1,720,963 research outputs found
Decomposition of organic matter produced by the macroalgae Ulva compressa: A study on blue carbon potential
No full textGlobal warming is a present issue, impacting the marine environment by increasing temperatures. Higher temperatures create conditions suitable for algae-blooms, increasing biomass of Ulva compressa. This project aims to investigate the decomposition of organic matter produced by the macroalgae U. compressa through two different experiments. The expectation is that under higher temperatures and oxic conditions, the decomposition of the organic matter produced by U. compressa will be faster. This study aims to investigate the blue carbon potential of U. compressa with two different experiments; one on the decomposition of biomass and the other one on the decomposition of released DOC. The experiments ran over a period of 63 to 70 days, investigating the impacts of two factors; temperature at 15°C and 25°C and oxygen availability, with anoxic and oxic conditions. The results of this study showed that temperature and oxygen had an impact on the decomposition of organic matter of U. compressa. The decomposition of biomass was higher under high temperature with oxygen compared to lower temperatures without oxygen. The DOC released by U. compressa did show a trend of slowing decomposition rates over time under 15 °C. This study concludes that the experiments with oxygen had a higher decomposition rate of organic matter than those without, and the decomposition of biomass was faster at 25°C
Physiological response of Fucus vesiculosus and Gracilaria vermiculophylla under Ocean Warming and Acidification
No full textThe Baltic Sea is considered to be a representative preview of future coastal oceanic conditions altered by climate change, such as increasing ocean warming and and acidification (Reusch et al., 2018b). This study examines the physiological response to these stressors of two macroalgae species: Fucus vesiculosus, a foundational species in the Baltic sea, and the invasive species Gracilaria vermiculophylla.Samples of the two macroalgae species, collected from the coastline of Isefjord in Denmark, underwent a set of four different treatments in a 2x2 factorial experiment imitating future oceanic conditions - increased temperature and decreased pH. Relative growth rate, photosynthetic rate and survivorship were examined. The results provided evidence of physiological stress in the form of necrosis and tissue deterioration for both algae. Similarly, a negative effect on relative growth atincreased temperature was observed for both species (F. vesiculosus: −71.0 ± 24.6%, G. vermiculophylla: −18.4 ± 36.8%), while nevertheless boosting the photosynthetic rate compared to the control treatment (F. vesiculosus: 18.6 ± 2.9%, G. vermiculphylla: 26.6 ± 29.6%). Under increased CO2 concentration, G. vermiculophylla experienced a high increase in photosynthetic rate, lending support to the hypothesis that G. vermiculophylla will have a competitive advantage under future climatic conditions. However, an increased photosynthetic rate was also documented for F. vesiculosus, albeit smaller. Under the most ecologically realistic treatment, where both stressors act together, the two stressors interacted synergistically on the photosynthesis of both algae, producing an impact above the theoretical additive impact. Conversely, the combined treatment acted antagonistically on the relative growth rate of both macroalgae. However, these trends were not found to be statistically significant. Nonetheless, G. vermiculophylla still appeared to have an overall higher tolerance and a positive response during theexperiment in terms of growth and photosynthetic rate.In conclusion, the results indicate a slight competitive advantage for G. vermiculophylla over thenative species F. vesiculosus under ocean acidification and ocean warming in hard-bottom coastal waters. Thus, G. vermiculophylla is likely to pose a threat of ecological succession to F. vesiculosus, the current foundation species
Adaptation of Littorina littorea for grazing on Gracilaria vermiculophylla
No full textThis paper aims to test adaptation of the gastropod L. littorea ability to graze on the invasive macro algae G. vermiculophylla when it is introduced to its environment. This is achieved by grazing experiments where gastropods from different areas of Denmark are given G. vermiculophylla and the native macro algae F. vesiculosus. The locations from which L. littorea are sampled is chosen based on presence of G. vermiculophylla such that gastropods that have been in the presence of the invasive species can be compared to those that have not. L. littorea seems to be able to graze on both algae with the same preference for both the selected populations. The gastropod shows no signs of adaptation when introduced to G. vermiculophylla as the population not introduced to the invasive macro algae seems to have a higher grazing rate on G. vermiculophylla than the population previously introduced to the algae. The grazing rates show high variance which may hide potential grazing preferences of L. littorea. To get better results a higher grazer biomass than the one used is recommended.<br/
Investigating Seaweed-derived DOC - Decomposition Rates and Chemical Composition of DOC from Three Brown Algae Species in the Context of Blue Carbon Potential
No full textDeveloping sustainable seaweed aquaculture of the native kelp Ecklonia radiata in New Zealand
Full text linkThe native kelp Ecklonia radiata is a target species for seaweed aquaculture in New Zealand because of its broad distribution and desirable biomass profile (e.g., alginate, fucoidan, and phlorotannins). However, commercial farming practices for E. radiata are not yet developed. The objective of this thesis was therefore to create foundations for sustainable seaweed aquaculture of E. radiata in New Zealand by filling key knowledge gaps regarding patterns of genetic structure (Chapter 2), spatial and temporal variation in biomass composition (Chapter 3), the development of high-throughput methods for biomass grading (Chapter 4), and marine farm design (Chapter 5).
