ALBERT

Description: Gas hydrates dissociation could induce or trigger submarine landslides, especially in upper continental slopes where hydrates are vulnerable to natural and artificial perturbations. This work investigates destabilization mechanisms of an upper continental slope undergoing hydrate dissociation and identifies spatiotemporal failure modes influenced by characteristics of the overburden above the hydrate-bearing layer (i.e. the hydrate reservoir). A Thermo-Hydro-Chemical coupled numerical model of transient pore pressure induced by hydrate dissociation is coupled with the limit equilibrium slope analysis method to study the spatiotemporal evolution of the potential sliding plane and to calculate the corresponding factor of safety. The results suggest that overpressure generated by the liberated fluid from hydrate dissociation is the primary reason for instability in a gentle marine slope. The study identifies three sliding modes, namely co-melting non-interface sliding, co-melting interface sliding, and post-melting non-interface sliding, depending on the overburden's characteristics, including overburden thickness, permeability, and cohesion. Co-melting non-interface sliding takes place during hydrate dissociation if the hydrate reservoir underlies a thin, pervious and low-cohesion overburden cover. For less permeable and more cohesive overburdens, the potential sliding plane is deeper and co-melting interface sliding could be triggered due to overpressure developed at the reservoir-overburden interface. If the hydrate reservoir is covered by a thick, low-permeability and slightly cohesive overburden, post-melting non-interface sliding could occur after the hydrates are completely dissociated. This failure is delayed, because the gas/water trapped at the interface during hydrate dissociation is insufficient to trigger instability due to very high overburden stresses. However, as the gas migrates upwards over time and encounters a weak zone in the overburden deposits, failure could happen within the overburden deposits even after hydrate dissociation stops. The findings help to improve our fundamental understanding about the destabilization mechanism and failure modes of the continental slopes undergoing hydrate dissociation, and to delineate the vulnerable configurations of the slopes.

Description: n our daily lives, we consume foods that have been transported, stored, prepared, cooked, or otherwise processed by ourselves or others. Food storage and preparation have drastic effects on the chemical composition of foods. Untargeted mass spectrometry analysis of food samples has the potential to increase our chemical understanding of these processes by detecting a broad spectrum of chemicals. We performed a time-based analysis of the chemical changes in foods during common preparations, such as fermentation, brewing, and ripening, using untargeted mass spectrometry and molecular networking. The data analysis workflow presented implements an approach to study changes in food chemistry that can reveal global alterations in chemical profiles, identify changes in abundance, as well as identify specific chemicals and their transformation products. The data generated in this study are publicly available, enabling the replication and re-analysis of these data in isolation, and serve as a baseline dataset for future investigations.

Description: A comparison of gouge and hammer coring techniques in intertidal wetland soils highlights a significant effect of soil compaction of up to 28% associated with the widely applied hammer coring method employed in Blue Carbon research. Hammer coring reduces the thickness of the soil profile and increases the dry bulk density, which results in an overestimation of the soil OC stock of up to 22%. In saltmarshes with multiple different soil units, we show that hammer coring is unsuitable for the calculation of OC stocks and should be avoided in favour of Russian or gouge cores. Compaction changes both soil dry bulk density and porosity and we show that resultant radiometric chronologies are compromised, almost doubling mass accumulation rates. While we show that the OC (%) content of these sediments is largely unchanged by coring method, the implication for OC burial rates are profound because of the significant effect of hammer coring on the calculation of soil mass accumlation rates.

Description: Seagrasses provide multiple ‘ecosystem services' in coastal waters, including carbon sequestration. However, this ‘Blue Carbon’ potential has been only evaluated for certain species from some areas of the world. In this study, we provide initial estimates on the magnitude and local variability of carbon sequestration, as organic carbon stocks, for seagrass meadows of Cymodocea nodosa (Ucria) Ascherson in the oceanic island of Gran Canaria (Canary Islands, Spain, central-eastern Atlantic). Six seagrass meadows were selected; at each meadow, cores inserted up to 30 cm in the seabed were collected in the ‘interior’, ‘edge’ and ‘unvegetated’ bottoms immediately adjacent to seagrass patches. We estimated organic carbon (Corg) pools by means of the Loss of Ignition (LOI) procedure. Overall, larger Corg pools were observed in the ‘interior’ and 'edges' of meadow patches than in adjacent ‘unvegetated’ bottoms. At the meadow-level, Corg pools were not predicted neither by the meadow area, nor by the mean shoot density, or sediment grain fractions. Overall, the total estimated stock was 86.20 ± 19.06 Mg C ha−1. By considering the total potential extension of seagrass meadows across the entire island perimeter, we estimated a total stock of 60.34 Gg of C, for a mean estimated financial value of 919,432.249 € (1313.47 € ha−1), which ranges between 351,631.35 € (502.33 € ha−1) and 1,498,954.45 € (2141.36 € ha−1), according to varying market prices in the last 5 years. This work highlights, therefore, the importance of meadows underpinned by C. nodosa not only at an ecological, but also at an economic level, in particular from the perspective of regional climate change adaptation strategies.

