| 1. |
- Majaneva, Markus, et al.
(författare)
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Sea-ice eukaryotes of the Gulf of Finland, Baltic Sea, and evidence for herbivory on weakly shade-adapted ice algae
- 2017
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Ingår i: European Journal of Protistology. - : Elsevier. - 0932-4739 .- 1618-0429. ; 57, s. 1-15
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Tidskriftsartikel (refereegranskat)abstract
- To determine community composition and physiological status of early spring sea-ice organisms, we collected sea-ice, slush and under-ice water samples from the Baltic Sea. We combined light microscopy, HPLC pigment analysis and pyrosequencing, and related the biomass and physiological status of sea-ice algae with the protistan community composition in a new way in the area. In terms of biomass, centric diatoms including a distinct Melosira arctica bloom in the upper intermediate section of the fast ice, dinoflagellates, euglenoids and the cyanobacterium Aphanizomenon sp. predominated in the sea-ice sections and unidentified flagellates in the slush. Based on pigment analyses, the ice-algal communities showed no adjusted photosynthetic pigment pools throughout the sea ice, and the bottom-ice communities were not shade-adapted. The sea ice included more characteristic phototrophic taxa (49%) than did slush (18%) and under-ice water (37%). Cercozoans and ciliates were the richest taxon groups, and the differences among the communities arose mainly from the various phagotrophic protistan taxa inhabiting the communities. The presence of pheophytin a coincided with an elevated ciliate biomass and read abundance in the drift ice and with a high Eurytemora affinis read abundance in the pack ice, indicating that ciliates and Eurytemora affinis were grazing on algae. (C) 2016 Elsevier GmbH. All rights reserved.
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| 2. |
- Majaneva, Sanna, et al.
(författare)
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Deficiency syndromes in top predators associated with large-scale changes in the Baltic Sea ecosystem
- 2020
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Ingår i: PLOS ONE. - : Public Library of Science. - 1932-6203. ; 15:1
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Tidskriftsartikel (refereegranskat)abstract
- Vitamin B1 (thiamin) deficiency is an issue periodically affecting a wide range of taxa worldwide. In aquatic pelagic systems, thiamin is mainly produced by bacteria and phytoplankton and is transferred to fish and birds via zooplankton, but there is no general consensus on when or why this transfer is disrupted. We focus on the occurrence in salmon (Salmo salar) of a thiamin deficiency syndrome (M74), the incidence of which is highly correlated among populations derived from different spawning rivers. Here, we show that M74 in salmon is associated with certain large-scale abiotic changes in the main common feeding area of salmon in the southern Baltic Sea. Years with high M74 incidence were characterized by stagnant periods with relatively low salinity and phosphate and silicate concentrations but high total nitrogen. Consequently, there were major changes in phytoplankton and zooplankton, with, e.g., increased abundances of Cryptophyceae, Dinophyceae, Diatomophyceae and Euglenophyceae and Acartia spp. during high M74 incidence years. The prey fish communities also had increased stocks of both herring and sprat in these years. Overall, this suggests important changes in the entire food web structure and nutritional pathways in the common feeding period during high M74 incidence years. Previous research has emphasized the importance of the abundance of planktivorous fish for the occurrence of M74. By using this 27-year time series, we expand this analysis to the entire ecosystem and discuss potential mechanisms inducing thiamin deficiency in salmon.
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| 3. |
- Fridolfsson, Emil, et al.
