ORGANIC PRODUCTION IN THE BENGUELA CURRENT 285 



Stephanopyxis turns were present than in spring. One noteworthy feature is that the richest stations 

 on survey I were found in the coastal waters between 23 and 26 S. where the effects of heating and 

 mixing with more saline water were clearly recognizable. Even amidst this dense flora, relatively 

 great quantities of phosphate were recorded. In this area, as we have noted, many moribund plankton 

 organisms and lines of foam, probably accumulations of dying phytoplankton, were observed on the 

 sea-surface, and the conditions would, therefore, have been conducive to a rapid regeneration of 

 nutrients from the decomposing plankton (Seiwell and Seiwell, 1938). Many resting spores of 

 Chaetoceros didymum and C. subsecundum occurred in the plankton samples, but we have insufficient 

 data to decide whether these were associated with such conditions or merely exhibit the seasonal 

 change in autumn. 



The development of the peak population under such conditions is not altogether surprising, for 

 even with uninhibited exponential growth it must take some time for diatoms to reach such dense 

 concentrations in a newly upwelled water mass, and on this occasion the greater age of the upwelled 

 water and higher temperatures would have favoured such a development. 



On both surveys the contrast between the densities of the coastal and oceanic populations of phyto- 

 plankton was an outstanding biological feature of the region. It should be specially noted that on 

 survey I the coastal populations reached a figure some four orders of magnitude greater than those in 

 the oceanic waters, and on survey II the range was three orders of magnitude. The actual figures 

 are given in Tables 14 and 15 (pp. 224 and 230), and their distribution in Figs. 57 and 65 (pp. 225 

 and 231). 



Even the crude settlement volumes of the net hauls (Tables 14 and 15) suffice to show that the rich 

 inshore phytoplankton of the Benguela current is roughly comparable in quantity to that found in the 

 Peru current (Gunther, 1936) and in the more oceanic waters of the antarctic zone during the main 

 increase (Hart, 1934, 1942). They are significantly poorer than those found in northern antarctic 

 coastal waters (South Georgia) in late spring, but much richer than the values recorded there during 

 the post-maximal decrease and in winter. In the Benguela coastal waters there seems to be but little 

 seasonal falling off in quantity so long as the surface-layers are replenished by upwelling, so that it is 

 quite probable that the total annual production there equals or even exceeds that of the South Georgia 

 area, though the latter (at the height of the spring increase) can amount to 7-10 times the Benguela 

 or Peru averages. These figures from South Georgia in fact furnish by far the greatest standing crop 

 values yet known to us from any part of the world. 



The open ocean, we know, presents a relatively stable and uniform environment and this in turn 

 appears to be accompanied by stability in the biological processes occurring in these waters. On the 

 other hand, the dominant physical feature of upwelling regions is their irregularity even under normal 

 conditions and this is paralleled with a constantly changing biological picture. 



Unfortunately our knowledge of the upwelling process is still far from being quantitative and until 

 we can measure the processes of advection, eddy diffusion and mixing in the upwelling water we can 

 go no further than to describe a very generalized picture of the environment and conjecture about the 

 processes occurring therein. 



Nor do the biological phenomena lend themselves to ease of measurement, continually undergoing 

 rapid and extensive fluctuations. Steeman-Nielsen and Jensen (1957) have shown how the high- 

 standing crop of phytoplankton is accompanied by a high rate of primary production. The transfer 

 of organic matter through the organic cycle is initially dependent on the grazing of the herbivorous 

 animals, and the success of the transfer depends on the efficiency of the grazing process. The high- 

 standing stock of higher animals in the area shows that the extent of the grazing must be very great. 

 Nevertheless plants which are not eaten eventually sink, die and decompose, and in the bottom deposits 



