A collection of expert opinions critically evaluates the role of seaweed in blue carbon strategies for climate change mitigation. While the concept of fast-growing seaweed to capture atmospheric carbon is appealing, the experts largely agree that its potential for direct, long-term carbon sequestration is currently overstated and faces significant challenges. One primary limitation is that most farmed seaweed is used for food or other products that quickly decompose, releasing the captured carbon back into the atmosphere. Additionally, only a small fraction of seaweed biomass is sequestered in long-term storage sinks like deep-sea sediments. Furthermore, the process of monitoring, reporting, and verification for seaweed-based carbon dioxide removal is complex and currently lacks accurate tools. More importantly, quantifying the net climate benefit is complicated by life cycle emissions from farming and processing, which can offset carbon gains. Some experts suggest a more viable climate benefit lies in using seaweed to reduce emissions by substituting for products with higher carbon footprints. Socio-economic initiatives like the blue carbon crediting scheme in Japan show a path forward, where credits are purchased to support local communities and conservation, suggesting value beyond pure carbon offsetting. The consensus is that while seaweed farming offers substantial benefits for food security and coastal ecosystems, its most realistic contribution to climate action is through indirect emission reduction, not large-scale carbon removal. A rigorous, science-based approach is essential to avoid hype and ensure sustainable development.
Predator-prey interactions in marine ecosystems are extremely complex, involving a wide variety of species. In contrast, toxin-mediated predator-prey interactions are constrained by species-specific tolerance to the toxin. Tetrodotoxin (TTX), commonly known as pufferfish toxin, is a common factor in such interactions across diverse taxa. It has been recently suggested that TTX-bearing planocerid flatworms contribute to the toxification of other TTX-bearing organisms. However, their contribution to the transfer of TTX in the food web remains unclear. In this study, we investigated the trophic position of the TTX-bearing flatworm Planocera multitentaculata in this transfer using carbon and nitrogen stable isotope analysis. We compared isotope values from wild P. multitentaculata, its putative prey (mollusks such as gastropods and polyplacophorans), and a known predator, the pufferfish Takifugu alboplumbeus. We also reared P. multitentaculata exclusively on the gastropod Monodonta confusa and estimated the trophic enrichment factors for stable isotopes of carbon and nitrogen to be 0.85‰ and 3.28‰, respectively. Based on these findings, the inferred prey of the wild flatworm had stable isotope values similar to those of the gastropod M. confusa and two polyplacophoran species. In contrast, the inferred prey of T. alboplumbeus had significantly different isotope values from P. multitentaculata, supporting the role of flatworms as an intermediate TTX source in marine food webs. These results highlight the importance of planocerid flatworms in TTX transfer and their contribution to toxin accumulation at higher trophic levels.
In conventional incompressible smoothed particle hydrodynamics (ISPH), volume conservation is ensured by maintaining a constant particle number density at each particle. However, in multiphase flow simulations, the presence of different densities can disrupt the compatibility with the continuity equation based on the particle number density. This often leads to numerical instabilities and inaccuracies at the interface. To address this issue, this study proposes a novel, stable multiphase scheme introducing a mathematical construct termed the Interphase Particle (IP). The IP acts as an agent that mediates interparticle forces between different phases. Unlike conventional interpolation-based or over-grid methods, the IP is integrated directly into the Pressure Poisson Equation matrix, allowing the pressure for all phases to be solved simultaneously within a single discretization space. The good performance of the proposed scheme in the energy conservation and reproducibility of interfaces including wall boundaries and numerical stability was validated through several benchmark tests: two-phase hydrostatic fluid columns, an oscillating droplet, the merging of rising bubbles, and a dam break.
The increasing utilization of underground spaces underscores the need for innovative approaches to mitigate stress redistribution and surface irregularities in buried structures. This study examines the mechanisms of stress redistribution and soil arching under diverse trapdoor configurations. These configurations are defined by variations in sample height, boundary conditions, symmetry, yielding width, and static trapdoor portions. The findings revealed that the normalized vertical stresses are highly sensitive to the width of the yielding portion, with larger sample widths intensifying stress redistribution over static trapdoors. A fully developed soil arch, dictated by sufficient sample height and yielding width, eliminates differential surface settlement. Contrary to expectations, the width of the static trapdoors has minimal influence on the arching pattern. Under asymmetrical conditions, the wider side of the yielding zone plays a decisive role in determining the soil cover required to mitigate surface deformations. These results advance understanding of soil-structure interactions, offering critical design insights to enhance the stability and efficiency of buried structures in modern geotechnical engineering.
