceanography. - : Elsevier BV. - 0967-0645. ; 51:22-24, s. 2789-2805
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Tidskriftsartikel (refereegranskat)abstract
- Diurnal cycles of halocarbons, except methyl bromide and methyl chloride, were observed at six 24-h stations occupied in three different regions, the Summer Ice Edge, the Winter Ice Edge, and the Antarctic Polar Front, in the Atlantic sector of the Southern Ocean during a Swedish-South African expedition in 1997/1998. The diurnal cycles contained three phases; a productive phase, a phase of losses and a phase with steady state. The duration of the different phases varied for the different stations as well as for individual compounds. The measured production and losses of organo-halogens in the Antarctic Ocean based on values from each station, were in the order of a few to hundreds of Tg yr(-1). Bromochloromethane, tribromomethane, trichloroethene and diiodomethane were the four compounds found in highest concentrations throughout the investigation, and they were found to be the major contributors of organohalogens. Only the presence of the photosynthetic pigment 19'-hexanoyloxyfucoxanthin, biomarker pigment of haptophytes, could explain some of the variations in the distribution and production of halocarbons, and then only for iodinated compounds. The flux of organo-halogens from the oceans to the atmosphere was estimated in two ways, either based on calculations according to models or based on the measured concentrations. Large discrepancies were found, which could not be explained by chemical or biological degradation or adsorption to particles. This investigation, therefore, shows the need for assessing the rates of degradation and the air-sea exchange more accurately. (C) 2004 Elsevier Ltd. All rights reserved.
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| 2. |
- Al-Handal, Adil Y, 1952, et al.
(författare)
-
A new species of Craspedostauros (Bacillariophyceae) from the west coast of Sweden, with taxonomic and ecological notes on Craspedostauros laevissimus
- 2024
-
Ingår i: Botanica Marina. - 0006-8055 .- 1437-4323. ; 67:1, s. 51-60
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Tidskriftsartikel (refereegranskat)abstract
- Since its separation from Stauroneis in 1999, several new species of Craspedostauros were discovered in a variety of habitats and geographic locations, adding morphological and phylogenetic data to the investigations of the genus. In a survey of littoral diatoms of Sweden, both on the west and east coasts, two epiphytic stauros-bearing species were encountered and assigned to Craspedostauros following the characteristic features of this genus, including the possession of a stauros narrower than the central area and cribrate areolae. One species is described as new to science; Craspedostauros lateralis sp. nov., and the other is of uncertain identity but bears morphological similarity to C. laevissimus. Caspedostauros lateralis is a marine epiphytic species found in the west coast of Sweden, off Gothenburg city. Based on light and electron microscopy, a detailed description of the morphological and ultrastructural features of these species is given and a comparison of the distinguishing characters with allied species is discussed. Some ecological data and the occurrence of associated species on the host macrophyte are provided.
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| 3. |
- Al-Handal, Adil Y, 1952, et al.
(författare)
-
COCCONEIS POTTERCOVEI SP NOV AND COCCONEIS PINNATA VAR. MATSII VAR. NOV., TWO NEW MARINE DIATOM TAXA FROM KING GEORGE ISLAND, ANTARCTICA
- 2010
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Ingår i: Diatom Research. - 0269-249X. ; 25:1, s. 1-11
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Tidskriftsartikel (refereegranskat)abstract
- Details of two new small marine taxa of the genus Cocconeis Ehrenberg are described; C. pottercovei sp. nov. and C. pinnata var. matsii var. nov., which were observed as epipelic and epiphytic in Potter Cove, King George Island, Antarctica. Descriptions are based on both light and scanning electron microscope observations. C. pottercovei belongs to the group of Cocconeis taxa that bear very short and marginal striae on the rapheless valve while C. pinnata var. matsii belongs to the C. costata Gregory complex. They are mainly differentiated from the other similar taxa by stria number, stria arrangement and structure on both raphe and rapheless valves. A comparison with closely resembling taxa is given.
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| 4. |
- Al-Handal, Adil Y, 1952, et al.
(författare)
-
Entomoneis annagodheisp. nov., a new marine diatom (Entomoneidaceae, Bacillariophyta) from the west coast of Sweden
- 2020
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Ingår i: Diatom Research. - : Informa UK Limited. - 0269-249X .- 2159-8347. ; 35:3, s. 269-279
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Tidskriftsartikel (refereegranskat)abstract
- The genusEntomoneisincludes diatoms with an elevated bilobate keel, a sigmoid raphe canal and numerous girdle bands. It is known to inhabit various environments, from freshwater to marine, both plankton and benthos. During a phytoplankton investigation in the Kungalv estuary on the west coast of Sweden, we observed numerous cells belonging toEntomoneis. Further morphological investigations performed with light and electron microscopy allowed us to describeEntomoneis annagodhei, sp. nov., with a unique set of morphological characters. Most importantly, a still undocumented character proved to be an oblique transapical fascia across the centre of the valve. Other distinctive features of this species are a pronounced raphe canal with dense raphe fibulae, very fine striation, resolvable only with electron microscopy, external lanceolate slit-like opening of the central nodule, and fine, linear to undulate external ridges running more or less parallel and adjacent to the raphe and valve margin. The morphological characters and morphometry are discussed in comparison with similar taxa. Our results contribute to the under-appreciated diversity ofEntomoneis, especially inhabiting the marine plankton.
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| 5. |
- Al-Handal, Adil Y, 1952, et al.
