Methods

• Samples of Litorina littorea were taken at Nahant, MA, at the Northeastern University Marine Science Center.  This study was first conducted in late September, with an additional replicate day in mid November.  Samples were collected at or before low tide, dependent only slightly on cold, wet weather conditions.

• The tidal zone was measured with a 60 meter transect.  That measurement was divided into three zones: low, medium, and high.  At every meter, a 31 cm2 quadrant was placed on the center of the meter mark and was used as the sample area.  All L. littorea inside each quadrant were collected.  L. littorea were collected from each tidal zone and stored in separate Tupperware containers until they could be measured with a digital caliper. 

• The shell height and width were measured for each individual. A significant correlation was found between these two values for every tidal zone on both days (click here to see correlation values).  Because these two values had such a high correlation, the remainder of the results were analyzed using height. 

• To access the distribution of snail height in the three tidal zones, a series of graphs were created. T-tests were used to analyze differences in distribution of snail height in the three zones for each day.