212 DISCOVERY REPORTS 



of the fjord was known to have a high oxygen content at that time (Table LV, Sts. MS 94 

 and 96). The abnormally low surface phosphate at St. MS 97 also lent support to this 

 view, as the surface water of Moranen Fjord was also found to be comparatively poor m 

 phosphate. It is possible that conditions in the fjord are much more stable than those 

 in the open bay, permitting the development of a richer phytoplankton. Some support 

 for this view was furnished by the pB. values, which were much higher in the surface 

 water of the fjord than any observed in the bay. However, there was no evidence of the 

 efflux of such phytoplankton at St. MS 97, so that if the conditions in the fjord were, in 

 part, the product of a rich phytoplankton development, as the diatom hauls at St. MS 94 

 suggested, it is fairly certain that this development must have ceased by the time St. 

 MS 97 was worked. 



The falling off of the diatom catches after mid-season coincided with a considerable 

 rise in the mean value of the temperature. This again indicates land drainage as an un- 

 favourable factor, but it is also possible that higher temperatures in themselves have a 

 deleterious effect upon diatom growth. Rise in temperature will greatly increase the 

 rate of respiration, whereas the rate of photosynthesis, limited by the amount of carbon 

 dioxide available, cannot rise to the same extent. Thus the condition is obtained that 

 extensive accumulation of food reserves is only possible at the lower limits of the 

 organisms' temperature range (Dr W. H. Pearsall in correspondence). With the inshore 

 plankton so extremely scanty it is probable that this factor would never be of the first 

 importance in an area like East Cumberland Bay, but it is highly probable that tem- 

 perature plays an important part in the open sea ofT South Georgia, either in some such 

 way as is outlined above, or by its action on the degree of polymerization of the water 

 molecules as outlined in the main part of this paper (pp. 191, 192). 



Returning to East Cumberland Bay, the mean phosphate content of the upper layers 

 showed a steady fall during the first half of the season (Fig. 84), similar to that observed 

 by Clowes when working on the shore water at Hope Point. During this time the pro- 

 duction of neritic diatoms was at its height (Fig. 81). This diatom production, however, 

 never approached in extent that found offshore, so that it is probable that other factors 

 besides utilization by phytoplankton were at work in bringing about this reduction of 

 phosphates. From the consideration which follows it appears that the gradually in- 

 creasing amount of thaw water from the glaciers and snow-slopes discharging into the 

 bay may be responsible. 



In Fig. 84 the salinity and phosphate values at the surface are plotted below the wind 

 components. It will be seen that up to St. MS 98 the relation between surface salinity 

 and wind was very close. The change in phosphate values was not so pronounced, and 

 the slight falling off at St. MS 86 when the salinity was still rising with a northerly wind 

 was due to the relatively large amount of outside plankton present at the time. The 

 anomalous conditions apparent at St. MS 98 and some subsequent stations, were due 

 to intervention of other factors. Chief among these were the efTect of wind during the 

 interval between stations, and, occasionally, the presence of drifting glacier ice. 



At St. MS 98 phosphate was high after northerly winds, but the surface salinity was 