(författare)
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Limited effects of macro-nutrient ratios on thiamin content and transfer in phytoplankton and copepods
- 2023
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Ingår i: Journal of Plankton Research. - : Oxford University Press. - 0142-7873 .- 1464-3774. ; 45:2, s. 360-371
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Tidskriftsartikel (refereegranskat)abstract
- Vitamin B-1 (thiamin) is primarily produced by bacteria, phytoplankton and fungi in aquatic food webs and transferred to higher trophic levels by ingestion. However, much remains unknown regarding the dynamics this water-soluble, essential micronutrient; e.g. how it relates to macronutrients (carbon, nitrogen and phosphorous). Nutrient limitation has been found to be related to periods of thiamin deficiency as well as in models. Hence, thiamin transfer to copepods from three phytoplankton species from different taxa was investigated, along with the effect of various nutrient regimes on thiamin content. Nutrient levels did not affect thiamin content of phytoplankton nor the transfer to copepods. Instead, phytoplankton displayed species-specific thiamin and macronutrient contents and whilst a higher thiamin content in the prey lead to higher levels in copepods, the transfer was lower for Skeletonema compared to Dunaliella and Rhodomonas. In all, thiamin transfer to copepods is not only dependent on thiamin content of the prey, but also the edibility and/or digestibility is of importance. Thiamin is essential for all organisms, and this study offers insights into the limited effect of macronutrients on the dynamics and transfer of thiamin in the aquatic food webs.
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| 4. |
- Fridolfsson, Emil, et al.
(författare)
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Seasonal variation and species-specific concentrations of the essential vitamin B₁ (thiamin) in zooplankton and seston
- 2019
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Ingår i: Marine Biology. - New York, NY : Springer. - 0025-3162 .- 1432-1793. ; 166:6, s. 1-13
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Tidskriftsartikel (refereegranskat)abstract
- Thiamin (vitamin B1) is mainly produced by bacteria and phytoplankton and then transferred to zooplankton and higher trophic levels but knowledge on the dynamics of these processes in aquatic ecosystems is lacking. Hence, the seasonal variation in thiamin content was assessed in field samples of copepods and in pico-, nano- and micro-plankton of two size classes (0.7–3 µm and > 3 µm) collected monthly in the Baltic Sea during 3 years and in the Skagerrak during 1 year. Copepods exhibited species-specific concentrations of thiamin and Acartia sp. had the highest carbon-specific thiamin content, at both locations. Even members of the same genus, but from different systems contained different levels of thiamin, with higher thiamin content per specimen in copepods from the Skagerrak compared to congeners from the Baltic Sea. Furthermore, our results show that the small plankton (0.7–3 µm) had a higher carbon-specific thiamin content compared to the large (> 3 µm). Additionally, there was a large seasonal variation and thiamin content was highly correlated comparing the two size fractions. Finally, there was an overall positive correlation between thiamin content in copepods and plankton. However, for periods of high thiamin content in the two size fractions, this correlation was negative. This suggests a decoupling between thiamin availability in pico-, nano- and micro-plankton and zooplankton in the Baltic Sea. Knowledge about concentrations of this essential micronutrient in the aquatic food web is limited and this study constitutes a foundation for further understanding the dynamics of thiamin in aquatic environments.
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| 5. |
- Granhag, Lena, 1974, et al.
(författare)
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First recordings of the ctenophore Euplokamis sp. (Ctenophora, Cydippida) in Swedish coastal waters and molecular identification of this genus
- 2012
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Ingår i: Aquatic Invasions. - : Regional Euro-Asian Biological Invasions Centre Oy (REABIC). - 1818-5487 .- 1798-6540. ; 7:4, s. 455-463
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Tidskriftsartikel (refereegranskat)abstract
- The ctenophore Euplokamis sp. was observed and collected in the Gullmar fjord on the west coast of Sweden in April-August 2011 during regular jellyfish and zooplankton monitoring. In April-May 2011, both larval and adult Euplokamis sp. were collected in the surface water of the fjord and in June-August in the deep part of the fjord at 110-100 m. The typical morphological and behavioral characters of Euplokamis sp. were observed (i.e. coiled tentacle side branches and rapid swimming both in forward and reverse). With no published sequence data from the ctenophore family Euplokamidae, molecular identification using the nuclear 18S rRNA gene and internal transcribed spacer region I region (ITS1) revealed that Euplokamis sp. individuals were closely related to the morphologically similar ctenophore family Mertensiidae. Therefore, morphological and molecular data support the identification as Euplokamis. Euplokamis sp. densities in the deep water of the Gullmar fjord in June 2011 reached similar densities as the local ctenophore Beroe spp. The presence of Euplokamis sp. and other ctenophores in the area is discussed together with the importance of continuous monitoring of gelatinous forms to include detection of less frequent and more fragile ctenophore species. We also discuss the importance of molecular identification for ctenophore larvae and adult ctenophores of small size.
