BIOLOGICAL STUDY OF CHESAPEAKE BAY WATERS 
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times when the coastal plain was more elevated than at the present time. While 
there does not seem to be any good reason for believing that the ebb and flood of the 
tide during recent times has cut the deep channel, yet it is known that erosion to a 
marked degree is taking place along the eastern shore of the bay (Hunter, 1914). 
Like most estuaries, Chesapeake Bay has, in general, a muddy bottom, resulting 
in part from the deposition of large amounts of organic matter brought down from 
the land by the rivers; in part from the settling of the dead bodies of marine, brackish- 
water, and fresh-water organisms, and in part from the settling of finely divided 
mineral matter. The latter is commonly called clay. This mixture of clay and 
organic matter, which assumes a soft, sticky condition when wet, undoubtedly con- 
tains some iron sulphide resulting from the action of the sulphates in the sea water 
on the iron compounds brought from the land. The mixture is characteristic of 
estuaries, ocean waters near the land, and deeps outside of the 100-fathom line, accord- 
ing to Murray and Irvine (1893). They have given it the name “blue mud” or 
clay. This “blue mud” varies somewhat in color from a black to a blue-black and 
to a brown in the Chesapeake, depending, probably, on the amount of organic matter 
and sulphide of iron present, as pointed out by Murray and Irvine. 
The consistency of the blue mud is not the same in all regions. In some places 
it forms a rather firm, cakelike layer without a soft surface, in others the typical 
plastic, claylike mud with a soft surface, and in still other localities a soft, puddled 
mud. Samples of the bottom of Chesapeake Bay show, as a rule, that the blue-mud 
layer is not very thick except in certain regions, such as the mouths of rivers. Usually 
a sample cut out of the bottom to a depth of 2 or 3 inches shows a lower layer of sand, 
clay, or shells, and often the blue mud is more or less mixed with these materials. 
While the bottom of Chesapeake Bay is largely muddy, the shores are usually sandy, 
and this latter condition is especially characteristic of the southern half of the bay. 
The movements of the water of Chesapeake Bay are complicated. The ebb and 
flood of the tide, the outflow of many rivers which aid the ebb and hinder the flood, 
the greater volume of river water entering from the western shore, eddies produced 
by headlands at the mouths of rivers and inequalities on the bottom, currents moving 
in more or less opposite directions at surface and bottom in the same locality, varia- 
tions in rainfall, seasonal changes in temperature, and strong winds are factors which 
govern the movements of the water in the bay. There are no very strong currents, 
a condition which has been noted by the Coast and Geodetic Survey (1916), Grave 
(1912), and the author. 
METHODS 
Some preliminary investigations of much value were made by Lewis Radcliffe, 
of the Bureau of Fisheries, in 1915, 1916, and 1917, but this work was discontinued 
in March, 1917. In January, 1920, the writer continued the investigation under 
the United States Bureau of Fisheries and was in charge until March, 1922. 
During 1916 and 1920, 13 general cruises over the bay were taken on the U. S. S. 
Fish Hawk. In addition to these, 2 preliminary cruises were made in 1915, another 
on the U. S. S. Roosevelt outside of the bay near the entrance in 1916, 4 special cruises 
in the bay to study hydroids in 1916, 2 special cruises in 1921, and 2 in 1922. The 
24 cruises, including dates, station numbers, and other data, are given below: 
Cruise 
I. October 22-27, 1915, stations 8336 to 8365. 
II. December 1-10, 1915, stations 8366 to 8402; 24-hour station 8394. 
III. January 15-22, 1916, stations 8403 to 8441. 