(författare)
-
Entomoneis grisslehamnensis, a New Diatom (Bacillariophyceae) from the Baltic Coast of Sweden with taxonomic and ecological notes on Entomoneis paludosa (W. Smith) Reimer
- 2023
-
Ingår i: Diatom Research. - 0269-249X. ; 38:1, s. 55-68
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Tidskriftsartikel (refereegranskat)abstract
- The diatom genus Entomoneis includes species with panduriform frustules characterized by a bilobate, elevated keel, sigmoid raphe canal and numerous open, porous girdle bands. During a phytoplankton survey along the Baltic coast of Sweden, we observed numerous Entomoneis cells, some belonging to the well-known Entomoneis paludosa, while others remained unknown. Morphological and ultrastructural studies of the unknown species were performed with light microscopy (LM), scanning (SEM) and transmission (TEM) electron microscopy, and revealed a unique set of morphological characters. Live cells of Entomoneis grisslehamnensis sp. nov. contain one plate-like plastid and show various degrees of torsion about the apical axis. Microscopic features of cleaned frustules are discussed in comparison with similar species. Most importantly, every 2nd to 5th virga is strongly elevated, uniseriate striae are composed of quadrangular areolae with finely perforated hymenes; the winged keel with a discernible raphe canal is structurally strengthened by raphe fibulae with a flattened wing area, and the main part of the valve bulges towards the margins; striation is decussate on the wings and there is one row of raphe canal areolae at the central area. In addition to describing this new species of an underappreciated, yet cosmopolitan diatom genus, we contribute to the taxonomy of E. paludosa with LM, SEM and TEM details, some of which were not sufficiently noted in original descriptions or re-examination of type material and other specimens made by Dalu et al. [2015. A re-examination of the type material of Entomoneis paludosa (W. Smith) Reimer and its morphology and distribution in African waters. Fottea 15: 11-25] and Long et al. [2022. Ultrastructure of three species of Entomoneis (Bacillariophyta) from Lake Qinghai of China, with reference to the external areola occlusions.
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| 6. |
- Al-Handal, Adil Y, 1952, et al.
(författare)
-
Fallacia fawensis sp. nov., a new brackish water diatom (Bacillariophyceae) from Southern Iraq
- 2022
-
Ingår i: Phytotaxa. - : Magnolia Press. - 1179-3155 .- 1179-3163. ; 550:1, s. 71-78
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Tidskriftsartikel (refereegranskat)abstract
- The diatom genus Fallacia includes species having a conopeum which is a perforated thin sheath of silica lying along the apical axis on the external valve face and a hyaline lateral area in the internal valve face. In surveying the benthic diatoms of Basra, a new small brackish water species, Fallacia fawensis was found associated with fine-grained substrata on the western bank of Shatt Al???Arab River, Southern Iraq. This epipelic species is described based on light and scanning electron microscopy and characterized by having a porous conopeum covering the area between raphe sterna and mantle, narrow elongated marginal striae, and a structure similar to lateral hyaline areas in the valve internal side. The terminal raphe endings on the external valve face, below valve apex, the raphe sternum inner margins come close to each other, blocking raphe canal but leaving a lacuna-like thin groove for connection with the deflected upper part of the open raphe canal. These features separated this species from allied taxa of the genus and also from closely related genera, Pseudofallacia and Germaniella. Notes on the ecology and distribution of the new species as well as the associated diatom taxa are provided.
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| 7. |
- Al-Handal, Adil Y, 1952, et al.
(författare)
-
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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| 8. |
- Al-Handal, Adil Y, 1952, et al.
(författare)
-
Marine benthic diatoms from Potter Cove, King George Island, Antarctica
- 2008
-
Ingår i: Botanica Marina. - 0006-8055. ; 51:1, s. 51-68
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Tidskriftsartikel (refereegranskat)abstract
- Antarctic benthic marine diatoms from the Potter Cove region, King George Island were studied in samples collected during the austral summer 2003. A floristic list was made to add information on the Antarctic benthic diatom distribution. A total of 84 species was identified from four localities in Potter Cove, the majority of which are of cosmopolitan distribution. The most common taxa encountered were Cocconeis spp., Gyrosigma fasciola, Navicula cf. cancellata, N. cf. perminuta, Petroneis plagiostoma and Pleurosigma obscurum. Both G. fasciola and P. obscurum are recorded for the first time from Antarctica with such common occurrence. The overall diatom population in Potter Cove appeared rather different from other diatom populations observed in Antarctic marine habitats.
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| 9. |
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| 10. |
- Al-Handal, Adil Y, 1952, et al.
(författare)
-
Mastogloia jahniae sp. nov., a new diatom (Bacillariophyceae) from the Baltic Sea coast of Sweden
- 2021
-
Ingår i: Phytotaxa. - : Magnolia Press. - 1179-3155 .- 1179-3163. ; 484:1, s. 121-128
-
Tidskriftsartikel (refereegranskat)abstract
- Described is here Mastogloia jahniae sp. nov. a species new to science from Skatan on the Baltic Sea, east coast of Sweden. Description of this new species is based on light and scanning electron microscopy. The new species is classified in the Mastogloia section Ellipticae and is characterized by having radiating short and long striae around the central area, sinuous raphe branches and partecta displaced toward the middle of the valve by a siliceous flange. M. jahniae sp. nov. in terms of size is rather small whereas in terms of ecology appears an epipelic brackish water species. The new species was rather rare in all samples collected from Skatan and has not been found in the other adjacent regions sampled. A comparison with similar established Mastogloia species is provided.
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| 11. |
- Al-Handal, Adil Y, 1952, et al.
(författare)
-
Navithidium gen. nov., a new monoraphid diatom (Bacillariophyceae) genus based on Achnanthes delicatissima Simonsen
- 2021
-
Ingår i: Diatom Research. - 0269-249X. ; 36:2, s. 133-141
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Tidskriftsartikel (refereegranskat)abstract
- We investigated the ultrastructure of Achnanthes delicatissima Simonsen in materials collected from the Swedish Baltic coast. Valve structure differs markedly from that of Achnanthes sensu lato, particularly in the absence of cribrate areolae which separates Achnanthes from all other members of the family Achnanthaceae. Comparing this species with those recently described achnanthoid genera, such as Scalariella Riaux-Gobin & Witkowski and Madinithidium Witkowski, Desrosiers & Riaux-Gobin revealed morphological differences that warrant the erection of a new genus, Navithidium. Owing to the small size of the frustules, it is difficult to identify Navithidium delicatissima in light microscopy due to similarities with some closely related taxa like Achnanthidium pseudochamaepinnularia (which is here transferred to Navithidium). A comparison with related genera is provided and discussed. © 2021 The Author(s). Published by Informa UK Limited, trading as Taylor & Francis Group.
