216 



POPULATIONS OF THE SEA 



Southern NORTH SEA 



ATLANTIC 



J J A S O N O 



Thalassiothrix 



longissima 



Rhizosolenia 



hebstata semispina 



Ceratium tongipss 



CGratiurn tripos 



Ceratium furca 



Csratium fusus 



Ceratiurn macroc&ros 



Ceratium horridum 



Rhiz alata alata 



Rhiz. styliformis 



Biddulphia sinensis 



Calanus finmarchicus 

 Temora longicornis 



Centropages hamatus 



Acartia spp 



Para -Pseudocalanus 



Isias clavipes 



Labidocera wollastoni 



Centropages typicus 



Corycaeus spp 



JFMAMJ JASONO 



Tnalcssiothrix 



longissima 



Cerot'Um horridum 

 Rh z styliformis 

 Ceratium fusus 

 Ceratium furca 

 Ceratium tnpos 



Rhiz alata alata 



Rhiz alata indica 



Ceratium macroceros 



Calanus finmarchicus 



Para-Pseudocalanus 



Acartia spp 



Centropages typicus 



Candacia armata 



JFMAMJ JASOND 



Fig. 7. The average abundance of the common species of phytoplankton 

 (above) and copepods (below) in the southern North Sea and over the deep Atlantic 

 part of the Continuous Plankton Recorder Surve>. The histograms are based on 

 the combination of like months during the nine years 1948-1956. The height of each 

 monthly histogram indicates the abundance of each species related to the average 

 number per sample (of that species) for the whole period of 9 years (G. A. Robinson 

 and J. M. Colebrook, unpublished). 



abundance which I mentioned above. It shows the mean number 

 per sample, year by year, of Calanus finmarchicus and two species 

 of Ceratium in the southern North Sea. It is at once clear that the 

 Ceratium species fluctuated in a closely similar manner, and that 

 the numbers of Calanus varied in a different way which was to 

 some extent the inverse of the pattern shown by the Ceratium 

 species. 



By calculating correlation coefficients between all possible pairs 

 of species, Colebrook and Robinson have found that there was a 



