402 



BULLETIN OF THE BUREAU OF FISHERIES 



density of the eastern diatom center, reflected by the volumes of plankton, and 

 more especially the rather large volumes along the 100-meter curve west of Nova 

 Scotia contrasted with the barren water both over the basin to the west and close 

 in to the neighboring coast on the east, point directly to a tonguclike drift of diatoms 

 northward toward the Bay of Fundy from the rich center of production off Cape 

 Sable. 



The rich catches in the Eastern Channel (375 cubic centimeters at station 

 20107) and off the southeast face of Georges Bank (290 cubic centimeters at station 

 20109) similarly suggest another line of dispersal for the Cape Sable-Browns Bank 

 diatoms toward the southwest, a thesis supported by the qualitative uniformity of 

 the April catches in that region, illustrated by the following table: 



If such a drift of diatoms from the Nova Scotian center was actually taking place 

 at the time of our April cruise in 1920 it must have been strictly confined to the outer 

 edge of Georges Bank, because the shallows to the northward (stations 20108, 20110, 

 and 20111) supported a phytoplanktonic community not only much less abundant 

 (15 to 120 cubic centimeters per haul), but one of rather a different type, in which 

 the oceanic diatoms Clisctoceras decipiens, C. eriopliillum, C. aflanficum, C. densum,, and 

 Coscinodiscus were dominant, with the several species of Ceratium continuing as an 

 important factor in April just as they had been in March. 



As long as the diatom flowerings continue at their peak, volumes of plankton as 

 large as or larger than those noted on the chart (fig. 109) are to be expected all along 

 the coast north and east of Cape Ann, on the one side of the gulf and over the banks 

 west and southwest of Nova Scotia on the other (Browns Bank yielded one of our 

 largest spring catches, as appears on the chart), locally, too, on Georges Bank (p. 3S5); 

 and while the central part of the gulf is hardly less barren in April than in March, the 

 spring flowering may be no less intensive there, once it is under full headway, than in 

 the coastal zone. For example, diatoms were so plentiful in the western basin on 



