Marianne Ellegaard

Marianne Ellegaard
University of Copenhagen · Department of Plant and Environmental Science

About

96
Publications
28,767
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2,941
Citations
Citations since 2016
30 Research Items
1789 Citations
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2016201720182019202020212022050100150200250300
2016201720182019202020212022050100150200250300
2016201720182019202020212022050100150200250300

Publications

Publications (96)
Article
Full-text available
In this paper we conceptualize formative peer feedback principles by analyzing and comparing six empirical examples of formative peer feedback in a set of international STEM (science, technology, engineering, and mathematics) contexts. By discussing how these different approaches to peer feedback unfold in practice, we aim to facilitate the bridgin...
Article
Full-text available
Polysaccharides constitute an important carbon pool in marine systems, but much is still unknown about the fate and degradation of these compounds. They are derived partly from production in situ, and in coastal areas, they are partly terrestrially derived, originating from freshwater runoff from land. The aim of this study was to test the applicab...
Chapter
The diatoms, a unique class of microalgae, are enclosed in an extracellular, silica-based porous structure called the frustule. The frustule is denser than water and reduces cell buoyancy, thus increasing the risk of sinking out of the sunlight illuminated zone. Yet, diatoms are an outstanding ecological group with respect to global abundance, spec...
Article
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DNA can be preserved in marine and freshwater sediments both in bulk sediment and in intact, viable resting stages. Here, we assess the potential for combined use of ancient, environmental, DNA and timeseries of resurrected long-term dormant organisms, to reconstruct trophic interactions and evolutionary adaptation to changing environments. These n...
Article
Denne artikel beskriver baggrunden for et pilotprojekt med formativ peer feedback på et karaktergivende essay på et stort obligatorisk bachelorkursus. Peer feedback blev implementeret hovedsageligt som svaret på et behov hos de studerende for mere feedback. Vi diskuterer teorien bag peer feedback som metode i undervisningen og udmøntningen af proje...
Article
Full-text available
Dinoflagellates encompass two taxonomic systems (dual taxonomy) reflected by separate traditions of nomenclature: one based mainly on living motile stages, and the other mainly on fossil cysts (dual nomenclature). Modern cysts may therefore bear two names if their life cycle is known. There have been attempts to rationalize this duality, but at spe...
Article
Diatoms are phototrophic single-celled microalgae encased in a cell wall (frustule) made of amorphous silicate. The frustule comprises two valves connected by a variable number of girdle bands, all exhibiting periodic micro/ nanoporous structures. We studied the optical properties in water of girdle bands from the centric diatom Coscinodiscus grani...
Article
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We present a summary of two round-table discussions held during two subsequent workshops in Montreal (Canada) on 16 April 2014 and Ostend (Belgium) on 8 July 2015. Five species of the genus Achomosphaera Evitt 1963 and 33 of the genus Spiniferites Mantell 1850 emend. Sarjeant 1970 occuring in Pliocene to modern sediments are listed and briefly desc...
Article
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The biomarker IP 25 and fossil diatom assemblages preserved in seafloor sediments are commonly used as proxies for paleo Arctic sea-ice reconstructions, but how their production varies over the seasons and is exported to the sediment remains unclear. We analyzed IP 25 concentrations and diatom assemblages from a 5-week consecutive series of sea-ice...
Article
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The biomarker IP25 and fossil diatom assemblages preserved in seafloor sediments are commonly used as proxies for paleo Arctic sea-ice reconstructions, but how their production varies over the seasons and is exported to the sediment remains unclear. We analyzed IP25 concentrations and diatom assemblages from a 5-week consecutive series of sea-ice c...
Article
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The intricate patterning of diatom silica frustules at nanometer-to-micrometer scales makes them of interest for a wide range of industrial applications. For some of these applications, a specific size range in nanostructure is required and may be achieved by selecting species with the desired properties. However, as all biological materials, diato...
Article
Optical properties of diatom silicate frustules inspire photonics and nanotechnology research. Whether light interaction with the nano-structuring of the frustule also affects diatom photosynthesis has remained unclear due to lack of information on frustule optical properties under more natural conditions. Here we demonstrate that the optical pro...