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| 6. |
- Lehtiniemi, Maiju, et al.
(författare)
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Distribution and reproduction of the Arctic ctenophore Mertensia ovum in the Baltic Sea
- 2013
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Ingår i: Marine Ecology Progress Series. - : Inter-Research Science Center. - 0171-8630 .- 1616-1599. ; 491, s. 111-124
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Tidskriftsartikel (refereegranskat)abstract
- Species identification based on morphological characteristics has caused misidentifications and led to twisted views of abundances and roles of ctenophores. Based on extensive field studies from 2007 to 2010, the occurrence of the arctic ctenophore Mertensia ovum was genetically verified in the southern, central and northern Baltic Sea, and its egg production, distribution and abundance were studied in relation to physical factors. Genetic analyses indicate that M. ovum is by far the most abundant small ctenophore in the Baltic Sea. Specimens from a 20 yr old ctenophore collection were also genetically identified as M. ovum, contrary to their previous morphological identification as another ctenophore species, Pleurobrachia pileus. Thus, earlier reports on P. pileus in the Baltic Sea may actually refer to M. ovum. The abundance of M. ovum was regulated by both salinity and temperature, with highest abundances found in sea areas and water layers at temperatures <7 degrees C, salinities >5.5 and oxygen levels >4 ml l(-1). During summer, the highest abundances of ctenophores and their eggs were found near the halocline, while the distribution was more uniform throughout the water column during winter. Only ctenophores >3.5 mm (oral-aboral length) produced eggs in the experiments, with an average rate of 2.2 eggs ind.(-1) d(-1). Finally, comparison with published data from the 1980s (assuming that those data refer to M. ovum) indicates that the present-day ctenophore abundance is similar to 80% lower in the north and similar to 55% higher in the southern parts of the Baltic Sea, due to reasons yet to be established.
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| 7. |
- Majaneva, Sanna, et al.
(författare)
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Feeding of the Arctic ctenophore Mertensia ovum in the Baltic Sea : evidence of the use of microbial prey
- 2014
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Ingår i: Journal of Plankton Research. - : Oxford University Press (OUP). - 0142-7873 .- 1464-3774. ; 36:1, s. 91-103
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Tidskriftsartikel (refereegranskat)abstract
- Since its first reported appearance in the Baltic Sea in 2007, there has been a little research on the role of the Arctic ctenophore Mertensia ovum in this ecosystem. We provide results from the first feeding experiments of M. ovum from the northern Baltic Sea. Experiments were conducted with various prey types; picocyanobacteria Synechococcus bacillaris, ciliates Mesodinium rubrum, nauplii of mixed copepod species and copepodites of Eurytemora affinis. Molecular gut content analyses were also used to measure in situ feeding of M. ovum on the picocyanobacteria. The observed clearance rates on M. rubrum (< 9.0 mL predator(-1) h(-1)), and S. bacillaris (<7.5 mL predator(-1) h(-1)) were lower than those reported for similar-sized ctenophore species feeding on similar prey. Similarly, clearance rates of M. ovum on copepodites and copepod nauplii were close to zero, implying significantly lower predation on crustacean prey compared with other ctenophores. Overall, M. ovum predation rates were relatively low with a maximum daily consumption of 0.95 mu g C ind.(-1) day(-1) (similar to 15.8% of estimated predator carbon content). In addition, we examined the vertical distribution of M. ovum in relation to that of micro- and mesozooplankton and found greater overlap with potential microplankton prey than with mesozooplankton. Taken together, these results imply that in the Baltic Sea, M. ovum feed mainly on bacterio-and microplankton, thus potentially contributing to the coupling between the microbial loop and higher consumers in the pelagic food web.
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| 8. |
- Majaneva, Sanna, et al.
