Chapter II—SOME FACTORS AFFECTING THE DISTRIBUTION OF ALGA! AT 
WOODS HOLE AND VICINITY. 
1. THE COAST. 
The shore line of Woods Hole, of the Elizabeth Islands, and of neighboring regions 
along Vineyard Sound and Buzzards Bay is in some respects remarkably varied (see 
chart 225), but lacks certain important physical features present in other localities. 
The coast, wherever exposed to wave action or tide currents, is composed of bowlders 
and stones or consists of sandy and stony beaches. This is because the bowlders and 
stones have remained at the shore line as the finer material of the glacial deposits covering 
this region was washed away by the erosion of the coast. The sheltered coves, bays, 
and harbors will generally have a sandy or muddy shore, sometimes gravelly, with scat- 
tered groups of stones or bowlders. There are also small salt marshes connected with 
some of the coves, as at Quisset and Hadley Harbor. There are no outcroppings of 
rock, except in the vicinity of New Bedford Harbor, to make possible perpendicular 
or slanting ledges and rock pools. An account of the geography of the region, together 
with the character of the shores, is given in section I, chapter II, pages 28 and 29. 
For the reasons stated above one misses some of the very characteristic associa- 
tions of alge which may be noted in tide pools and along the sides of rock masses where 
there is opportunity for the development of conspicuous bands or zones of vegetation 
between tide marks and below—associations that are well illustrated in such localities 
as Newport and at Nahant, near Boston. A shore of bowlders presents a broken line 
at the water’s edge which can not show to full advantage the distribution of algz in 
zones. There are good illustrations of zonation in places, but they are on a comparatively 
small scale and become evident only as groups of rocks or parts of the shore are studied 
in detail, as was done for Spindle Rocks in the harbor of Woods Hole, to be described 
later (pages 476-479). Another factor that works against the conspicuous zonation 
of algee in this region is the relatively small tide, which does not give much opportunity 
for the development of broad zones of differentiated algal growth. 
2. THE BOTTOM IN DEEPER WATER. 
As would be expected in an area of glacial drift, the bottom offshore and in the 
deeper portions of Buzzards Bay and Vineyard Sound may consist of sand, gravel, or 
stones, with or without deposits of mud, but is frequently of a more or less mixed or 
spotted character. Channels swept by swift tides are likely to be stony and sandy, 
while sheltered coves, bays, or other regions, free from the scouring action of tidal 
currents, usually have a muddy bottom. The ledges or other areas composed of bowl- 
ders are simply pi'es of stones heaped together where they were laid after the finer 
matrix of the glacial drift had been washed away. The muddy bottoms are due to 
deposits of silt where the water is sufficiently quiet because of its depth, or because of 
the absence of tidal currents or wave action sufficiently strong to prevent the accumu- 
445 
