Marine Biology (2+1)

CENTRIFUGATION

In this method, 10-20 ml of the water sample is centrifuged for about 15-30 minutes at 1500-2000 rpm with the help of an electrical centrifuge. The supernatant water is removed until the volume is reduced to 1/10-1/30 of the initial. The plankton is resuspended in the remaining volume of the water and the suspension is either precipitated by adding a few drops of 1% potassium aluminium sulphate or fixed with weak neutralized formalin or Lugol’s solution. Subsequently, it is examined and counted in a Kolkwitz’s chamber or a Sedgwick rafter counting cell.