Description: Ciona intestinalis is within the group of taxa that are spreading globally and is one of the most thriving invasive marine species, known to depress both species richness and abundance at a local scale in distinct geographic areas. It is a dominant biofouling agent, associated with the decreasing economic incomes from aquaculture operations around the world. Ciona intestinalis was first observed in 2007 at Straumsvík in Southwest Iceland. The present study was designed to provide general information on its current distribution across Icelandic harbours. The species was found only on the SW coast of Iceland, in dense aggregations reaching up to 876 ind/m2 in all harbours from Grindavík to Akranes. The current work provides information that can be used to track the dispersal of C. intestinalis populations along the Icelandic coast and for the development of effective management decisions.

Description: Interest in microalgae-derived products is growing, mostly due to their unique characteristics and range of industrial applications. To obtain different products, one must employ specific pretreatments that retain the properties of the biologically active compounds extracted from microalgae biomass; thus, new extraction techniques require frequent upgrades. Due to increased interest in economically viable and ecologically friendly processes, new extraction methods that can be incorporated into microalgae biorefinery systems have become the main focus of research. Therefore, this review aims to address the potential applications, future prospects, and economic scenario of the new physicochemical treatments used in the extraction of bioactive microalgae compounds.

Description: Long-chain polyunsaturated fatty acids (LC-PUFAs) especially ω-3 fatty acids provide significant health benefits for human beings. However, ω-3 LC-PUFAs cannot be synthesized de novo in mammals. Traditionally, ω-3 LC-PUFAs are extracted from marine fish, and their production depends on sea fishing, which has not met ever-increasing global demand. To address the challenges, innovative cellular engineering strategies need to be developed. In nature, many fungi and microalgae are rich in ω-3 LC-PUFAs, representing promising sources of ω-3 LC-PUFAs. The latest progress in developing new cellular engineering strategies toward sustainable ω-3 LC-PUFAs production using fungi and microalga has demonstrated that they can to some extent address the supply shortage. In this review, we critically summarize the recent progress in enhancing the productivity in various ω-3 LC-PUFAs-producing organisms, as well as the latest efforts of biosynthesizing PUFAs in heterogenous biosystems. In addition, we also provide future perspectives in developing genetic toolkits for LC-PUFAs producing microbes so that cut-edging biotechnology such as gene stacking and genome editing can be further applied to increase the productivity of ω-3 LC-PUFAs.

Description: Factors affecting carotenoid extraction with edible oils were examined using edible brown seaweed, Sargassum horneri, as main sample. The results indicate that drying was essential to extract fucoxanthin (Fx) from S. horneri and physical (boiling) and chemical (acid/alkali) pretreatment of the wet sample increased the extraction rate of Fx. Additionally, more Fx was found from the dried S. horneri powder with a smaller particle size. The extraction rate of Fx is affected by the extraction temperature and time, showing that the effective extraction would be obtained at 50 °C within 12 hr extraction. Among the oils used, short-chain (C4 and C6) triacylglycerol (TAG) (SCT) and medium-chain (C8) TAG (MCT) could extract more Fx from S. horneri and more β-carotene and lutein from spinach and olive leaves. The relatively lower viscosity of SCT and MCT would be the most likely reason for the higher extraction rates of both TAGs.

Description: Sargassum fusiforme polysaccharides, acidic water-soluble polysaccharides extract from Sargassum fusiforme, are mainly composed of alginic acid, fucoidan and laminaran. Alginic acid is carboxyl-containing polysaccharide formed by joining β-D-mannuronic acid and α-L-guluronic acid through β-(1→4)/α-(1→4) glycosidic bond. Fucoidan, a natural water-soluble sulfated heteropolysaccharide with fucose and sulfuric acid groups as the core structure, is mainly linked by L-fucose through α-(1→3) glycosidic bond and has the strongest biological activity. Laminaran is mainly composed of β-D-glucose through β-(1→3) glycosidic bond linkage. Sargassum fusiforme polysaccharides have a variety of pharmacological activities, including antioxidant, anti-tumor, promoting immunity, anti-aging, prompting bone growth, lowering blood glucose, anti-coagulation, anti-virus, anti-bacteria, anti-fatigue, promoting growth and development, and skin protection. These activities are closely related to the functions of fucoidan in Sargassum fusiforme polysaccharides, which fucoidan is able to strengthen immune system and antioxidation in human body. In this review, the composition, the isolation and purification, and the biological activities of Sargassum fusiforme polysaccharides are discussed and can bereference for further study.

Description: Numerical simulation is important for practical and efficient assessment of hydrate reservoir formation stability and gas production potential. The history-matching simulation of hydrate gas production tests is complex due to coupled THM (thermo-hydro-mechanical) phenomena. The well log data from the Eastern Nankai Trough methane gas production site suggest vertically heterogeneous field properties. In the previous numerical simulation research of this site, the heterogeneous geological data were homogenized by adopting the standard mean-field theory, which can potentially lead to inaccurate simulation results due to the mesh size effect. By introducing new upscaling techniques for the permeability profiles and mechanical responses, a revised homogenization approach is proposed to improve the coupled THM simulation accuracy. In this study, seven gas production simulations of a hypothetical reservoir, six simulations of the Eastern Nankai Trough gas production test, and four simulations of the randomly generated site formation production test with different mesh sizes and different homogenization approaches were carried out to demonstrate that the proposed upscaling techniques can improve the accuracy of the simulation results with a coarse mesh model. This work, in turn, provides researchers and field engineers a much quicker way to assess the complex geomechanical behaviors of hydrate gas production site.