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Bamfield Marine Sciences Centre

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  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

  11. Results

  12. What does this mean? • Herbivore pressure is diverted to dead tissues • Littorina sp. may 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

  13. 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

  14. Questions?