|De scheiding van slib en plankton|
Budding, M.C. (1974). De scheiding van slib en plankton. NIOZ-rapport, 1974(4). Nederlands Instituut voor Onderzoek der Zee: Texel. 38 pp.
Deel van: NIOZ-rapport. Netherlands Institute for Sea Research (NIOZ): Den Burg. ISSN 0923-3210, meer
It is possible to separate non-living suspended matter and living plankton with the help of a common laboratory centrifuge and a commercial silica-gel called LUDOX. With this method it becomes possible to determine particle size of suspended matter and plankton separately with e.g. a Coulter Counter. The following method has been used. First the particle size distribution of the original (mixed) sample is determined with the Coulter Counter. Then an aliquot is centrifuged in order to concentrate the particles in a smaller volume. Then the concentrated sample is brought into a centrifuge phial that contains a 22% sucrose-solution on top of a layer of LUDOX. The sample is centrifuged during ten minutes with a velocity of 3500 rpm. After this, the non-living particles are concentrated on the bottom of the phial whereas the plankton is concentrated on top of the LUDOX. The plankton is carefully collected and resuspended in (filtered) seawater. Counting this plankton in the Coulter Counter gives the size distribution as it was in the original sample. The size distribution of non-living particles concentrated on the bottom of the phial will in most cases not give the original size distribution: complex processes of flocculation and aggregation of clay particles and organic matter probably will take place during concentration and centrifuging, making it necessary to use an indirect method.