1. Bamfield Marine Sciences Centre

2. Marine Ecology Class 2002

3. Feeding preference of Littorina snails (Gastropoda) for bleached and photosynthetic tissues of the seaweed Mazzaella parksii (Rhodophyta) by
Christine Heaven

4. Background
Littorina sp. shows a preference for Mazzaella parksii (Kim & DeWreede 1996)
High irradiance and desiccation levels lead to bleaching of tips; constitutes disruptive stress (Scrosati & DeWreede 1998)
Bleached tissue is less rigid; increased susceptibility to herbivory (Cronin & Hay 1996)

5. Mazzaella parksii

6. Importance? If red tissue is preferred: Whole blade is removed
Potential for Littorina sp. to control community structure
If bleached tissue is preferred:
Herbivore pressure is diverted away from healthy tissues
Blade can regenerate
Reproduction is enhanced

7. Research Question
Does Littorina sp. have a preference for certain tissue types?

8. Hypothesis
Littorina sp. will show a preference for either bleached, yellow-green, or red tissues

9. Experimental Design Goal: To measure the percent change
in biomass due to herbivory
Study Site: Prasiola Point,
Vancouver Island, B.C.
Experimental Unit: Mazzaella parksii tissue fragments

10. Prasiola Point

12. Results

14. What does this mean? Herbivore pressure is diverted to dead tissues
Littorina sp. does not have strong control over this community
Biomass remains in the system
Divergence of herbivore pressure through bleaching may be a result of algal evolution in response to grazing

15. Future Work
Determine chemical content of three tissues for nutritional value
Examine other locations for this preference
Field experiment to test whether dead tissues are removed by herbivores

17. Questions?