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| 12. |
- Al-Handal, Adil Y, 1952, et al.
(författare)
-
- Nitzschia biundulata sp. Nov. a new sea ice diatom (bacillariophyceae) from the ross sea, Antarctica
- 2019
-
Ingår i: Nova Hedwigia: Zeitschrift für Kryptogamenkunde. - : Schweizerbart. - 0029-5035. ; 108:3-4
-
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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| 13. |
- 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
-
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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| 14. |
- Al-Handal, Adil Y, 1952, et al.
(författare)
-
Revisiting Potter Cove, King George Island, Antarctica, 12 years later: new observations of marine benthic diatoms
- 2022
-
Ingår i: Botanica Marina. - : Walter de Gruyter GmbH. - 0006-8055 .- 1437-4323. ; 65:2, s. 81-103
-
Tidskriftsartikel (refereegranskat)abstract
- Continuous observations of Antarctic benthic diatoms are necessary to detect changes in species composition and biodiversity that may result from environmental changes. The present work provides a systematic list of benthic diatoms from Potter Cove (62.03 degrees S 58.35 degrees W) collected during summer 2015. The new findings are compared with observations made 12 years ago (summer 2003). In total, 80 taxa were found, similar to that encountered earlier, but 17 species (21% of the total species number) were not observed in 2003, and 26 species (31%) of those reported in 2003 did not appear in 2015. The dominant species in 2003 and 2015 was the large epipelic and cosmopolitan Gyrosigma fasciola. Most of the species either newly observed in the present study, or absent in the present study but observed previously, occurred either rarely or very rarely. Gyrosigma arcuatum and Pleurosigma diversestriatum were newly observed in 2015 and not previously reported from polar regions. This study provides systematic and ecological information on all taxa encountered and is illustrated with light microscopy and scanning electron microscopy (SEM) images. We emphasize that ice-inhabiting and other benthic diatoms should be included when considering the biodiversity of polar diatoms. Thus, we hope that the present study will add a piece to the puzzle of climate change effects on the benthic diatoms in this vulnerable region and will complement earlier published species records in the area.
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| 15. |
- Al-Handal, Adil Y, 1952, et al.
(författare)
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Rhoicosphenia johannessoniae (Bacillariophyceae), a new diatom from the Swedish coast of the Baltic Sea
- 2023
-
Ingår i: Phytotaxa. - 1179-3155 .- 1179-3163. ; 618:1, s. 69-78
-
Tidskriftsartikel (refereegranskat)abstract
- Rhoicosphenia is a relatively small diatom genus regarding the number of species and the genus is characterized by its wedge-shaped frustule and heterovalvar structure. It is one of the few genera that is distributed in both marine and freshwater habitats. Few species of Rhoicosphenia are known along the stretched Baltic Sea coast of Sweden. The present study describes a new epiphytic species of Rhoicosphenia from the brackish water of Grisslehamn in the northern part of the Baltic Sea. Rhoicosphenia johannessoniae sp. nov. appears closely related to R. baltica, but differs in having more elongated and protracted base pole, densely packed areolae and a central area located below the central part of the valve. Detailed descriptions of the species based on light and electron microscopy, as well as a comparison with related taxa, are provided. The present work is part of a larger project aiming to study the littoral diatoms of Sweden. The finding of this species, together with other species previously described within the project, will add to our knowledge of the diatom assemblages of the Baltic Sea which seems to have a richer flora than earlier anticipated.
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| 16. |
- Al-Handal, Adil Y, 1952, et al.
(författare)
-
Synedropsis abuflosensis sp. nov., a new araphid diatom (Bacillariophyceae) from the Shatt Al-Arab River, Southern Iraq
- 2022
-
Ingår i: Cryptogamie Algologie. - : Museum National d'Histoire Naturelle, Paris, France. - 0181-1568. ; 43:2, s. 31-39
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Tidskriftsartikel (refereegranskat)abstract
- Synedropsis abuflosensis sp. nov. is the third species of the genus recorded from a sub-tropical brackish water habitat as opposed to a polar distribution. This species is differentiated from others in the genus by having a different number of slits in the apical slit field at opposite ends of the valve (i.e., 4 at the end possessing a rimoportula versus 5 at the end lacking a rimoportula), an apically oriented rimoportula and 3-4 non-porous cingular bands. Its habitat is different than that of all known Synedropsis Hasle, Medlin & Syvertsen species as it is either benthic or epiphytic in algal mats rather than planktonic or associated with sea ice. The new species was found in waters with a conductivity of 7.1 mu S (cm-1) (salinity 3.3 psu) and a temperature of 33 degrees C. Morphological characters of the new species are described based on light and scanning electron microscopy observations. A comparison of S. abuflosensis sp. nov. with morphologically similar species is provided.
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| 17. |
- Al-Handal, Adil Y, 1952, et al.
(författare)
-
Two new marine species of Cocconeis (Bacillariophyceae) from the west coast of Sweden
- 2019
-
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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| 18. |
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| 19. |
- Bandara, T M W J, 1968, et al.
