NATURE ADRIFT 



(a) The Natioplaiiktoii * 



These are extremely tiny plants, mostly between i/io,ooo inch and 

 i/i,ooo inch, very delicate and capable of swimming often several times 

 their own length in a second. As they are so minute, they are measured in 

 'fx' units {ijiJt^= I / 1, 000 millimetre). Those with one or more flagella are 

 often termed '/x flagellates' or hekistoplankton. A flagellum is a whip-like 

 hair which lashes the water in one direction and flexes as it returns for the 

 next beat, so enabling the organisms to swim in any direction. Planktonic 

 organisms, bacteria excepted, less than lo /^ arc included in the nanoplankton. 

 The smallest known are only about i /x and are thus difficult to study even 

 with an extremely good microscope. Electron microscope studies have, 

 however, improved our knowledge of their structure considerably. Draw- 

 ings of some arc given in Fig. 7. 



In spite of their small size, the nanoplankton is of great importance in the 

 sea and it has been estimated that their total volume is at times about equal to 

 and sometimes greatly exceeds that of the diatoms and dinoflagellates 

 together. This will be more fully discussed in Chapter 9. 



Because the discovery of nanoplankton is fairly recent and has been studied 

 by only a very few experts, we still know very little about it. If you 

 yearn to discover and name new species you should choose this field, for the 

 numbers may well be limited only by the time given to them ! We know so 

 little about their physiology too, a most important field of study. Their 

 very simplicity of structure makes it possible to investigate in pure cultures 

 some of the little-known but highly comphcated problems of vitamin 

 requirements and vitamin production that could give clues to similar prob- 

 lems in higher plants and animals. 



One of the best known is probably Cliroiiniliiia piisilla, one of the smallest, 

 only i-i|)Li; it was first named as one of the Chrysophyceae (orange or 

 yellow plants) in 1952 by Butcher from studies made with the ordinary 

 microscope. Research in 1959 with the electron microscope and biochemical 

 tests have shown that it is not a member of the Chrysophyceae at all, but its 

 affinities are nearer the Chlorophycae (green plants) to which most plants 

 belong. C. pusilla is extremely abundant in coastal and open sea waters near 

 the British Isles and probably in a much wider area. Figure 7; ici and 

 b show its general shape, a single cell with its one nucleus and a highly 



* The term nanoplankton is not based on botanical characters but is merely a con- 

 venient size grouping. It is derived from the Greek 'n'anos' meaning dwarf, and was 

 coined by Lohmami in 191 1 as 'nannoplankton', thus introducing a misspelling which 

 should surely be corrected, although some purists argue that the way Lohmann spelt 

 it should be the valid term even if wrongly derived. 



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