Article
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In the past decade, research on long-term persistence of phytoplankton resting stages has intensified. Simultaneously, insight into life-cycle variability in the diverse groups of phytoplankton has also increased. Aquatic 'seed banks' have tremendous significance and show many interesting parallels to terrestrial seed beds of vascular plants, but a...
Article
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Diatoms are in focus as biological materials for a range of photonic applications. Many of these applications would require embedding a multitude of diatoms in a matrix (e.g. paint, crème or lacquer); however, most studies on the photonic and spectral properties of diatoms frustules (silica walls) have been carried out on single cells. In this stud...
Article
Owing to the dynamic nature of nutrient-phytoplankton interactions, ambient macronutrient concentrations reveal little about the impact of nutrient availability on phytoplankton biomass and community composition at any given point in time or space. Here, however, we examine a global dataset (n = 262) where phytoplankton community structure and biom...
Article
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Undisturbed records of resting stages produced in the past and stored in coastal sediments are very valuable to science, because they may provide unique insights into past evolutionary and ecological trajectories. Within marine phytoplankton, multi-decadal time series of monoclonal strains germinated from resting stages have been established for di...
Article
Significant changes in frustule morphology of Coscinodiscus granii induced by different light regimes have previously been observed, but whether these changes are companied by similar changes in cellular silicon concentration or are solely due to reorganization is unknown. The influence of six different light regimes, blue (B), green (G), yellow (Y...
Article
Strains of a dinoflagellate from the Salton Sea, previously identified as Protoceratium reticulatum and yessotoxin producing, have been reexamined morphologically and genetically and Pentaplacodinium saltonense n. gen. et sp. is erected to accommodate this species. Pentaplacodinium saltonense differs from Protoceratium reticulatum (Claparède et Lac...
Article
Formative feedback currently receives attention as an effective means of increasing student learning. However, how to frame feedback to achieve the best effect is an ongoing debate. In this study we analyse a written data-set of 174 segments of teacher feedback and student response, coded using 10 emergent feedback and 14 response categories. As it...
Article
Full-text available
The effect on diatom frustule morphology of long-term cultivation at mono-spectral light (six wavelengths combined with two light intensities) was investigated. The results showed that the size of Coscinodiscus granii frustules and the foramen size increased after 10-month cultivation for all light treatments, compared to results after short-term c...
Article
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Many marine protists form resting stages that can remain viable in coastal sediments for several decades. Their long-term survival offers the possibility to explore the impact of changes in environmental conditions on population dynamics over multidec-adal time scales. Resting stages of the phototrophic dinoflagellate Pentapharsodinium dalei were i...
Chapter
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Dinoflagellates are important components of marine plankton as both primary producers and predators on bacteria and microeukaryotes. About 200 species, most of these estuarine, form a resting stage, called a cyst, as part of their life-cycle. Dinoflagellate cysts are mostly organic, composed of a very resistant material called dinosporin, and are o...
Chapter
The past of the Baltic Sea has been intensively investigated using a wealth of techniques. By far the largest number of studies has focused on sea level and salinity changes, driven by global climate and isostatic crustal rebound after the Baltic Sea emerged underneath the Weichselian Ice Sheet ca. 15,000 cal. years BP. The post-glacial history of...
Article
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Diatoms are ubiquitous organisms in aquatic environments and are estimated to be responsible for 20–25 % of the total global primary production. A unique feature of diatoms is the silica wall, called the frustule. The frustule is characterized by species-specific intricate nanopatterning in the same size range as wavelengths of visible and ultravio...
Article
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Mean body size decreases with increasing temperature in a variety of organisms. This size–temperature relationship has generally been tested through space but rarely through time. We analyzed the sedimentary archive of dinoflagellate cysts in a sediment record taken from the West Greenland shelf and show that mean cell size decreased at both intra-...