(författare)
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Diatom frustules enhancing the efficiency of gel polymer electrolyte based dye-sensitized solar cells with multilayer photoelectrodes
- 2020
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Ingår i: Nanoscale Advances. - : Royal Society of Chemistry (RSC). - 2516-0230. ; 2:1, s. 199-209
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Tidskriftsartikel (refereegranskat)abstract
- The incorporation of nanostructures that improve light scattering and dye adsorption has been suggested for dye-sensitized solar cells (DSSCs), but the manufacture of photonic and nanostructured materials with the desired properties is not an easy task. In nature, however, the process of light-harvesting for photosynthesis has, in some cases, evolved structures with remarkable wavelength-sensitive light-trapping properties. The present work is focused on enhancing the efficiency of quasi solid-state DSSCs by capitalizing on the light trapping properties of diatom frustules since they provide complex 3-dimensional structures for scattering and trapping light. This study reports a promising approach to prepare TiO2 nanocrystal (14 nm) based photo-electrodes by utilizing the waveguiding and photon localization effects of nanostructured diatom frustules for enhancing light harvesting without deteriorating the electron conduction. Single and double-layered photo-electrodes were prepared with different frustule/nanocrystal combinations and conformations on transparent conductive oxide substrates. This study clearly reports impressive efficiency and short circuit current density enhancements of about 35% and 39%, respectively, due to the incorporation of diatom frustules extracted from a ubiquitous species. The SEM images obtained in this work reveal that the produced thin films had a remarkable surface coverage of evenly distributed frustules within the TiO2 nanoparticle layer. To the best of our knowledge, this study reports the first quasi solid-state DSSC based on a photo-electrode with incorporated bio-formed nanostructures.
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| 20. |
- Björkman, Anne, 1981, et al.
(författare)
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A reflection on four impactful Ambio papers: The biotic perspective This article belongs to Ambio's 50th Anniversary Collection. Theme: Climate change impacts
- 2021
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Ingår i: Ambio. - : Springer Science and Business Media LLC. - 0044-7447 .- 1654-7209. ; 50, s. 1145-1149
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Tidskriftsartikel (refereegranskat)abstract
- Climate change represents one of the most pressing societal and scientific challenges of our time. While much of the current research on climate change focuses on future prediction, some of the strongest signals of warming can already be seen in Arctic and alpine areas, where temperatures are rising faster than the global average, and in the oceans, where the combination of rising temperatures and acidification due to increased CO2 concentrations has had catastrophic consequences for sensitive marine organisms inhabiting coral reefs. The scientific papers highlighted as part of this anniversary issue represent some of the most impactful advances in our understanding of the consequences of anthropogenic climate change. Here, we reflect on the legacy of these papers from the biotic perspective.
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| 21. |
- Braeckman, U., et al.
(författare)
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Glacial melt disturbance shifts community metabolism of an Antarctic seafloor ecosystem from net autotrophy to heterotrophy
- 2021
-
Ingår i: Communications Biology. - : Springer Science and Business Media LLC. - 2399-3642. ; 4:1
-
Tidskriftsartikel (refereegranskat)abstract
- Climate change-induced glacial melt affects benthic ecosystems along the West Antarctic Peninsula, but current understanding of the effects on benthic primary production and respiration is limited. Here we demonstrate with a series of in situ community metabolism measurements that climate-related glacial melt disturbance shifts benthic communities from net autotrophy to heterotrophy. With little glacial melt disturbance (during cold El Nino spring 2015), clear waters enabled high benthic microalgal production, resulting in net autotrophic benthic communities. In contrast, water column turbidity caused by increased glacial melt run-off (summer 2015 and warm La Nina spring 2016) limited benthic microalgal production and turned the benthic communities net heterotrophic. Ongoing accelerations in glacial melt and run-off may steer shallow Antarctic seafloor ecosystems towards net heterotrophy, altering the metabolic balance of benthic communities and potentially impacting the carbon balance and food webs at the Antarctic seafloor. Ulrike Braeckman et al. use in situ benthic community and benthic biogeochemistry measurements in Potter Cove on the Antarctic Peninsula to show that climate-related glacial melt disturbance shifts benthic communities from net autotrophy to heterotrophy. This study sheds light on how future glacial melt and run-off may affect the metabolic balance of Antarctic benthic communities.
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| 22. |
- Burford, M. A., et al.
(författare)
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Perspective: Advancing the research agenda for improving understanding of cyanobacteria in a future of global change
- 2020
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Ingår i: Harmful Algae. - : Elsevier BV. - 1568-9883. ; 91
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Tidskriftsartikel (refereegranskat)abstract
- Harmful cyanobacterial blooms (=cyanoHABs) are an increasing feature of many waterbodies throughout the world. Many bloom-forming species produce toxins, making them of particular concern for drinking water supplies, recreation and fisheries in waterbodies along the freshwater to marine continuum. Global changes resulting from human impacts, such as climate change, over-enrichment and hydrological alterations of waterways, are major drivers of cyanoHAB proliferation and persistence. This review advocates that to better predict and manage cyanoHABs in a changing world, researchers need to leverage studies undertaken to date, but adopt a more complex and definitive suite of experiments, observations, and models which can effectively capture the temporal scales of processes driven by eutrophication and a changing climate. Better integration of laboratory culture and field experiments, as well as whole system and multiple-system studies are needed to improve confidence in models predicting impacts of climate change and anthropogenic over-enrichment and hydrological modifications. Recent studies examining adaptation of species and strains to long-term perturbations, e.g. temperature and carbon dioxide (CO 2 ) levels, as well as incorporating multi-species and multi-stressor approaches emphasize the limitations of approaches focused on single stressors and individual species. There are also emerging species of concern, such as toxic benthic cyanobacteria, for which the effects of global change are less well understood, and require more detailed study. This review provides approaches and examples of studies tackling the challenging issue of understanding how global changes will affect cyanoHABs, and identifies critical information needs for effective prediction and management. © 2019
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| 23. |
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| 24. |
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| 25. |
- Chen, Deliang, 1961, et al.
