Ultrastructure of marine snow. I. Transmission electron microscopy methodology

Four different approaches to determine the ultrastructure of amorphous aggregates and their principal components are evaluated for their ability to resolve structural components as small as 1 nm. Based on extensive comparative analysis, the advantages and major drawbacks of the different methods are discussed. Based on experience with marine snow from the Adriatic Sea, it is concluded that only a combination of fixation and preservation treatments ensures optimal interpretation of the results. Specific emphasis is placed on the use of a hydrophilic resin (Nanoplast®) which allows fixation of highly hydrated polysaccharide fibrils in their original configuration and subsequent visualization on a nm scale.