BIGELOW: COAST WATER EXPLORATION OF 1913. 265 
uniformity from season to season. Below say sixty fathoms the 
extreme range of temperature over the entire Gulf, throughout the 
year is probably not over 10° (88°-48°); at 100 fathoms the extreme 
range is about 8° (38°-46°). And the deep parts of the western half 
of the Gulf are still more uniform; the extreme temperature variation 
at all depths below sixty fathoms, being not more than 4° in the basins 
and troughs next the western shore. Salinity, too, is surprisingly uni- 
form in the deeper parts of the Gulf. In short, the fauna which 
occupies these depths enjoys an environment whose physical factors 
are practically unchanging from year’s end to year’s end. 
But quite the opposite is true of the surface layers of the Gulf, 
where there are violent seasonal fluctuations of both temperature 
and salinity. Along the western shore, and in Massachusetts Bay, 
the surface temperature rises from about 36° in winter to 63° or 64° in 
summer, 2. ¢., a range of almost 30°. -And though the annual range is 
smaller along the eastern side, it is still considerable. The salinity, too, 
oscillates between wide limits, and the changes are very sudden in 
spring. For example, north of Cape Ann, the range is from about 
32.8% o in February to about 29%p early in May. 
In addition to these regular seasonal changes, the Gulf is subject to 
sporadic invasions, on the one hand by water from the Gulf Stream, 
with its characteristic fauna, on the other by St. Lawrence water. 
But these are not extensive enough to cause much change in the Gulf 
as an environment, though they do alter the faczes of the plankton 
by the addition of either southern, or northern organisms, as the case 
may be. 
South and west of Cape Cod there are no parts of the continental 
shelf where the water is as uniform, from season to season, as it is in 
the deeps of the Gulf of Maine. On the contrary, the entiré water 
| mass over the shelf is subject to violent fluctuations, both seasonal 
\/and sporadic. These are most violent, of course, near the surface and 
| next the coast. For example, the surface temperature off New York 
| ranges from about 38° to over 70° during the year; the salinity from 
about 31% to possibly 34% . And even as deep as sixty fathoms the 
| temperature may rise from below 45° to nearly 60° in a month (p. 349), 
| the salinity from 33.5%o to 35.1%p in the same short period. And 
| this general statement is true all along the coast, at least as far as 
Chesapeake Bay. Thus any bottom animal may be subjected to 
\ great and sudden changes. At the edge of the shelf, where the water 
‘is deeper (75-125 fathoms), conditions are more uniform. And this 
is a particularly interesting zone zodlogically, as Verrill (1880, 1884a) 
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