(författare)
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Attenuation of biologically effective UV doses under overcast skies: a case study from the eastern Atlantic sector of the Southern Ocean
- 2004
-
Ingår i: Deep-Sea Research Part Ii-Topical Studies in Oceanography. - : Elsevier BV. - 0967-0645. ; 51:22-24, s. 2673-2682
-
Tidskriftsartikel (refereegranskat)abstract
- This study deals attenuation of ultraviolet solar radiation measured during the SWEDARP 1997/1998 expedition in the eastern Atlantic sector of the Southern Ocean. Experimental data were measured on board a ship and theoretical computation of radiative transfer has been applied. Focus has been placed on biologically effective UV-B doses using three commonly applied biological weighting functions based on: inhibition of carbon dioxide fixation (Science 258 (1992) 646); Generalized plant effects (Stratospheric Ozone Reduction, Solar Ultraviolet Radiation and Plant Life 1986, Springer, Berlin) and DNA lesions (Proc. Nat. Acad. Sci. USA 71 (1974) 3363). The ratio of measured dose to that under clear sky condition, calculated by a model, was defined as transmittance which was studied in relation to other information. Further, the interrelationship between the biologically effective UV doses and various broadband irradiance in the UV-A, UV-B and PAR was established. It shows that the UV-B doses based on the three weighting functions are closely linked to each other and their cloud transmittances are nearly the same. The biologically effective UV-B doses can be estimated with reasonable accuracy from the broadband irradiance in the UV-A, UV-B and PAR regions, with UV-B giving the best results. Univariate analysis between the transmittance and zenith angle, total cloud cover and cloud base height was performed. It is found that attenuation is almost independent of zenith angle. Transmission is reduced by 7.7% if the cloud cover is increased by one octa. The average transmittance of the UV-B doses is 0.40, indicating that clouds have played an important role in reducing the UV radiation. (C) 2004 Elsevier Ltd. All rights reserved.
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| 26. |
- Croot, P. L., et al.
(författare)
-
Trace metal/phytoplankton interactions in the Skagerrak
- 2002
-
Ingår i: Journal of Marine Systems. - 0924-7963. ; 35:1-2, s. 39-60
-
Tidskriftsartikel (refereegranskat)abstract
- Algal community species composition, as estimated by high performance liquid chromatography (HPLC) pigments and microscopy analysis, and trace metal speciation (Cu and Co) and distributions (Fe, Zn, Co and Cu) were measured along a summer transect across the Skagerrak. In waters of Baltic origin, with elevated trace metals levels, but very low macronutrients, a mix of dinoflagellates and haptophytes dominated the low biomass. In the Jutland current, which had high dissolved iron concentrations, a mixed bloom (4-6 mug/l chl a) of diatoms (major species-Leptocylindricus danica) and dinoflagellates (Ceratium sp.) was present. In the waters of the central Skagerrak derived from the North Sea, below the low salinity Baltic water, a large diatom (major species-L. danica) bloom (7.7 mug/l) was present at 35 in. This bloom formed below the pycnocline. and was located at the nutricline for silicate. The lowest concentrations of trace metals were found in the water of North Sea origin. Synechocoecus-like cyanobacteria were observed in the upper waters across the survey area, as were strong binding ligands for Cu, but no clear numerical relationship existed between them, as had been observed by Moffett [Deep-Sea Res. 42 (1995) 1273]m the Sargasso Sea. The [Co]/[Zn] hypothesis of Sunda and Huntsman [Limnol. Oceanogr, 40 (1995) 1404] for coccolithophorids and diatoms was examined using the field data collected. (C) 2002 Elsevier Science B.V. All rights reserved.
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| 27. |
- De Tommasi, Edoardo, et al.
(författare)
-
Multiple-pathways light modulation in Pleurosigma strigosum bi-raphid diatom
- 2024
-
Ingår i: SCIENTIFIC REPORTS. - 2045-2322. ; 14:1
-
Tidskriftsartikel (refereegranskat)abstract
- Ordered, quasi-ordered, and even disordered nanostructures can be identified as constituent components of several protists, plants and animals, making possible an efficient manipulation of light for intra- and inter- species communication, camouflage, or for the enhancement of primary production. Diatoms are ubiquitous unicellular microalgae inhabiting all the aquatic environments on Earth. They developed, through tens of millions of years of evolution, ultrastructured silica cell walls, the frustules, able to handle optical radiation through multiple diffractive, refractive, and wave-guiding processes, possibly at the basis of their high photosynthetic efficiency. In this study, we employed a range of imaging, spectroscopic and numerical techniques (including transmission imaging, digital holography, photoluminescence spectroscopy, and numerical simulations based on wide-angle beam propagation method) to identify and describe different mechanisms by which Pleurosigma strigosum frustules can modulate optical radiation of different spectral content. Finally, we correlated the optical response of the frustule to the interaction with light in living, individual cells within their aquatic environment following various irradiation treatments. The obtained results demonstrate the favorable transmission of photosynthetic active radiation inside the cell compared to potentially detrimental ultraviolet radiation.
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| 28. |
- De Tommasi, E., et al.
(författare)
-
Underwater Light Manipulation by the Benthic Diatom Ctenophora pulchella: From PAR Efficient Collection to UVR Screening
- 2021
-
Ingår i: Nanomaterials. - : MDPI AG. - 2079-4991. ; 11:11
-
Tidskriftsartikel (refereegranskat)abstract
- Several species of diatoms, unicellular microalgae which constitute the main component of phytoplankton, are characterized by an impressive photosynthetic efficiency while presenting a noticeable tolerance versus exposure to detrimental UV radiation (UVR). In particular, the growth rate of the araphid diatom Ctenophora pulchella is not significantly affected by harsh treatments with UVR, even in absence of detectable, specific UV-absorbing pigments and even if it is not able to avoid high UV exposure by motility. In this work we applied a multi-disciplinary approach involving numerical computation, photonics, and biological parameters in order to investigate the possible role of the frustule, micro- and nano-patterned silica shell which encloses the cell, in the ability of C. pulchella to efficiently collect photosynthetic active radiation (PAR) and to simultaneously screen the protoplasm from UVR. The characterization of the photonic properties of the frustule has been accompanied by in vivo experiments conducted in water in order to investigate its function as optical coupler between light and plastids.
