314 
BULLETIN OF THE BUREAU OF FISHERIES 
SPRING AND FALL MAXIMA 
It is evident from the study of the diatom counts of Wolfe and Cunningham 
that they were high during the April cruise of 1916 and the March cruise of 1920 in 
Chesapeake Bay. While this conclusion is not reached from counts made daily in 
any one locality, it is based on many samples collected on each cruise in 1915-16 
and 1920-21. During 1915 the cruises were taken in October and December; 
during 1916 in January, March, April, June, July, and September; during 1920 in 
January, March, May, July, August, October, and December; during 1921 in January. 
The diatom counts were made on water samples collected at the surface and at or 
near the bottom. In addition, during 1915-16 counts were made of the individ- 
uals of each species at various depths. The results are expressed in the number of 
diatoms per liter of water. 
As an example, the diatom counts for area A at the surface were as follows: 
Year 1915, October, 4,300, December ; year 1916, January 13,600, March 17,000, 
April 558,300, June 9,200, July 6,200, September 92,800. The counts at 27 meters 
were these: October 99,400, December — — , January 39,800, March 26,500, April 
359,100, June 19,500. The maximum spring count was that of the April cruise 
both at the surface and at 27 meters, and there was a less marked rise in surface counts 
during the autumnal cruise. Autumnal records for 27 meters are lacking. 
A similar surface series at area A for 1920 is the following: January 16,500, 
March 262,600, May , July 8,300, August 14,400, October 21,300, December 
418,400. At the bottom these counts were found: January 19,700, March 229,400, 
May , July 27,000, August 32,800, October 3,100, December 43,600. Here 
again there was a markedly high count during the spring cruise of March and a fairly 
well-marked autumnal rise, which seems to have persisted into the winter months. 
The results of surface counts from area A are graphically shown in Figure 16. 
High counts were found in all regions (although not at all areas) over the bay in 
March, 1920, and there were fairly widespread evidences of similar conditions during 
the April, 1916, cruise. An autumnal rise probably occurred all over the bay but 
not so markedly in the upper part. The records of the different cruises often show 
successive increases from early fall into midwinter, and the suspicion arises in one’s 
mind as to whether the so-called autumnal rise is not the beginning of the spring 
maximum of the following year. As a matter of fact, data for 1915-16 and 1920-21 
indicate that the autumnal maximum did not occur until very late and that there 
may have been a close approach of the two maxima to one another. The results in 
the Chesapeake are veiy similar to those observed by Steuer (1910) for the Adriatic 
Sea and by Fish (1925) for Vineyard Sound, etc. 
SUMMER MINIMUM 
The decrease in the number of diatoms during the summer cruises was about as 
marked as the increase for the vernal cruises ; but occasionally, as has been observed 
by Gran in the Gulf of St. Lawrence, Fish at Woods Hole, Bigelow off Marthas Vine- 
yard and others, rather large numbers occur locally in the summer months. A slight 
but distinct increase in diatom counts was found in the upper part of the bay during 
July, 1920. If these increases were due to specially favorable conditions of food 
supply in the bay, resulting from exceptional outflow from rivers, it is of interest to 
note that during the month previous the rainfall in Maryland and Delaware was 
one and one-third times|the normal and that the summer was cool and wet, the 
wettest on record over southern Baltimore County. 