The development of specialised cultivars is central for optimising key commercial traits for seaweed aquaculture; however, the introduction of genotypes from significantly different genetic sub-populations can reduce genetic diversity and genetic structure of wild populations. Analysis of molecular variance in populations of E. radiata in the North Island of New Zealand revealed significant differences at all three hierarchical levels of genetic structure that were analysed. The highest regional differentiation occurred between Wellington and other regions and was supported by Bayesian and redundancy models showing a high degree of genetic clustering among regions. Furthermore, pairwise Fₛₜ (genetic differentiation) revealed significant differences between most sites showing strong genetic structure and low connectivity also at a local level. These findings indicate that cultivars of E. radiata should not be translocated outside their area of origin, to prevent introducing genotypes from significantly different genetic sub-populations to wild sub-populations.
Most analysed biomass components of E. radiata showed high spatial variation between sites, including alginate, glucose, and phlorotannins. However, there was no clear pattern in biomass composition among regions, indicating that these differences in biomass content are unlikely to be caused by genetic differences (i.e., Wellington samples did not stand out). Conversely, a strong seasonal pattern was detected with significant temporal variation detected for half of the quantified components. These results indicate that environmental variation is a key driver for the biomass composition of E. radiata and that the high spatial variation was due to do site-specific environmental conditions. In general, the biomass composition of E. radiata was comparable to that of commercially grown northern hemisphere species and could be a suitable southern hemisphere alternative for a wide range of commercial applications.
The large spatial and temporal variation in biomass composition creates a need for high-throughput grading of raw biomass. Highly accurate models were built for estimating biomass concentration of glucose, alginate, phlorotannins, and carbon using mid-infrared (MIR) and near-infrared (NIR) spectroscopy. NIR models generally demonstrated higher accuracy and lower sensitivity to outliers than MIR models. Furthermore, samples from the Wellington region could consistently be identified based on the NIR data, demonstrating strong phenotypic differences between regions. These results show that NIR and MIR are valuable tools for high-throughput grading of raw seaweed biomass samples and can be used to establish provenance.
Finally, farming trials quantified the effect of vertical and horizontal line configurations and farming depth on survival and growth of E. radiata at a commercial New Zealand green-lipped mussel (Perna canaliculus) marine farm. Only seaweed growing on vertical lines survived four months after deployment, and juvenile growth by elongation and maximum average individual weight was markedly higher on vertical lines compared to horizontal lines. Survival rates on vertical lines decreased at shallow depths, likely influenced by a combination of light and temperature stress. Similarly, the overall high mortality observed during the experiment was likely correlated to the prolonged marine heatwave of the summer of 2021/22 at the farm location. Conclusively, these results support vertical lines rather than horizontal line for farming of E. radiata.