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| 29. |
- Ever Aguirre, Luis, et al.
(författare)
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Diatom frustules protect DNA from ultraviolet light
- 2018
-
Ingår i: Scientific Reports. - : Springer Science and Business Media LLC. - 2045-2322. ; 8:1
-
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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| 30. |
- Fransson, Agneta, 1964, et al.
(författare)
-
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
-
Ingår i: Annals of Glaciology. - 0260-3055. ; 56:69, s. 245-257
-
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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| 31. |
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| 32. |
- Gastineau, R., et al.
(författare)
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Haslea ostrearia-like Diatoms: Biodiversity out of the Blue
- 2014
-
Ingår i: Advances in Botanical Research. - London : Academic Press Ltd-Elsevier Science Ltd. - 0065-2296. ; 71, s. 441-465
-
Tidskriftsartikel (refereegranskat)abstract
- Diatoms are usually referred to as golden-brown microalgae, due to the colour of their plastids and to their pigment composition, mainly carotenoids (fucoxanthin, diadinoxanthin, diatoxanthin), which mask chlorophylls a and c. The species Haslea ostrearia Gaillon/Bory (Simonsen) appears unique because of its extraplastidial bluish colour, a consequence of the presence of a water-soluble blue pigment at cell apices, marennine. When released in seawater, marenbine can be fixed on gills of oysters and other bivalves, which turn green. This greening phenomenon is economically exploited in Southwestern France, as it gives an added value to oysters. For decades, this singularity ascribed a worldwide distribution to H. ostrearia, first as Vibrio ostrearius, then Navicula ostrearia, last as H. ostrearia, when the genus Haslea was proposed by R. Simonsen (1974). Indeed, this 'birthmark' (presence of blue apices) made H. ostrearia easily recognisable without further scrutiny and identification of the microalga as well as its presence easily deduced from the greening of bivalves. Consequently, the widely admitted cosmopolitan character of H. ostrearia has only been questioned recently, following the discovery in 2008, of a new species of blue diatom in the Black Sea, Haslea karadagensis. The biodiversity of blue diatoms suddenly increased with the finding of other blue species in the Mediterranean Sea, the Canary Islands, etc., the taxonomic characterization of which is in progress. This review thus focuses on the unsuspected biodiversity of blue diatoms within the genus Haslea. Methods for species determination (morphometrics, chemotaxonomy, genomics), as well as a new species, are presented and discussed.
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| 33. |
- Gastineau, R, et al.
(författare)
-
Inheritance of Mitochondrial DNA in the Pennate Diatom Haslea ostrearia (Naviculaceae) during Auxosporulation Suggests a Uniparental Transmission
- 2013
-
Ingår i: Protist. - 1434-4610 .- 1618-0941. ; 164:3, s. 340-351
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Tidskriftsartikel (refereegranskat)abstract
- We present the first study examining mtDNA transmission in diatoms, using sexual progeny of the pennate species Has lea ostrearia (Naviculaceae). A fragment of the cytochrome oxidase subunit I gene (cox1) with 7 nucleic substitutions between parental clones was used as a parental tracer in 16 F1 clones obtained from two pairs of mating crosses. Each cross involved a parental clone isolated from France (Bay of Bourgneuf) and Sweden (Kattegat Bay). We determined that all progeny possessed only one cox1 parental haplotype. These results suggest that the mitochondrial DNA transmission in H. ostrearia is uniparental. Implications and new topics of investigation are discussed. (C) 2013 Elsevier GmbH. All rights reserved.
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| 34. |
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| 35. |
- Granfors, Anna, 1978, et al.
(författare)
-
Biogenic halocarbons in young Arctic sea ice and frost flowers
- 2013
-
Ingår i: Marine Chemistry. - : Elsevier BV. - 0304-4203. ; 155, s. 124-134
-
Tidskriftsartikel (refereegranskat)abstract
- The fate of halocarbons, naturally produced volatile halogenated organic compounds, in young Arctic sea ice was studied to better understand the role of sea ice in halocarbon cycling. In early spring, halocarbons were measured in sea ice frozen in core holes, during 12 days of formation and freezing. In order to understand which factors govern halocarbon concentration and distribution, salinity, temperature and biological parameters were monitored in the growing sea ice. It was found that sea ice participates in the cycling of halocarbons between sea and air. Sea ice concentrations and distributions of these compounds were influenced by production in the ice, where ice-inhabiting microorganisms caused local increases in halocarbon concentrations. Moreover, the halocarbon ice concentration decrease/change with time did not follow ice salinity, suggesting that additional removal processes caused sea ice to be a source of halogens to overlying air. The net production rate of bromoform in the surface of newly frozen ice was estimated to 14 pmol L−1 d−1 and the maximum removal rate was 18 pmol L−1 d−1. In addition frost flowers on newly formed sea ice were identified as contributors of halocarbons to the atmosphere with halocarbon concentrations in the same order of magnitude as in sea ice brine
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| 36. |
- Halbach, Laura, et al.
(författare)
-
Tidewater Glaciers and Bedrock Characteristics Control the Phytoplankton Growth Environment in a Fjord in the Arctic
- 2019
-
Ingår i: Frontiers in Marine Science. - : Frontiers Media SA. - 2296-7745. ; 6
-
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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| 37. |
- 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
-
Ingår i: Frontiers in Marine Science. - : Frontiers Media SA. - 2296-7745. ; 6:October
-
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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| 38. |
- Karlberg, Maria, et al.
