We can't find the internet
Attempting to reconnect
Something went wrong!
Hang in there while we get back on track
Effect of exopolymer gels on the viscoelasticity of mucus-rich saltwater and settling dynamics of particles
AI summary Read the abstract
Researchers investigated how exopolymer gels produced during algal blooms affect the rheological properties of mucus-rich saltwater and the settling dynamics of particles, using xanthan gum as a model exopolymer in sodium chloride solutions. They found that colloidal exopolymers created a stronger internal structure than particulate gels and increased drag coefficients on sinking particles up to sixfold, suggesting colloidal exopolymers retard particle settling in marine environments more effectively.
Algal blooms enrich seawater with gel-like exopolymers modifying the local structure and physio-chemical properties of water column. These effects are particularly intense during mucilage events occurring seasonally in some seas and coastal regions and in thin layers. However, detailed in situ examination is limited, and the effects of biologically modified seawater on microscale processes remain poorly understood. In this study, we experimentally investigated the impact of exopolymer gels on rheological properties of mucus-rich saltwater and consequences on settling dynamics of fast-sinking particles using aqueous solutions of sodium chloride with an addition of xanthan gum, a model exopolymer forming gels dispersed in water. We studied two types of solutions: colloidal dispersion and dispersion with predominant content of particulate gels. The results showed that dispersions consisting of colloidal exopolymers have stronger inner structure than dispersions with predominant particulate exopolymers, suggesting that viscoelastic properties of seawater vary with the structure of gels. Settling velocity and drag exerted on solid spheres and disks were substantially different for the two types of solutions, with the drag coefficient up to six times higher for colloidal than for particulate solutions of corresponding salinity, indicating that colloidal exopolymers may retard particles falling in marine environment more effectively than particulate gels. The findings highlight possible variation in viscoelasticity of mucus-rich saltwater with exopolymer network structure changes in spatial and temporal scales during algal bloom development and implications to the sedimentation of fast-sinking particles such as faecal pellets, carbonate grains, minerals and microplastics.
More Papers Like This
Settling of microplastics in mucus-rich water column: The role of biologically modified rheology of seawater
AI summary Read the abstract
Laboratory experiments showed that naturally occurring exopolymers secreted by marine algae and bacteria convert seawater into a non-Newtonian fluid that slows the sinking of microplastic particles, altering how and where they accumulate in the ocean water column. Understanding these biologically driven settling dynamics is important for predicting microplastic distribution and exposure risk for marine organisms at different depths.
Effects of rheologically stratified seawater during algal bloom on sinking dynamics of microplastics
AI summary Read the abstract
This study investigated how algal blooms affect the sinking behavior of microplastics in seawater by examining the role of exopolymers secreted by microorganisms during bloom events, which make the water more viscous and gel-like. In bloom-affected, rheologically modified seawater, microplastics sank differently than in normal conditions, with some particles being retarded and others accelerated depending on their properties. Understanding these dynamics is important because algal blooms are becoming more frequent globally, and how microplastics sink determines how long they remain in the water column where marine life is exposed to them.
Dataset on sinking of solid particles in non-ionic and single-salt aqueous dispersions of xanthan gum and carrageenan and rheological properties of these dispersions
AI summary Read the abstract
Researchers measured settling dynamics of spheres, disks, and rods in xanthan gum and carrageenan solutions containing individual salts and seawater mixtures, generating a dataset that characterizes how non-Newtonian rheology in marine-like polysaccharide dispersions affects the sinking behavior of small plastic particles.
Viscoelastic and shear-thinning effects of aqueous exopolymer solution on disk and sphere settling
AI summary Read the abstract
Using a gel-like polymer to mimic natural aquatic conditions, researchers found that the gel's non-Newtonian properties significantly slow the settling speed of particles compared to plain water. This suggests microplastics in natural waters rich in organic matter may sink more slowly than lab studies in clean water would predict.
Effects of biologically modified seawater on settling behaviour of microplastics
AI summary Read the abstract
Researchers found that during algal blooms, exopolymers secreted by microorganisms significantly increased seawater viscosity and changed how microplastic particles sank through the water column. This finding means that the sinking behavior of microplastics in real ocean conditions — especially during bloom events — is far more complex than laboratory tests with clean seawater suggest.
Research digests by email
When a large batch of papers lands in the Atlas, we read through it and send a short write-up of what stood out.