Thesis (Ph. D.)--Simon Fraser University, 2000. / Includes bibliographical references (p. 139-155).

Thesis (doctoral)--Universität Bremen, 2005. / Includes bibliographical references.

I examined the biomechanical factors that influence the sizes of intertidal macroalgae by studying a population of Fucus gardneri at Fogarty Creek Point, OR. I constructed a mathematical model to predict optimal sizes and probabilities of survival for Fucus under conditions of high and low wave exposure. Predicted optimal sizes of Fucus closely matched the mean observed sizes of plants collected from wave-exposed and protected locations. To test this hypothesis in the field, I reciprocally transplanted Fucus between wave-exposed and wave-protected sites and found that the degree of wave exposure did not affect survival, but did influence size. Large Fucus were tattered by waves at exposed sites, and small Fucus grew at protected sites. These results support the hypothesis that wave forces can set mechanical limits to size in Fucus. I experimentally examined the relative influences of wave-induced disturbance, competition and predation on the sea palm, Postelsia palmaeformis and its understory community at a wave-exposed site at Depoe Bay, OR. Postelsia recruitment was affected by seasonal variations in disturbance and was greatest in areas disturbed in winter. Postelsia were most abundant at mid-zone, wave-exposed sites, and their restriction to wave-exposed sites seems to be due both to; 1) the occurrence of predictable winter disturbances at these sites which remove mussels, thereby stimulating sea palm growth from the underlying rock, and 2) high water motion which enhances sea palm growth by increasing nutrient exchange and photosynthesis and preventing desiccation at low tide. Competition, disturbance and grazing were all important factors in structuring the Postelsia understory community. Postelsia were dominant competitors and their holdfasts overgrew low-lying plants which were torn loose with Postelsia when this kelp was dislodged by winter storm surf. In the absence of this predictable, seasonal disturbance, competitive understory species, such as Corallina dominated primary space. Intermediate levels of disturbance allowed for the highest understory species diversity. Limpets played a keystone role by grazing Postelsia, the competitive dominant during most of the year, and maintained high levels of species diversity in the algal understory. / Graduation date: 1995

Le travail réalisé au cours de cette thèse s'intègre dans la problématique générale de l'étude des processus de spéciation, en prenant comme espèces modèles de grandes algues brunes marines (Ordre des Laminariales, appelées " kelps "). Ces algues forment de véritables forêts dans les eaux tempérées froides et ont une importance économique, pour l'industrie des alginates et pour la récolte d'invertébrés marins vivant dans ces forêts. Malgré leur importance écologique et économique, et leur grande diversité en nombre d'espèces dans certaines régions du monde, les mécanismes favorisant la spéciation et contribuant à l'isolement reproducteur ont été très peu étudiés chez ces espèces. Mon travail de thèse a permis de mettre en évidence l'existence de deux espèces cryptiques au sein du complexe " Lessonia nigrescens " le long des côtes chiliennes. Je me suis tout d'abord attachée à comprendre l'histoire des deux taxa, et à discuter les différentes hypothèses à l'origine de cette spéciation. Ensuite, je me suis intéressée aux mécanismes qui permettent actuellement le maintien de l'intégrité des espèces cryptiques de L. nigrescens, en particulier dans la région de contact entre leurs aires de distribution.

Konstanz, Univ., Diplomarb., 2004.

"November 2001" / Bibliography: leaves 132-156. / xii, 166 leaves : ill. (some col.), plates (col.) ; 30 cm. / Title page, contents and abstract only. The complete thesis in print form is available from the University Library. / Focusses on the ecophysiology of Ecklonia radiata and quantifies its carbon contribution to further elucidate E. radiata's role in the nearshore marine environment. The photosynthesis-irradiance response of E. radiata was investigated in situ throughout the year and across the dept profile. A clear seasonal change in photokinetic parameters was detected and provided strong evidence of a seasonal acclimation response. Changes in photokinetic parameters across the depth profile were less pronounced and a significant decline in productivity occurred at deeper depths. The acclimation state of E radiata did alter across the depth profile. / Thesis (Ph.D.)--University of Adelaide, Dept. of Environmental Biology, 2002