Papers in Marine Biology and Oceanography, Suppl. to vol. 3 of Deep-Sea Research, pp. 58-67. 



Seasonal changes in the phytoplankton as indicated by 

 spectrophotometric chlorophyll estimations 1952-53 



By Pamela G. Jenkins 



(Introduction by W. R. G. Atkins) 



Summary — Estimations of the chlorophyll content of the phytoplankton in the English Channel 

 at station El were continued from September 1952 until August 1953 at ten depths from to 70 m. 

 As before, the species of the phytoplankton were identified by a culture method. 



Minima of about 2 mg/m^ occur in winter and in June. Maxima at particular depths can occur in 

 March, April or May, thus in 1952 the maximum was in a March surface sample, 34-2 mg/m^, 

 whereas in 1953 sinking of the cells gave, in May, 78-8 mg/m*. The quantity found can be much 

 influenced by the date of sampling. An autumn maximum late in September 1952 gave 21-1 mg/m^ 

 at the surface. 



The collodion filter disks varied in colour from dark grey or chocolate to a light sandy colour and 

 examination with a low-power microscope shows phytoplankton, stray fibres and sometimes copepods 

 and other animals. Copepods were counted in spring and summer, a maximum of 24 on one disk 

 being found at 25 m on April 27, got from two litres of water. The figures for the column indicate 

 about 300,000 per square metre down to 70 m. 



The botanical composition of the phytoplankton was studied by the repeated examination, from 

 first signs of growth onwards, of the chemically enriched samples placed in diffuse daylight. Fifty- 

 four species of Bacillariphyceae were recorded. As before Skeletonema costatum, a Navicula sp. and 

 Nitzschia closterium were the most common. Many species of Chaetoceros were identified in the 

 autumn of 1952. 



Six species of the Chlorophyceae, five of the Chrysophyceae, one of the Cyanophyceae and three 

 of the Cryptophyceae were recorded. The most common species of the first class was a Chlorella, 

 and of the second a species of Coccolithophora grew in each sample. Phaeocystis globosa grew from 

 January to May. The member of the Cyanophyceae was an Oscillatoria. Neither this nor Phaeocystis 

 was recorded for El in the previous year. Hemiselmis rufescens appeared once more. 



INTRODUCTION 



In this " Festschrift " number it may well be pointed out that the roots of the science 

 of the sea are sunk deep in time. The adequate study of the sea involves all the exact 

 sciences, including even astronomy, and all the biological sciences. 



It is not, as often considered, a preserve for zoologists. The early devotees of the 

 study of marine life were just biologists, mainly systematists, for of necessity one must 

 follow Adam and name things. The beautifully illustrated papers of the early workers 

 are highly educational, and remind one that it is not for us to misquote and say, 

 " Surely we are the people and wisdom shall die with us ". I recall with sadness a 

 morning in April 1941 when, in smoking Plymouth, I picked up one page of an old 

 biological work — all that remained of our Athenaeum Library, which had housed so 

 much of the older literature. 



Perhaps Dr. Bigelow may be considered as having begun at about the end of the 

 old era of amateur biologists. He was studying the phytoplankton of the Gulf of 

 Maine in 1913. He found the entire basin occupied by a peridinian plankton, but 

 never found diatoms in abundance in July or August except close along the coast and 

 on Georges Bank. 



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