New Method for Separation of Skeletal Material from a Plankton Sample

All the most widely known methods described in the literature fall short of these requirements . In the "classical" method described by Be (1969a) and Boltovskoy (1966), the total • sample is inspected through a microscope and any foraminiferal tests visible are removed by a pipette or a brush. The method is time-consuming and inaccurate in that the worker is unconsciously selective towards larger and more conspicuous species such as the red Globigerinoides rubev or Hastigerina pelagiaa. Another source of biased error is the element of fatigue, which causes a decrease in operator accuracy through the working period. In the floatation method proposed by Be (1959b), a saturated NaCl solution is used to separate shelled from soft-bodied plankton. When placed in this solution in a settling tube, ideally the soft-bodied plankton remain floating while foraminifera, with the other shelled organisms, sink to the bottom. A major draw-back of this method is that spinose species are commonly entangled with the other soft-bodied plankton and remain floating. By the ignition method, proposed by Sachs et_ al^ (1964) samples are initially treated with hydrogen peroxide. After the excessive soft organic material is digested, the samples are ignited in a muffle furnace at 500°C. This treatment removes all organic material, leaving only skeletal matter. Both the initial treatment with the digestive and the final treatment in the furnace attacks the calcareous material to some extent. For example, the surfaces of the tests of foraminifera and pteropods is etched and most of the spines are removed in this process. In many instances it was found that samples had exploded in the furnace causing loss and contamination of the sample.