101 research outputs found
Inter- and intra-specific carbon and nitrogen assimilation by dinoflagellate and diatom species
Phytoplankton are key components in primary production and their growth is determined mainly by the availability of nitrogen-nutrients in the ocean. The paradigm that phytoplankton prefer ammonium over nitrate when both substrates are present has been tested using 15N-labelled tracers on cultured diatoms and dinoflagellates isolated from two widespread geographical areas – the Baltic Sea and the Arabian Sea.
We found contrary to the paradigm that both taxa
preferred nitrate over ammonium and a significant within-species variation in N assimilation. Carbon uptake rates in the same experiments were estimated using 13C-labelled tracer
Young L2-learners' meaning-making in engaging in computer-assisted language learning
[EN] This study explores how newly arrived young students created meaning, communicated, and expressed themselves using digital technology in the subject of Swedish as a second language (SSL). The qualitative case study presented in this article focuses on how the orchestration of teaching contributed to opportunities for digital meaning-making in the SSL subject in four classrooms at three schools in a city in Sweden. The notion of language as being fluid, which involves a critical approach to languages as separable entities, considers linguistic and embodied meaning-making, including digital technology, in social processes. This approach recognizes the roles of technology and digital meaning-making in young students’ second language acquisition. Moreover, technological innovations facilitate immediate and accessible communication. In today’s language studies, ethnicity only is not considered an adequate focus of analysis. Furthermore, the meaning-making practices of newly arrived primary school-aged students remain under-investigated. In the present study, data collected in classroom observations and teacher interviews revealed three themes regarding the students’ utilization of digital technology to develop their multilingual skills. One insight was that the newly arrived students used digital technology strategically when they engaged in meaning-making activities with peers and teachers. When the students took the initiative in computer-assisted language learning, they displayed agency in meaning-making by being their own architects. The findings of this research provided insights into how the orchestration of teaching in Swedish as a second language to newly arrived students affects their opportunities to use multilingualism in meaning-making while employing digital technology.Hell, A.; Godhe, A.; WennÃ¥s Brante, E. (2021). 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Time capsules in natural sediment archives—Tracking phytoplankton population genetic diversity and adaptation over multidecadal timescales in the face of environmental change
Digital Literacies or Digital Competence: Conceptualizations in Nordic Curricula
This article examines how the concepts of digital literacies and digital competence are conceptualized in curricula for compulsory education within the Nordic countries. In 2006, the European Union defined digital competence as one of eight key competences for lifelong learning. The terms digital literacies and digital competence have since been used interchangeably, particularly in policy documents concerning education and the digitalization of educational systems and teaching. However, whether these concepts carry similar meanings, and are understood in a similar way, across languages and cultures is not self-evident. By taking the curricula in Sweden, Denmark, Finland, and Norway as examples, this article attempts to clarify similarities and differences in how the concepts are interpreted, as well as what implications this has for the digitalization of education. The analyses reveal that different terms are used in the curricula in the different countries, which are connected to themes or interdisciplinary issues to be incorporated into school subjects. The conceptualizations of the terms share a common emphasis on societal issues and a critical approach, highlighting a particular Nordic interpretation of digital literacies and digital competence
Priority effects in a planktonic bloom-forming marine diatom
Priority effects occur when a species or genotype with earlier arrival has an advantage such that its relative abundance in the community or population is increased compared with later-arriving species. Few studies have dealt with this concept in the context of within-species competition. Skeletonema marinoi is a marine diatom that shows a high degree of genetic differentiation between populations over small geographical distances. To test whether historical events such as priority effects may have been important in inducing these patterns of population differentiation, we performed microcosm experiments with successive inoculation of different S. marinoi strains. Our results show that even in the absence of a numerical advantage, significant priority effects were evident. We propose that priority effects may be an important mechanism in initiating population genetic differentiation
Growth of a common planktonic diatom quantified using solid medium culturing