(författare)
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Impact of temperature and species interaction on filamentous cyanobacteria may be more important than salinity and increased pCO(2) levels
- 2013
-
Ingår i: Marine Biology. - : Springer Science and Business Media LLC. - 0025-3162 .- 1432-1793. ; 160:8, s. 2063-2072
-
Tidskriftsartikel (refereegranskat)abstract
- A future business-as-usual scenario (A1FI) was tested on two bloom-forming cyanobacteria of the Baltic Proper, Nodularia spumigena and Aphanizomenon sp., growing separately and together. The projected scenario was tested in two laboratory experiments where (a) interactive effects of increased temperature and decreased salinity and (b) interactive effects of increased temperature and elevated levels of pCO(2) were tested. Increased temperature, from 12 to 16 A degrees C, had a positive effect on the biovolume and photosynthetic activity (F (v)/F (m)) of both species. Compared when growing separately, the biovolume of each species was lower when grown together. Decreased salinity, from 7 to 4, and elevated levels of pCO(2), from 380 to 960 ppm, had no effect on the biovolume, but on F (v)/F (m) of N. spumigena with higher F (v)/F (m) in salinity 7. Our results suggest that the projected A1FI scenario might be beneficial for the two species dominating the extensive summer blooms in the Baltic Proper. However, our results further stress the importance of studying interactions between species.
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| 39. |
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| 40. |
- Leu, E., et al.
(författare)
-
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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| 41. |
- Leu, E., et al.
(författare)
-
Effects of changes in ambient PAR and UV radiation on the nutritional quality of an Arctic diatom (Thalassiosira antaretica var. borealis)
- 2006
-
Ingår i: Journal of Experimental Marine Biology and Ecology. - : Elsevier BV. - 0022-0981. ; 337:1, s. 65-81
-
Tidskriftsartikel (refereegranskat)abstract
- Polyunsaturated fatty acids (PUFAs) are essential macromolecules that are synthesized by phytoplankton during spring bloom, and they play a key role in the Arctic food web. They are, however, considered to be sensitive to oxidation by UV radiation (280-400 nm). Changes in the food quality of primary producers may affect the transport of biomass and energy in the whole ecosystem. Using a common Arctic diatom, we looked at the effect of ambient and increased UV radiation on its nutritional quality, specifically, the fatty acid composition and elemental ratios. In May 2004, in the archipelago of Svalbard (79 degrees N), a unialgal culture of Thalassiosira antarctica var. borealis was subjected to a 17-day experiment in outdoor aquaria. The diatoms were kept in semi-continuous culture (40 1) and exposed to three treatments with different levels of UV radiation: none (UV-shielded), ambient, and enhanced. Fatty acid composition, C:N:P ratios, photosynthetic pigment composition, optimum quantum yield of PSII, and cell numbers were analysed over the experimental period. An initial increase in PAR (photosynthetically active radiation, 400-700 nm) intensities profoundly affected the fatty acid composition and substantially inhibited the synthesis of PUFAs, but the relative amounts of PUFAs were not reduced by UV radiation. Enhanced UV radiation did, however, cause a significant reduction in optimum quantum yield of PSII and affected some fatty acids, mainly 18:0 and 16:1 n-7, during the first week of the experiment. Both ambient and enhanced UV radiation caused significantly lower C:P and N:P ratios. At the same time, these treatments elicited a higher relative content of the photoprotective pigments diadinoxanthin and diatoxanthin. After acclimation to the new light levels these effects faded off. Thus, brief periods with high light exposure may cause significant changes in photosynthetic activity and food quality, but the capacity for photo-acclimation seems high. The impact of UV radiation seems to be less important for food quality than that of PAR during a sudden rise in total light intensity. (c) 2006 Elsevier B.V. All rights reserved.
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| 42. |
- Leu, E., et al.
(författare)
-
Fatty acid dynamics during the spring bloom in a High Arctic fjord: importance of abiotic factors versus community changes
- 2006
-
Ingår i: Canadian Journal of Fisheries and Aquatic Sciences. - 0706-652X. ; 63:12, s. 2760-2779
-
Tidskriftsartikel (refereegranskat)abstract
- We followed the fatty acid composition of particulate organic matter (POM) in a High Arctic fjord (79 degrees N; Svalbard, Norway) during and after the spring bloom. The content of essential polyunsaturated fatty acids (PUFAs) was highest (45% of total fatty acids) at the beginning of the bloom, well before the biomass maximum, and decreased linearly towards the end (30%). During the postbloom period, the concentrations of PUFAs remained stable, between 25% and 30%. Redundancy analysis was used to identify the environmental factors that explained the observed variability in the fatty acid composition of phytoplankton. A particular emphasis was put on the potential influence of high irradiances. During the spring bloom, nutrient availability (Si and N), as well as shifts in phytoplankton community composition and chlorophyll a, were shown to account for much of the pattern in fatty acid composition. During the postbloom period, particularly during periods of stratification, light had a pronounced effect on the fatty acid composition. In general, we found a decrease in the relative amount of PUFAs under high light intensities and nutrient limitation.
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| 43. |
- Ligowski, R., et al.
(författare)
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Rhoicosphenia michali: a new species of marine diatom (Bacillariophyta) from King George Island, Antarctica
- 2014
-
Ingår i: Phytotaxa. - : Magnolia Press. - 1179-3155 .- 1179-3163. ; 191:1, s. 141-153
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Tidskriftsartikel (refereegranskat)abstract
- Rhoicosphenia michali sp. nov., described from the shallow sublittoral zone in Antarctica, is the second species in the genus with just one raphe slit on its convex valve. The first species, Rhoicosphenia flexa, was also described from marine coastal habitats in the Southern Hemisphere. Here, the morphology and ecology of R. flexa and R. michali are compared. The new species described herein may be endemic to Antarctica and can be found as free living cells on the shallow seabed, although it mainly occurs on the red alga Georgiella confluens, which is endemic to Antarctica.
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| 44. |
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| 45. |
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| 46. |
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| 47. |
- Mohlin, Malin, 1966, et al.