In summary, this thesis has significant scientific implications for regulatory (i.e., cultivar translocation), commercial (i.e., harvesting timing, biomass grading, and source tracing), and practical farming aspects (i.e., line configuration and a first proof on concept) of aquaculture of E. radiata in New Zealand and provides directions for future research and development
Effects of simulated heat wave scenarios on; growth, mortality, photosynthesis, pigment content and oxidative stress in Danish Saccharina latissima (Laminariales, Phaeophyceae)
No full textKelps are important foundation species in coastal cold-water ecosystems, and loss of these organisms are a threat to global biodiversity. The kelp Saccharina latissima is widely abundant on the northern hemisphere, however severe reduction in the abundance of the kelp has been observed in Northern Europe during recent decades. S. latissima is adapted to cold waters and the decline of the kelp is likely caused by increased frequency and intensity of extreme summer heat events as a result of climate change. We assessed the physiological stress response of S. latissima when exposed to 4 simulated heat wave scenarios of maximum 15°C, 18°C, 21°C and 24°C. Mortality was only significant for S. latissima exposed to the 24°C heat wave where >90% died after 8 days of exposure to maximum temperature. Furthermore, growth rate and photosynthetic efficiency decreased significantly, while production of reactive oxygen species (ROS) increased significantly for S. latissima exposed to 21°C and 24°C compared to 15°C. Our results indicate that the reduced photosynthetic efficiency at high temperatures may partly have been caused by photoinhibition of PSII and low chlorophyll a content due to photooxidation. The concentration of carotenoid pigments increased at high temperatures which was likely an antioxidant response to thermal increased production of ROS. Contrary to our expectations yield of regulated heat dissipation (ΦNPQ) decreased with increasing temperatures indication a lack of photoprotective capacity during heat stress. Our findings indicate that thermal stress caused by extreme events, like the 21˚C and 24˚C heat waves pose a serious threat to Danish populations of S. latissima.Kelps are important foundation species in coastal cold-water ecosystems, and loss of these organisms are a threat to global biodiversity. The kelp Saccharina latissima is widely abundant on the northern hemisphere, however severe reduction in the abundance of the kelp has been observed in Northern Europe during recent decades. S. latissima is adapted to cold waters and the decline of the kelp is likely caused by increased frequency and intensity of extreme summer heat events as a result of climate change. We assessed the physiological stress response of S. latissima when exposed to 4 simulated heat wave scenarios of maximum 15°C, 18°C, 21°C and 24°C. Mortality was only significant for S. latissima exposed to the 24°C heat wave where >90% died after 8 days of exposure to maximum temperature. Furthermore, growth rate and photosynthetic efficiency decreased significantly, while production of reactive oxygen species (ROS) increased significantly for S. latissima exposed to 21°C and 24°C compared to 15°C. Our results indicate that the reduced photosynthetic efficiency at high temperatures may partly have been caused by photoinhibition of PSII and low chlorophyll a content due to photooxidation. The concentration of carotenoid pigments increased at high temperatures which was likely an antioxidant response to thermal increased production of ROS. Contrary to our expectations yield of regulated heat dissipation (ΦNPQ) decreased with increasing temperatures indication a lack of photoprotective capacity during heat stress. Our findings indicate that thermal stress caused by extreme events, like the 21˚C and 24˚C heat waves pose a serious threat to Danish populations of S. latissima
Substitution of DEHP as Softtener in Medical Equipment
No full textIn this study the issue of phthalate softeners in medical equipment was examined. Phthalates, including di(2-ethylhexyl) phthalate (DEHP), have long been suspected for being carcinogenic or toxic for reproduction. Based on the latter DEHP in 2008 entered REACH’s authorization list with accompanying prohibition of industrial use from July 2015. Medical devices are, however, excluded from REACH, wherefore patients continue to be exposed to DEHP during treatment. The aim of the study is, to analyze which factors are decisive for the substitution of DEHP as a softener in medical devices, by applying Geels' (2004) theory of change in sociotechnical systems. Based on interviews with the medico producer Coloplast, the Hospital of Glostrup and the organization The Ecological Council, as well as through literature, the problem was scrutinized. It was found that risk assessments are not capable of determine a definitive risk evaluation of DEHP, because different players do not agree upon analysis of the underlying data. It was also found that while the European law left little possibility for a stricter regulation because of lobbyism from the industry, the Danish government has several indirect and direct possibilities for strengthening the substitution of DEHP in medical devices. Lastly it was found that for a large part of the medical devises, alternative phthalate-free alternatives are available which can be used without compromising patient safety or the economy of the user. Insufficient political action to ensure market pull or law incentive was concluded as the decisive factor holding back the substituting of DEHP in medical devises.In this study the issue of phthalate softeners in medical equipment was examined. Phthalates, including di(2-ethylhexyl) phthalate (DEHP), have long been suspected for being carcinogenic or toxic for reproduction. Based on the latter DEHP in 2008 entered REACH’s authorization list with accompanying prohibition of industrial use from July 2015. Medical devices are, however, excluded from REACH, wherefore patients continue to be exposed to DEHP during treatment. The aim of the study is, to analyze which factors are decisive for the substitution of DEHP as a softener in medical devices, by applying Geels' (2004) theory of change in sociotechnical systems. Based on interviews with the medico producer Coloplast, the Hospital of Glostrup and the organization The Ecological Council, as well as through literature, the problem was scrutinized. It was found that risk assessments are not capable of determine a definitive risk evaluation of DEHP, because different players do not agree upon analysis of the underlying data. It was also found that while the European law left little possibility for a stricter regulation because of lobbyism from the industry, the Danish government has several indirect and direct possibilities for strengthening the substitution of DEHP in medical devices. Lastly it was found that for a large part of the medical devises, alternative phthalate-free alternatives are available which can be used without compromising patient safety or the economy of the user. Insufficient political action to ensure market pull or law incentive was concluded as the decisive factor holding back the substituting of DEHP in medical devises
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
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