PLANKTON OF THE GULF OF MAINE 



405 



only 2 to 3 cubic centimeters at a neighboring locality on August 31 (station 10306). 

 Though the eclipse of Skeletonema left the phytoplankton hardly richer at the mouth 

 of the bay in that October (volume about 4 cubic centimeters on the 26th, in 1915, 

 station 1033S) than it had been at the end of August, it is probable that a general 

 increase over its midsummer state takes place in the volumes of phytoplankton of 

 Massachusetts Bay in late autumn, because peridinians, chiefly Ceratium tripos, 

 were abundant enough there in November, 1916, to yield volumes of 18 to 20 cubic 

 centimeters on the 8th (stations 10403 and 10404). 



With the fading temperatures of winter the volume of phytoplankton as a whole 

 shrinks to its annual minimum in all parts of the gulf which we have visited at that 

 season; so much so that the greatest measured volume for the winter cruise of 1920- 

 1921 (stations 10489 to 10502) was only 6.5 cubic centimeters (station 10488), and 

 ranged down to less than 1 cubic centimeter per haul at the other stations, as follows: 



Having made no vertical hauls for the phytoplankton in the Gulf of Maine, 

 counting of diatoms or of peridinians has not seemed worth while. Fritz's (1921) 

 counts of diatoms in the Bay of Fundy are likewise based on horizontal hauls, and 

 hence do not represent the number present in any known volume of water; but Peck 

 (1896) made a quantitative study of the diatoms of Woods Hole and Buzzards Bay 

 based on the filtration of large samples (5 liters each) of sea water through a sand 

 filter. 34 



Unfortunately, Peck's tables do not give the actual counts per sample, but are 

 based on combinations of the several samples for a given level — surface, inter- 

 mediate, and bottom — at all four stations and for all these levels combined for each 

 station. On averaging them, however, it appears that the largest catches of diatoms 

 were at least 420,000 per liter — that is, 420,000,000 per cubic meter of sea water. 



To give the reader a more concrete idea of the numerical strength to which 

 marine diatoms may attain when flowering actively, some of the oft-quoted counts 

 for European waters will not be out of place here. One of the richest catches ever 

 recorded, Johnstone (1908, p. 210) tells us, is Brandt's (1902, p. 71) of 3,173,000,000 

 diatoms, besides 500,000 peridinians and a few thousand copepods, in a net 1 square 

 meter in mouth diameter, hauled up vertically from 30 meters, which, says Brandt, 

 indicates an actual diatom flora of at least 6,000,000,000 per cubic meter of sea water 

 after allowing for imperfect filtration by the net. To make these collossal numbers 



" Essentially the Sedgewick-Rafter method, for an account of which see Whipple (1905, p. 15). 



