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Marine Colloids


  1. Peter H. Santschi

Published Online: 15 JUL 2005

DOI: 10.1002/047147844X.oc1702

Water Encyclopedia

Water Encyclopedia

How to Cite

Santschi, P. H. 2005. Marine Colloids. Water Encyclopedia. 4:27–32.

Author Information

  1. Texas A&M University, Galveston, Texas

Publication History

  1. Published Online: 15 JUL 2005


Aquatic colloids, nanoparticles and macromolecules in the 1 nm to 1 µm size range, are characterized by large interfacial energies and scatter light. Colloids are most often separated from seawater through ultrafiltration. They are characterized by physical techniques, such as diffusion, permeation, or light scattering, and can be imaged by atomic force and electron microscopy. Chemically, they are composed mostly of organic macromolecules, which make up 20–30% of marine dissolved organic carbon (DOC). Marine colloidal organic matter (COM) contains biologically resistant heteropolycondensations, such as humic-type molecules (geopolymers), and products of carbon fixation and consumption such as exopolymeric substances (EPS) excreted by microorganisms. Both geopolymers and biopolymers are amphiphilic with charged and uncharged groups, and contain strong metal-binding ligands, rendering them metal- and radionuclide sequestering agents. Therefore, colloids in the ocean can act as vectors of metal and radionuclide removal and of solubilization, depending on the biomolecule, as well as modifiers of metal bioavailability in delicately balanced marine ecosystems. In addition, marine colloids are also important in their response to global change, as they enhance the sinking flux of carbon, and thus, play a role in global carbon cycling.


  • colloids;
  • nanoparticles;
  • macromolecules;
  • marine environment;
  • seawater;
  • exopolymeric substances (EPS);
  • acid polysaccharides (APS);
  • transparent exopolymeric particles (TEP);
  • fibrils;
  • polysaccharides;
  • amphiphiles;
  • metal complexation;
  • ultrafiltration