(full paper is archived in the Miller Library)
Title: Distribution, abundance, and size classes of the intertidal gastropods, Tricolia pulloides and Barleeia haliotiphila
Student Author(s): Firestone, Alan L.
Faculty Advisor(s): Baxter, Chuck
Location: Final Papers Biology 175H
Date: June 1979
Keywords: midtide forest community
Abstract: 1. Tricolia pulloides and Barleeia haliotiphila are the two most common gastropods of the mesofaunal community associated with the mid-intertidal algal turf. Studies done on their distribution and abundance with respect to tidal height, algal species inhabited, and degree of wave exposure. 2. On a vertical face of algal turf Barleeia is significantly more abundant than Tricolia where their distribution overlaps by height and on algal species. For horizontal surfaces of algal turf they are not significantly different. 3. When compared on vertical algal turf Barleeia (+4.0 ft.) occurs 1.5 ft above Tricolia (+2.5 ft.). 4. Pt. Pinos, an exposed area, has significantly greater densities of both species than does Mussel Pt., a protected coast. Within sites the densities were not demonstrably different for horizontal surfaces. 5. Inhabitance of algal species varies with tidal height for Barleeia. At higher levels (4.0 ft. above 0.0 tide level) Rhodoglossum affine is prefered to Gigartina papillata while at lower levels (1.0 ft.) G. leptorhynchos is prefered to Rhodoglossum. 6. For Tricolia there is a change in plant occupancy with increasing size. Snails smaller than 1.5 mm occur predominantly in Gigartina leptorhynchos and G. canaliculata while the larger individuals have their greatest density on Rhodoglossum. 7. For Barleeia, there appears to be a downward movement when the snails reproductively mature as indicated by higher densities of both larger and smaller individuals at lower tidal levels.