The Animal Ecology of the Cold Spring Sand Spit 



wide, and at mean high tide has a prevailing depth of less than 2.5 meters. Its sandy 

 bottom is for the most part covered with half a meter of fine black mud. This is 

 largely exposed at low tide, and supports an abundant growth of "sea cabbage" 

 (Ulva). The specific gravity of the water at high tide varies from 1.018 near the 

 entrance to the inner harbor to 1.005 at the surface near the inlet of the creek. Near 

 the "gut" where the tides rush in and out of the inner harbor the bottom is kept 

 scoured and consists of gravel and stones. Outside the sand spit the water has a pre- 



Fig. 2. — View of Cold Spring Harbor at high tide looking north. The inner harbor is in the foreground ; between 

 it and the outer harbor is seen the sand spit. Close to the sand spit on the inside is a fringe of Spartina polystachya. 



vailing specific gravity of 1.019 and is about 6 to 8 meters deep at high water. A 

 bar (Fig. 2), almost submerged at high tide and consisting largely of hard mud, has 

 formed opposite to the outer entrance to the gut and affords a "shallow sea" fauna. 



The sand spit itself (Figs. 2 and 3) is 660 meters long and varies in width from 

 80 meters at its western end to 15 meters at its eastern end at high water. The 

 prevailing width is about 40 meters. The highest part of the spit is about one meter 

 above mean high tide, and the average height of tide is 2.4 meters. The slope is 

 gradual on the outside (north side), it being 40 meters from high to low water at 

 the western third of the spit. The slope increases to 2.4 meters in 15 at the eastern 

 end. The material of which the spit is built is sand, which at the western end 

 contains much gravel, apparently because of the greater carrying power of the surf, 

 which is highest here. At the gut the sand is very coarse on account of the rush- 

 ing tide. In the middle stretches of the beach the sand is finer. On the inner face 

 of the spit mud is deposited. On account of the sandy beach and the currents and 

 surf that are washing it all the time, no plants grow on the outside of the sand spit 



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