Article
Resting stages of marine phytoplankton have been shown to have potential for long-term survival and to remain viable in marine sediments for up to about a century. This study documents for the first time long-term survival in haptophytes and prasinophytes, by germination of resting stages of Isochrysis galbana and Mantoniella squamata from up to 40...
Article
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We present the first multi-site study of dinoflagellate cyst records spanning ca. AD 1860–2000 from the west Iberian coast. Our aim was to reconstruct environmental changes in the Western Iberia Upwelling Ecosystem, one of the most biologically productive areas in the world, and an active fishery region. A major shift in cyst assemblages was record...
Article
Full-text available
Diatoms are unicellular algae enclosed in intricate bio-silicified walls with repetitive nanostructures in a size range which makes them potentially relevant for a broad spectrum of industrial applications. How to optimize the nano-scale structures of the frustule for utilization of diatoms in nanotechnology is one of the technological challenges f...
Article
We report experimental and theoretical verification of the nature and position of multiple interference points of visible light transmitted through the valve of the centric diatom species Coscinodiscus granii. Furthermore, by coupling the transmitted light into an optical fiber and moving the diatom valve between constructive and destructive interf...
Article
Protoperidinium species with two anterior intercalary plates were originally classified by Jörgensen in the subgenus Archaeperidinium and assigned to the sections Excentrica, Avellana and Archaeperidinium by Taylor, on the basis of the relative size of anterior intercalary plates and the extent of cingulum displacement. Phylogenetic relationships a...
Article
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Round spiny brown cysts with apiculocavate processes were isolated from sediments of Lake Saroma, Japan, Changle Harbor, East China Sea, China, Jinzhou Harbor, Bohai Sea, China, and San Pedro Harbor, California, USA. Superficially similar round spiny brown cysts of the species, Oblea acanthocysta were, for comparison, restudied through light micros...
Article
Corrigendum Corrigendum to ''Taxonomic re-examination of the toxic armoured dinoflagellate Pyrodinium bahamense Plate 1906: Can morphology or LSU sequencing separate P. bahamense var. compressum from var.
Article
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Pyrodinium bahamense Plate 1906 is a tropical to subtropical dinoflagellate that can cause paralytic shellfish poisoning (PSP). Based on differences in the morphology of the motile stage, as well as geographic distribution, this species was separated into two varieties, the toxic var. compressum and the non-toxic var. bahamense by Steidinger et al....
Article
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Gymnodinium fissum was described by Levander (1894) from the Baltic Sea near Helsinki, and we argue, based on morphological and molecular studies of material from the type locality, and on cultures from the Åland islands, Puerto Rico, Portugal and USA identified as Gyrodinium instriatum, Gymnodinium instriatum, Gyrodinium uncatenum and Gyrodinium s...
Article
Dated sediment cores taken near the head and mouth of a tropical estuary, Nha-Phu/Binh Cang, in south central Viet Nam were analyzed for changes over time in physical, chemical and biological proxies potentially influenced by removal of the mangrove forest lining the estuary. A time-series of satellite images was obtained, which showed that the dep...
Article
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In this study, a global data set on size-fractionated chlorophyll distributions collected in the open ocean (depth > 400 m) is used to investigate phytoplankton community size structure in relation to temperature and inorganic nutrient availability in an attempt to identify the individual and shared effects of these 2 factors. The macroecological p...
Data
A new toxin-producing marine diatom, Nitzschia bizertensis sp. nov., isolated from the Bizerte Lagoon (Tunisia, Southwest Mediterranean Sea) is, based on studies on eight different strains, characterized morphologically by light microscopy, transmission and scanning electron microscopy, and phylogeneti- cally using the nuclear rDNA regions: SSU, IT...
Chapter
Within dinoflagellate research the fields of geology and biology come together in studies of the resting stage, the cyst. Studies of this stage and life-cycle transitions can tie together the geological fossil record of dinoflagellates and the ecology of living dinoflagellates. This review focuses on possible new research areas within ploidy shifts...
Article
Changes in total abundance and in species composition of phytoplankton in the last 150 years in the southern Black Sea were investigated through a paleoecological study of two sediment cores. The results show changes in the species composition and a marked increase in total abundance of siliceous protists after around 1960. In core 22 (42°13.534′ N...