The ability to grow on solid culture medium is a pre-requisite for a successful microbial genetic model organism. Skeletonema marinoi, a bloom-forming, planktonic marine microalga, is widely used in ecological, evolutionary and population genetics studies. We have tested and confirmed the ability of this common organism to grow on solid culture medium (agar) under experimentally manipulated conditions. We established a protocol for quantifying growth characteristics - length of lag phase, growth rate, maximum biomass yield - on agar medium. The procedure was tested under experimental treatments and the resulting growth changes correlated with those observed in standard liquid culture. The ability to grow on solid medium broadens the use of S. marinoi as a molecular model, where agar is routinely used for various purposes (growth, selection, storage); and the possibility to quantify colony growth opens the way for high throughput, automated, or semi-automated phenotyping solutions
Exploring the impact of multi-decadal environmental changes on the population genetic structure of a marine primary producer
Dead or alive: sediment DNA archives as tools for tracking aquatic evolution and adaptation
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 new methods, coupled with independent evidence of biotic and abiotic forcing factors, can provide a holistic view of past ecosystems beyond that offered by standard palaeoecology, help us assess implications of ecological and molecular change for contemporary ecosystem functioning and services, and improve our ability to predict adaptation to environmental stress
Toxic Algae Silence Physiological Responses to Multiple Climate Drivers in a Tropical Marine Food Chain
Research on the effects of climate change in the marine environment continues to accelerate, yet we know little about the effects of multiple climate drivers in more complex, ecologically relevant settings – especially in sub-tropical and tropical systems. In marine ecosystems, climate change (warming and freshening from land run-off) will increase water column stratification which is favorable for toxin producing dinoflagellates. This can increase the prevalence of toxic microalgal species, leading to bioaccumulation of toxins by filter feeders, such as bivalves, with resultant negative impacts on physiological performance. In this study we manipulated multiple climate drivers (warming, freshening, and acidification), and the availability of toxic microalgae, to determine their impact on the physiological health, and toxin load of the tropical filter-feeding clam, Meretrix meretrix. Using a structural equation modeling (SEM) approach, we found that exposure to projected marine climates resulted in direct negative effects on metabolic and immunological function and, that these effects were often more pronounced in clams exposed to multiple, rather than single climate drivers. Furthermore, our study showed that these physiological responses were modified by indirect effects mediated through the food chain. Specifically, we found that when bivalves were fed with a toxin-producing dinoflagellate (Alexandrium minutum) the physiological responses, and toxin load changed differently and in a non-predictable way compared to clams exposed to projected marine climates only. Specifically, oxygen consumption data revealed that these clams did not respond physiologically to climate warming or the combined effects of warming, freshening and acidification. Our results highlight the importance of quantifying both direct and, indirect food chain effects of climate drivers on a key tropical food species, and have important implications for shellfish production and food safety in tropical regions.</p
New Approach Using the Real-Time PCR Method for Estimation of the Toxic Marine Dinoflagellate Ostreopsis cf. ovata in Marine Environment
Background: We describe the development and validation of a new quantitative real time PCR (qrt-PCR) method for the
enumeration of the toxic benthic dinoflagellate Ostreopsis cf. ovata in marine environment. The benthic Ostreopsis sp. has a
world-wide distribution and is associated during high biomass proliferation with the production of potent palytoxin-like
compounds affecting human health and environment. Species-specific identification, which is relevant for the complex of
different toxins production, by traditional methods of microscopy is difficult due to the high morphological variability, and
thus different morphotypes can be easily misinterpreted.
Methodology/Findings: The method is based on the SYBR I Green real-time PCR technology and combines the use of a
plasmid standard curve with a ‘‘gold standard’’ created with pooled crude extracts from environmental samples collected
during a bloom event of Ostreopsis cf. ovata in the Mediterranean Sea. Based on their similar PCR efficiencies (95% and 98%,
respectively), the exact rDNA copy number per cell was obtained in cultured and environmental samples. Cell lysates were
used as the templates to obtain total recovery of DNA. The analytical sensitivity of the PCR was set at two rDNA copy
number and 8.061024 cell per reaction for plasmid and gold standards, respectively; the sensitivity of the assay was of cells
g21 fw or 121 in macrophyte and seawater samples, respectively. The reproducibility was determined on the total linear
quantification range of both curves confirming the accuracy of the technical set-up in the complete ranges of quantification
over time.
Conclusions/Significance: We developed a qrt-PCR assay specific, robust and high sample throughput for the absolute
quantification of the toxic dinoflagellate Ostreopsis cf. ovata in the environmental samples. This molecular approach may be
considered alternative to traditional microscopy and applied for the monitoring of benthic toxic microalgal species in the
marine ecosystems
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