624 
BULLETIN OF THE BUBEAU OP FISHEKIES 
would have occupied the upper 10 meters from end to end, instead of showing the 
chilling effect of the strong tides, which actually characterize its Cape Cod end. 
In the July profile (fig. 65) the cold bottom water is banked up against the 
southern side of the bay, but against the northern side on the profile for August 
(fig. 66) . A difference of this sort probably reflects a corresponding difference in 
the movements of the deep water around Stellwagen Bank. Judging from experi- 
ence in other years, the state illustrated by these August stations is the more usual 
in summer. 
BOTTOM TEMPERATURE 
'Stations 
Meter O 
The bottom temperature of the gulf in summer is governed chiefly by the 
depths, but also to some extent by locality. At this season the bottom is coldest 
(3° to 5°) in the 
troughs off the west- 
ern shore of the gulf, 
irrespective of depth, 
and in the offing of 
Cape Sable in the 
opposite side, with 
the whole deep basin 
1° to 3° warmer out- 
side the 150-meter 
contour (5° to 8°). 
For example, an ani- 
mal living in the 
trough off the Isles 
of Shoals might actu- 
ally suffer lower tem- 
peratures during 
some summers than 
in some winters or 
springs, according as 
Fig. 65. — Temperature profile crossing the mouth of Massachusetts Bay just west of Stellwagen the years be Cold Or 
Bank, July 19, 1916 (stations 10340 to 10342). The contour of the bank is represented by the warm in the £ulf 
br ° keECUrve The annual differ- 
ences in the basins at depths greater than 175 to 200 meters consequent on irreg- 
ular pulses in the bottom current may so overshadow the regular seasonal cycle as 
to make the latter negligible, biologically, up to the end of the summer. Bottom 
dwellers in the coastal zone, however, must be inured to a wide range of temperature 
if they are to survive; as, indeed, they must in shallow boreal waters in general. 
Cape Cod Bay experiences a wider fluctuation in bottom temperature, with the 
succession of the seasons, than any other part of the open gulf outside the estuaries 
and islands. In order to exist there, without bathic migration, in water shoaler 
than 5 to 10 meters, any animal must be indifferent to temperatures as high as 18° 
to 19° in midsummer (p. 623). A bottom temperature of 17.9° was even recorded 
as deep as 13 meters off Barnstable on August 24, 1922 (station 10644) — an extreme 
