Marine Biology (2+1)

Filling up of Utermohl’s simple chambers and Utermohl’s compound chamber

Filling up of Utermohl’s simple chambers

About 100 ml of a water sample collected by Freidinger bottle, Meyer’s bottle or pump is transferred to a suitable sample bottle or flask closed with a ground glass stopper. To this, two or three drops of Lugol’s solution are added. The iodine content of this solution not only fixes and preserves the phytoplanktonic organisms but also makes them cognac coloured. Further, the organisms sink to the bottom as they become heavier absorbing the iodine. Such a treated water sample can be preserved for years if kept tightly closed in darkness.

For filling this chamber, it is placed first over a Petri dish. The flask containing water sample treated with Lugol’s solution is well shaken and the tubular chamber is filled until the water overflows. The chamber is then closed carefully with a cover plate. Care must be taken to see that no air bubbles are trapped inside the chambers. The chamber is then transferred to the Utermohl’s inverted microscope without any agitation and is left undisturbed. The duration needed for the settlement varies with the height of the chamber as the relation of the height to the diameter of the chamber is known to influence the sedimentation. It is also found that if the height exceeds five times the diameter substantial quantities of plankton do not settle at all. It is also experimentally proved that a period of four hours is needed for each centimeter of height for the settlement of the smaller organisms in the chambers of suitable size.

Filling up of Utermohl’s compound chamber

After the setting up the compound chamber in position, the upper tubular chamber is filled with Lugol’s solution-fixed-water sample and the set up is left undisturbed for about 24 hours for proper settling of the plankton in the bottom of shallow chamber. After the sedimentation time, the lower shallow chamber is to be carefully separated. For this, the top tubular portion is carefully slided from the plate chamber in such a way that none of the plankton is stirred up and so lost. To carry out this sliding operation, one places on the right and left of the plat chambers, the plexiglass plates of exactly the same thickness and surface area and one of them is held steady with one hand and with the other hand, the tubular portion is carefully slided together with the coverglass of the plate chamber on to the plate steadily held. The coverglass slides back and accurately closes the plate chamber. The latter is then transferred to the Utermohl’s inverted microscope.