Bamfield Marine Sciences Centre

Marine Ecology Class 2002

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

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)

Mazzaella parksii

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

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

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

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

Prasiola Point

Results

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

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

Questions?