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Fig. 4. Electron-optical views (a–c) of entire aquatic particles (whole mounts) in surface water collected from Hamilton Harbor and separated into size fractions. (a) An environmental scanning electron microscopy (ESEM) image, which indicates the size and morphology of a typical aggregated particle (a multicomponent floc) from Fraction 3 (F3 of Fig. 1) in topographical view. (b) An ESEM image of a smaller floc from Fraction 4. (c) A high-resolution transmission electron microscopy (TEM) image of a small heterogeneous aggregated particle captured, from raw water, on top of a Formvar film (mounted on a TEM grid). Electron-optical images of ultrathin sections of aggregated particles collected from Hamilton Harbor water fractions (d–f). (d) A TEM image showing individual colloids within a porous large aggregate collected from raw water. (e) A TEM image showing individual colloids in an aggregate collected from Fraction 4 (10- to 20-µm range). (f) A TEM image showing individual colloids in an aggregate collected from Fraction 5 (2- to 10-µm range). The colloidal particles shown in all TEM images (of ultrathin sections above) represent the dominant particles by number. Note that for all three images, the protocol used for fixation and subsequent TEM preparation was the proxy protocol beginning with the step "glutaraldehyde + RR."
