PHYTOPLANKTON OF EAST CUMBERLAND BAY 205 



component of the wind is negligible, heavy precipitation may lower the salinity very 

 considerably without the aid of wind of a definite southerly trend, as at St. MS 102. 

 South-easterly winds bringing water (and often floating ice as well) over from the 

 Nordenskjold glacier produced the lowest surface salinities of all. 



Conditions in the bay change so rapidly that observations at much closer intervals 

 would be necessary in order to keep track of all the changes going on, and as other work 

 was in progress at the same time it was not possible to attempt more than one station 

 per week. However, the broad outlines of the above argument seem to hold good, and 

 to render the changes in the nature of the plankton observed during the first half of the 

 season intelligible. 



With strong winds of a pronounced northerly or southerly trend, the changes were 

 so rapid as to necessitate only the wind on the day of the station itself being considered, 

 but with light winds the conditions set up by the winds prevailing during the preceding 

 days may still persist when the station is worked in the morning. Thus at Sts. MS 97 

 and loi, which furnish apparent exceptions to the general rule above enunciated, 

 reference to the diagrams and to the Station List shows that at both of them the wind 

 on the day of the station was slight, that they were worked early in the day, and that the 

 conditions conform to theory when the prevailing winds of the preceding days are taken 

 into account. 



In the following account of the eff'ect of the wind throughout the season, it is necessary 

 to make constant reference to Figs. 81, 83 and 84, and occasionally to the Station List. 

 Fig. 81 gives the total diatoms as histograms, Frogiloria sp., the principal neritic form, 

 being shown in black; above are given the north and south components of the wind, 

 curves for the mean salinity and temperature of the upper 20 m., the hours of sunshine, 

 and the precipitation in mm., for the interval between each station. Fig. 83 shows the 

 probable distribution of the isohalines with depth throughout the season, based on the 

 salinity determinations from depths down to 75 m. at each station, and the wind com- 

 ponents above. 



It will be seen that at St. MS 84 (November 12) a fight south-easterly breeze pre- 

 vailed, the salinity in the upper layers was low, and Fragilaria sp., the typical neritic 

 form, predominated in the plankton. At the next two stations with northerly winds, 

 there was a rise in the mean salinity value for the upper 20 m. and a considerable in- 

 vasion of oceanic diatoms, while Fragilaria sp. showed but slight increase in numbers. 

 The richest diatom catch of the season was obtained at St. MS 86, the immigrant 

 Chaetoceros criophiliim being dominant. This form was exceedingly abundant in the 

 open sea off South Georgia at that time. 



At St. MS 87, despite a moderate northerly breeze with high salinity, there was a great 

 falling off in diatoms, and in the scanty material obtained Fragilaria sp. again pre- 

 dominated. This is explicable on the grounds that during the interval between the two 

 stations wild weather from the south-east prevailed, eflfectively driving out the com- 

 paratively rich phytoplankton found at St. MS 86. This change was also reflected in 

 the drop in temperature of the upper layers. 