(författare)
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Where are they now? : - A case study of the impact of international travel support for early career Arctic researchers
- 2016
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Ingår i: Polar Science. - : Elsevier BV. - 1873-9652 .- 1876-4428. ; 10:3, s. 382-394
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Tidskriftsartikel (refereegranskat)abstract
- Supporting and training the next generation of researchers is crucial to continuous knowledge and leadership in Arctic research. An increasing number of Arctic organizations have developed initiatives to provide travel support for Early Career Researchers (ECRs) to participate in workshops, conferences and meetings and to network with internationally renowned scientific leaders. However, there has been little evaluation of the effectiveness of these initiatives. As a contribution to the 3rd International Conference on Arctic Research Planning, a study was conducted to analyze the career paths of ECRs who received travel funding from the International Arctic Science Committee between the start of the International Polar Year (2007-2008) and 2013. Two surveys were used: one sent to ECRs who received IASC travel support and one as a specific event study to those unsuccessfully applied for IASC travel support to the IPY 2010 Conference. The results of the surveys indicate that travel support was beneficial to both the research and careers of the respondents, especially if the ECR was engaged with a task or responsibility at the event. Survey responses also included suggestions on how funds could be better used to support the next generation of Arctic researchers. (C) 2016 The Authors. Published by Elsevier B.V.
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| 9. |
- Roslin, Tomas, et al.
(författare)
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The use of DNA barcodes in food web construction - terrestrial and aquatic ecologists unite!
- 2016
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Ingår i: Genome. - : Canadian Science Publishing. - 0831-2796 .- 1480-3321. ; 59:9, s. 603-628
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Tidskriftsartikel (refereegranskat)abstract
- By depicting who eats whom, food webs offer descriptions of how groupings in nature (typically species or populations) are linked to each other. For asking questions on how food webs are built and work, we need descriptions of food webs at different levels of resolution. DNA techniques provide opportunities for highly resolved webs. In this paper, we offer an expose of how DNA-based techniques, and DNA barcodes in particular, have recently been used to construct food web structure in both terrestrial and aquatic systems. We highlight how such techniques can be applied to simultaneously improve the taxonomic resolution of the nodes of the web (i.e., the species), and the links between them (i.e., who eats whom). We end by proposing how DNA barcodes and DNA information may allow new approaches to the construction of larger interaction webs, and overcome some hurdles to achieving adequate sample size. Most importantly, we propose that the joint adoption and development of these techniques may serve to unite approaches to food web studies in aquatic and terrestrial systems-revealing the extent to which food webs in these environments are structured similarly to or differently from each other, and how they are linked by dispersal.
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| 10. |
- Werner, Kirstin, et al.
(författare)
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Arctic in Rapid Transition : Priorities for the future of marine and coastal research in the Arctic
- 2016
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Ingår i: Polar Science. - : Elsevier BV. - 1873-9652 .- 1876-4428. ; 10:3, s. 364-373
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Tidskriftsartikel (refereegranskat)abstract
- Understanding and responding to the rapidly occurring environmental changes in the Arctic over the past few decades require new approaches in science. This includes improved collaborations within the scientific community but also enhanced dialogue between scientists and societal stakeholders, especially with Arctic communities. As a contribution to the Third International Conference on Arctic Research Planning (ICARPIII), the Arctic in Rapid Transition (ART) network held an international workshop in France, in October 2014, in order to discuss high-priority requirements for future Arctic marine and coastal research from an early-career scientists (ECS) perspective. The discussion encompassed a variety of research fields, including topics of oceanographic conditions, sea-ice monitoring, marine biodiversity, land-ocean interactions, and geological reconstructions, as well as law and governance issues. Participants of the workshop strongly agreed on the need to enhance interdisciplinarity in order to collect comprehensive knowledge about the modern and past Arctic Ocean's geo-ecological dynamics. Such knowledge enables improved predictions of Arctic developments and provides the basis for elaborate decision-making on future actions under plausible environmental and climate scenarios in the high northern latitudes. Priority research sheets resulting from the workshop's discussions were distributed during the ICARPIII meetings in April 2015 in Japan, and are publicly available online. (C) 2016 Elsevier B.V. and NIPR. All rights reserved.
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