Continuous Oxygen Recording in Seawater

Abstract

Summary of the results and experiences obtained during the work with the oxygen recorder.

The apparaus is very simple to build and use, and it works rapidly. It is possible by means of this apparature to take continuous readings of the variations of oxygen content in the water downward from the surface. The readings give a picture which is available immediately, and which may be useful for the marine biologist working at sea. For hydrographic work it may be of interest that the recorder indicates the depths where the oxygen content changes rapidly, which may be important in deciding where to take additional observations. With a few determinations of the oxygen content by the usual method it is possible to obtain a linear calibration diagram (see Fig. 3) by means of which the oxygen content at various depths can be determined with fairly good accuracy. It is recommended that anyone who starts using the apparatus should at the beginning make usual Winkler determinations of the oxygen content whenever the oxygen recorder is used. This is necessary because the ammeter values are dependent on the purity of the mercury and on the speed of the falling drops. The calibration curve, therefore, will not always go through zero. In water with sharp discontinuity layers it should never be possible lo determine salinity and oxygen content of such layers by means of the usual with any accuracy at all. This is because the water sampler itself is so long that it collects water of greatly varying properties. In such discontinuity layers only continuous recording can give the correct picture. Fig. 4 gives examples of curves obtained by the oxygen recorder.