| The purpose of this research was to quantify the occurrence of the chlorophyte, Codium fragile (Suringar) Hariot in Barkley Sound, British Columbia habitats and explore several factors that may be correlated to its patchy distribution. Codium fragile is a unique species for study as it is a coenocytic seaweed found in physically-stressful habitats; specifically, rocky intertidal areas. Many previous studies have focused on the invasive nature of a closely-related subspecies (Codium fragile ssp. tomentosoides), however, few studies have examined the biology and ecology of native C. fragile on NE Pacific shores.; I conducted feeding preference, absorption efficiency, and macroalgal diet vs. fitness experiments using generalist herbivores (e.g. purple urchins and black chitons) and three common intertidal seaweeds (e.g. Codium fragile, Hedophyllum sessile, Mazzaella splendens). My results show that compared to the two other seaweeds, C. fragile is not preferred by purple urchins or black chitons, it has the lowest (short-term) nutritional value, and did not significantly increase somatic or reproductive growth for either herbivore species.; I estimated maximum wave forces for each of my four study sites in order to classify them as wave-protected or wave exposed. I measured the force to remove or break Codium fragile plants from their attachment on rocky substratum, comparing size classes as well as origin of representative C. fragile plants. Measured drag coefficients show that C. fragile conforms to increased water velocities (similar to other algal species). Large C. fragile plants are more susceptible to increased velocities than smaller plants; plants growing at Scott's Bay are more likely to break or detach compared to plants from other locations.; This thesis advances our minimal knowledge of native Codium fragile plants in NE Pacific habitats, compared to the wealth of information on the invasive subspecies, C. fragile ssp. tomentosoides . My research is original as it measures the effects of both biotic and abiotic factors on a coenocytic macroalgal species found in rocky, intertidal habitats. Of the three factors I chose to study, herbivory is widespread throughout published ecological literature whereas effects of sand burial are few. Furthermore, my wave action results contribute to an emerging field of study in marine science---increasing our understanding of how seaweeds persist in wave-swept environments. (Abstract shortened by UMI.)... |