Article
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Effective population size (Ne) determines the rate of genetic drift and the relative influence of selection over random genetic changes. While free-living protist populations characteristically consist of huge numbers of cells (N), the absence of any estimates of contemporary Ne raises the question whether protist effective population sizes are com...
Article
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Marine protist species have been used for several decades as environmental indicators under the assumption that their ecological requirements have remained more or less stable through time. However, a growing body of evidence suggests that marine protists, including several phytoplankton species, are in fact highly diverse and may quickly respond t...
Data
Upper pH tolerance limits for growth for the 18 Pentapharsodinium dalei strains at salinity 15 and 30. (DOCX)
Article
Full-text available
Pentapharsodinium dalei is a widely distributed cold-water dinoflagellate, which is used in palaeoecology as an indicator of relatively warmer conditions in polar and sub-polar regions. This species has been proposed to be one of the first indicators of global warming at high latitudes. We devel-oped the first microsatellite markers for P. dalei to...
Article
In this paper we describe a new species, Archaeperidinium saanichi sp. nov. within the Archaeperidinium minutum Jörgensen 1912 species complex. We examined the morphological variation of the cyst and motile stage by incubation experiments from sediment samples collected in coastal British Columbia (Canada), and compared it to closely related specie...
Article
Full-text available
The phytoplankton species Gymnodinium catenatum is responsible for major worldwide losses in aquaculture due to shellfish toxicity. On the West coast of the Iberian Peninsula, toxic blooms have been reported since the mid-1970s. While the recent geographical spread of this species into Australasia has been attributed to human-mediated introduction,...
Article
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Ribeiro, S., Moros, M., Ellegaard, M. & Kuijpers, A. 2012 (January): Climate variability in West Greenland during the past 1500 years: evidence from a high-resolution marine palynological record from Disko Bay. Boreas, Vol. 41, pp. 68–83. 10.1111/j.1502-3885.2011.00216.x. ISSN 0300-9483. Here we document late-Holocene climate variability in West Gr...
Article
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We report on the survival and germination of up to a century-old marine protist resting stages naturally preserved in sediments from Koljö Fjord on the west coast of Sweden. This work has focused on germination of dinoflagellate cysts, but diatom resting stages were also observed. We record the longest known survival of dormant dinoflagellate cells...
Article
Full-text available
Photosynthesis evolved in the oceans more than 3 billion years ago and has persisted throughout all major extinction events in Earth's history. The most recent of such events is linked to an abrupt collapse of primary production due to darkness following the Chicxulub asteroid impact 65.5 million years ago. Coastal phytoplankton groups (particularl...
Article
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This paper presents research on the genetic structure and diversity of populations of a common marine protist and their changes over time. The bloom-forming diatom Skeletonema marinoi was used as a model organism. Strains were revived from anoxic discrete layers of a (210)Pb-dated sediment core accumulated over more than 100 y, corresponding to >40...
Article
We present a detailed record of shifts in species composition of the toxic diatom genus Pseudo-nitzschia from 1905 to 2001 in Mariager Fjord, Denmark, most probably driven by changes in nitrogen loading to the coastal environment and increasing temperatures in the sea. The fertile Mariager Fjord is a long narrow sill-fjord with a permanently anoxic...
Article
Full-text available
Mertens, K. N., Dale, B., Ellegaard, M., Jansson, I.-M., Godhe, A., Kremp, A. & Louwye, S. 2010: Process length variation in cysts of the dinoflagellate Protoceratium reticulatum, from surface sediments of the Baltic–Kattegat–Skagerrak estuarine system: a regional salinity proxy. Boreas, 10.1111/j.1502-3885.2010.00193.x. ISSN 0300-9483. Results are...
Poster
Scandinavian sill fjords, such as Koljö Fjord in Sweden, are unique environments with limited oxygen supply, minimum tidal activity, continuous accumulation of fine sediment and virtually no bioturbation. This allows for the formation and preservation of laminated sediments which are a natural archive with great potential for temporal studies. Dino...