(författare)
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Interspecific Resource Competition-Combined Effects of Radiation and Nutrient Limitation on Two Diazotrophic Filamentous Cyanobacteria
- 2012
-
Ingår i: Microbial Ecology. - : Springer Science and Business Media LLC. - 0095-3628 .- 1432-184X. ; 63:4, s. 736-750
-
Tidskriftsartikel (refereegranskat)abstract
- The cyanobacterial blooms in the Baltic Sea are dominated by diazotrophic cyanobacteria, the potentially toxic species Aphanizomenon sp. and the toxic species Nodularia spumigena. The seasonal succession with peaks of Aphanizomenon sp., followed by peaks of N. spumigena, has been explained by the species-specific niches of the two species. In a three-factorial outdoor experiment, we tested if nutrient and radiation conditions may impact physiological and biochemical responses of N. spumigena and Aphanizomenon sp. in the presence or absence of the other species. The two nutrient treatments were f/2 medium without NO (3) (-) (-N) and f/2 medium without PO (4) (3-) (-P), and the two ambient radiation treatments were photosynthetic active radiation > 395 nm (PAR) and PAR + UV-A + UV-B > 295 nm. The study showed that Aphanizomenon sp. was not negatively affected by the presence of N. spumigena and that N. spumigena was better adapted to both N and P limitation in interaction with ultraviolet radiation (UVR, 280-400 nm). In the Baltic Sea, these physical conditions are likely to prevail in the surface water during summer. Interestingly, the specific growth rate of N. spumigena was stimulated by the presence of Aphanizomenon sp. We suggest that the seasonal succession, with peaks of Aphanizomenon sp. followed by peaks of N. spumigena, is a result from species-specific preferences of environmental conditions and/or stimulation by Aphanizomenon sp. rather than an allelopathic effect of N. spumigena. The results from our study, together with a predicted stronger stratification due to effects of climate change in the Baltic Sea with increased temperature and increased precipitation and increased UV-B due to ozone losses, reflect a scenario with a continuing future dominance of the toxic N. spumigena.
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| 48. |
- Nilsson, Anders K., 1982, et al.
(författare)
-
Nutraceutical Fatty Acid Production in Marine Microalgae and Cyanobacteria
- 2020
-
Ingår i: Nutraceutical Fatty Acids from Oleaginous Microalgae: A Human Health Perspective. - : Scrivener Publishing LLC. - 9781119631729 ; , s. 23-76
-
Bokkapitel (övrigt vetenskapligt/konstnärligt)abstract
- In light of the potential negative impacts that fisheries and fish aquaculture have on marine ecosystems, alternative sources for long‐chain polyunsaturated fatty acids (LC‐PUFAs) for human consumption are warranted. n‐3 and n‐6 PUFAs have documented beneficial effects on human health and wellbeing. Of particular interest for their nutraceutical properties are the C20 and C22 LC‐PUFAs, represented by arachidonic acid (ARA) of the n‐6 series and eicosapentaenoic‐ and docosahexaenoic acid (EPA and DHA, respectively) of the n‐3 series. LC‐PUFAs can be endogenously synthesized from shorter‐chain precursor molecules by humans. However, this synthesis is limited to why it is often promoted that preformed LC‐PUFAs should be included in the diet, particularly EPA and DHA. Fatty fish and other seafood accumulate n‐3 LC‐PUFAs produced de novo at lower trophic levels, i.e., by marine microalgae and cyanobacteria, and are the main source of dietary EPA and DHA. In this chapter, we review LC‐PUFA biosynthesis pathways and the current use of photosynthetic marine microbes for nutraceutical oil production. Different cultivation techniques, as well as optimal growth conditions, are discussed in the context of future possibilities of exploring microalgae and cyanobacteria for large‐scale LC‐PUFA production.
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| 49. |
- Odmark, S, et al.
(författare)
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Effects of UVB radiation in a microbenthic community of a marine shallow-water sandy sediment
- 1998
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Ingår i: Marine Biology. - 0025-3162. ; 132:2, s. 335-345
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Tidskriftsartikel (refereegranskat)abstract
- The role of ambient and enhanced ultraviolet-B radiation (UVB; 280 to 315 nm) in a natural sand-associated microbenthic community was studied in a 3-week experiment by incubating intact sediment cores from a shallow bay in an outdoor flow-through system with 27 aquaria. After sampling of initial cores, the remaining cores tone per aquarium) were given one of three treatments: no, ambient, and moderately enhanced UVB, and sampled, nine at a time, after 5, 12, and 19 d. The response of the community was studied by analysing algal and meiofaunal composition and biomass, chlorophyll a content, composition of pigments and fatty acids, and content of UV-absorbing compounds (state variables), as well as carbon fixation and allocation, and bacterial productivity (rate variables). Among rate variables, significant effects of UVB-treatments were found for carbon fixation and allocation, while bacterial productivity was not affected. For state variables, a significant response was observed for the composition of microalgae and fatty acids, and for chlorophyll a content. The effect of treatments was mainly observed as differences in development with time (two-way analysis of variance, treatment x time interaction). Towards the end of the experiment, the no-UVB treatment most often differed from one or both of the two treatments with UVB exposure, the latter showing lower values. There were marked successional changes in the community, irrespective of treatment. The microalgal community changed from being dominated by coccoid cyanobacteria and epipsammic diatoms to a dominance of epipelic diatoms and filamentous cyanobacteria. The pattern of carbon allocation, as well as an increased C/N ratio of the sediment, suggested limitation of growth, perhaps by nutrients, at the end of the experiment. This may possibly have acted synergistically with UVB exposure to create the treatment effects. The new knowledge gained from our experiment is that ambient UVB can exert a stress on the function of sand-associated microbenthic communities in shallow waters and that this effect coincides with structural differences in the community.,More experiments in natural or semi-natural systems are needed to allow better prediction of microbenthic community-level responses to UVB.
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- 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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