BIOLOGICAL STUDY OF CHESAPEAKE BAY WATERS 
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of the bay. While the various species making up these total counts have not been 
identified, it is safe to say that the counts include fresh-water, neritic, oceanic, and 
semibottom diatoms. We have no data to show that the higher counts at area A, 
where the water was most saline, were due mainly to neritic and oceanic diatoms 
carried in at the time from the ocean and consequently adapted to a sea water of 
higher salinity. It is possible also that some of the neritic forms were produced 
locally from resting spores. Furthermore, the differences may be due to differences 
in nutritive value of the water or to other factors. Occasional surface counts made 
at areas B and C, especially during the spring maximum, did not always support the 
relation pointed out above. Deep-water counts were not made at equivalent depths 
on the east and west sides of the bay, so they are useless in this connection. 
COMPARISON OF DIATOM COUNTS AT MOUTH AND INSIDE THE BAY 
A comparison of the diatom counts found along the line E, F, G, in the mouth of 
the bay, with those along the line A, B, C, D, which runs from Cape Charles City to 
New Point Comfort, farther inside the bay, would be of interest in order to see if the 
numbers are higher in the mouth of the bay during the autumn and winter cruises 
when, as a rule, the salinities are higher, the incoming current is more dominant, and 
the Gulf Stream Eddy (Atlantic gyral) is shifting in a northerly direction. At such 
a time one might expect larger numbers at the mouth, if the bay receives any con- 
siderable supply of diatoms from the outside. Only during March, 1916, and Jan- 
uary, 1920 which were months of high salinity, have higher counts been found along 
the line E, F, G, than along A, B, C, D. The differences were small and the data too 
meager for a satisfactory comparison. It is true that the oceanic diatoms (see the 
section on the relation of distribution of species to the hydrographic data) which can 
be taken as an indication of the influx of oceanic water have been found almost 
exclusively during the months when water of higher salinity was making its way into 
the bay, yet the lack of diatom counts for some of the areas along the lines E, F, G 
and A, B, C, D on every cruise, the absence of data on the species found, and the 
rather limited current data from 24-hour stations make further work necessary before 
any definite conclusions may be reached. 
The Atlantic water that enters the bay, judging from our salinity data, is not 
pure oceanic water. Salpa, which is commonly found in the oceanic water of the 
Gulf Stream off the mouth of Chesapeake Bay, has not been found in the bay, and 
true oceanic diatoms during 1916 at least were scarce. 
RELATION OF DISTRIBUTION OF SPECIES TO HYDROGRAPHIC DATA 
The data on the number of individuals of each species are limited to the cruises 
of October and December, 1915, and January, March, April, June, July, and Sep- 
tember, 1916. During October, 1915, counts were made for each species of diatom 
from the surface to the bottom at 9-meter intervals for areas A, J, L, and R. Counts 
were made also at many other areas during the cruises for 1916, but there was con- 
siderable irregularity in the choice of areas and the number of samples. However, 
the depths at which samples were taken were practically without exception at 0, 9, 18, 
or 27 meters, thus corresponding with those for October, 1915. Almost invariably 
only two counts were made for each species at each area during 1916 — a surface count 
and one at 9, 18, or 27 meters, depending on the depth at the area. 
