SECTION 2.— GENERAL SURVEY OF THE PLANKTONIC PLANTS 

 (PHYTOPLANKTON) AND UNICELLULAR ANIMALS 



Unicellular pelagic plants, or, to use the more convenient term, "phytoplankton," 

 play as large a role in the natural economy of the Gulf of Maine as in other boreal 

 seas. Strangely enough, however, systematic collection and examination of them 

 in this particular region date back only to 1912 (Bigelow, 1914). Since then many 

 hauls of phytoplankton have been made in the offshore parts of the Gulf of Maine, 

 but time and the assistance available have so far allowed only a preliminary examina- 

 tion of these. Besides these records for the open sea in the gulf, McMurrich (1917), 

 Bailey (1910, 1915, and 1917), Bailey and Mackay (1921), and Fritz (1921) 

 have published valuable surveys of the phytoplankton (particularly the diatoms) 

 from the estuarine waters near the Canadian biological station at St. Andrews in the 

 Bay of Fundy, and in addition Doctor McMurrich has very kindly allowed the use 

 of his unpublished notes, to which frequent reference will be found in the following 

 pages. 



Gran (1912) has recently given such an excellent and readable account of the 

 phytoplankton of the high seas as a whole and of the role it plays in the economy 

 of nature that no general survey is called for here. Suffice it to say that these 

 unicellular algae are the chief marine producers (organisms, that is, capable of elab- 

 orating organic compounds from inorganic substances in sunlight) and the only 

 producers over the high seas outside the narrow coastal zone within which seaweeds 

 flourish. I do not know who first paraphrased the expression "all flesh is grass" 

 with the words "all fish is diatoms," but if not taken too literally it expresses the 

 fundamental truth that the whole system of animal life in the sea (as on land) depends 

 on plants in the last analysis and chiefly on the tiny unicellular algae, which we often 

 capture in millions in our tow nets. 



The groups that play the major roles in the phytoplankton of the Gulf of Maine, 

 as well as in other northern seas, are the diatoms and the peridinians, which alternate 

 in more or less regular seasonal succession, to be described below; and since the value 

 of the following account depends chiefly on the correct identification of the several 

 species, a word on this subject will be germane here. The diatoms are proverbially 

 a "difficult" group because fresh and brackish waters support a multitude of species, 

 which are separable one from another only by most painstaking study with the 

 microscope. Fortunately, however, although the planktonic diatoms are probably 

 the most numerous of all marine organisms in number of individuals, the species 

 occurring regularly in the plankton of northern seas are comparatively few, 21 while 

 those that dominate the northern planktonic communities at one time or another 

 (and these are, of course, the most important from both the geographic and the 



11 Gran (1908) lists about 170 species as typically pelagic in boreal-Arctic waters. 



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