Relevant Degree Programs
Complete these steps before you reach out to a faculty member!
- Familiarize yourself with program requirements. You want to learn as much as possible from the information available to you before you reach out to a faculty member. Be sure to visit the graduate degree program listing and program-specific websites.
- Check whether the program requires you to seek commitment from a supervisor prior to submitting an application. For some programs this is an essential step while others match successful applicants with faculty members within the first year of study. This is either indicated in the program profile under "Requirements" or on the program website.
- Identify specific faculty members who are conducting research in your specific area of interest.
- Establish that your research interests align with the faculty member’s research interests.
- Read up on the faculty members in the program and the research being conducted in the department.
- Familiarize yourself with their work, read their recent publications and past theses/dissertations that they supervised. Be certain that their research is indeed what you are hoping to study.
- Compose an error-free and grammatically correct email addressed to your specifically targeted faculty member, and remember to use their correct titles.
- Do not send non-specific, mass emails to everyone in the department hoping for a match.
- Address the faculty members by name. Your contact should be genuine rather than generic.
- Include a brief outline of your academic background, why you are interested in working with the faculty member, and what experience you could bring to the department. The supervision enquiry form guides you with targeted questions. Ensure to craft compelling answers to these questions.
- Highlight your achievements and why you are a top student. Faculty members receive dozens of requests from prospective students and you may have less than 30 seconds to peek someone’s interest.
- Demonstrate that you are familiar with their research:
- Convey the specific ways you are a good fit for the program.
- Convey the specific ways the program/lab/faculty member is a good fit for the research you are interested in/already conducting.
- Be enthusiastic, but don’t overdo it.
G+PS regularly provides virtual sessions that focus on admission requirements and procedures and tips how to improve your application.
Graduate Student Supervision
Doctoral Student Supervision (Jan 2008 - Mar 2019)
Macroalgae living in wave-swept environments experience a high degree of mechanical stress. Flexible algae can mitigate this stress by bending with the waves, taking on smaller, more streamlined shapes that reduce drag. Coralline algae are limited in their flexibility due to having cell walls enriched in calcium carbonate, which cause thalli to be mostly rigid. While crustose species may avoid drag by growing prostrate along the substrate, most upright coralline species have uncalcified articulations (genicula) that allow them to retain flexibility despite their calcified constraint. Articulated corallines have evolved from crustose ancestors at least three separate times, leading to articulated species within the Corallinoideae, Lithophylloideae, and Metagoniolithoideae. The repeated evolution of genicula, and the rarity of upright coralline species without them, suggests that they play a key role in the ecological success of erect corallines. While previous studies have noted structural and developmental differences among genicula in the three evolutionary lineages, I address multiple levels of genicular organization to investigate the depth of convergent evolution of these structures. I found that genicular tissues are stronger and more extensible than other fleshy seaweed tissues, reflecting the fact that genicula must undergo a high degree of stress and strain to compensate for rigidity elsewhere in the algal thallus (Ch. 2). Differences exist between articulated clades; corallinoids are particularly strong, while lithophylloids are often highly extensible (Ch. 2). Articulated clades also differ in the way genicular morphology and tissue properties are adjusted to increase thallus flexibility; corallinoids possess a high number of genicula, metagoniolithoids possess long genicula, and lithophylloids possess particularly pliant genicular tissues (Ch. 3). Both the content and structure of polysaccharides in the genicular cell wall varies depending on subfamily, reflecting differences in genicular development and potentially causing differences in material properties (Ch. 4). Results from polarized microscopy suggest that the arrangement of polysaccharides within the cell wall also plays a role in how genicular tissue responds to mechanical stress (Ch. 5). In summary, while genicula may serve similar functions in corallinoids, lithophylloids, and metagoniolithoids, I show that there is more than one way to build an articulated coralline.
Climate change is progressing rapidly and is causing shifts in ecosystem function, species distributions, biodiversity, and abundances worldwide. In this thesis, I explore the physiological and biomechanical responses of red algae in multiple life history stages to climate change. In Chapter 1, I introduce the looming threat of climate change, and some of the forces driving ocean acidification. I introduce my study system and my study species: rocky intertidal ecosystems and articulated coralline algae. I also describe potential differences in responses to ocean acidification based on life history stage. Finally, I give an overview of my dissertation and objectives. In Chapter 2, I investigate the effect that ocean acidification may have on spore stages of red algae. Under reduced pH, I document a reduction in spore settlement of both Pterosiphonia bipinnata and Corallina vancouveriensis, and weakened spore attachment in C. vancouveriensis. Results demonstrate that ocean acidification can negatively impact macroalgal spore adhesion in both calcified and non-calcified algae, but in different phases of their spore adhesion process. In Chapter 3, I explore the effect of elevated pCO₂ and temperature on the growth, calcification, and material properties of two species of articulated coralline algae. I found that increased temperatures and reduced pH were found to negatively affect growth rates of these two species of coralline algae. On the other hand, increased temperature and reduced pH had little influence on the amount of calcium carbonate in the intergenicula, and also had minimal effects on the biomechanical properties. In Chapter 4, I explore the amount of natural variability of chemistry in tidepools and attempted to relate chemical differences to differences in Corallina vancouveriensis growth, calcification, and biomechanics. In general, I found that organisms within tidepools greatly alter the chemistry of the surrounding water, and these changes are larger in magnitude than what is predicted for global climate change. I also found that, despite extreme changes in chemistry during low tides, C. vancouveriensis was still able to grow all year long.
Master's Student Supervision (2010-2017)
Maintaining buoyancy with pneumatocysts is essential for subtidal seaweeds with long flexible thalli, such as Nereocystis luetkeana (Nereocystis), to achieve an upright stature and compete for light. However, as Nereocystis grows, pneumatocysts are exposed to significant changes in hydrostatic pressure. Exposure to changing hydrostatic pressure could cause complications since the pneumatocyst is filled with gases that may expand or contract, potentially causing pneumatocysts to break, flood, and no longer be buoyant. This study explored how Nereocystis pneumatocysts resist biomechanical stress and keep the developing sporophyte upright in the water. Throughout development, pneumatocysts had an internal pressure consistently less than atmospheric pressure (3 – 100 kPa), indicating pneumatocysts always experience compressional loads. The structural integrity and design of the pneumatocyst to resist buckling was assessed by measuring compressional modulus (material stiffness), calculating material stress, analyzing critical geometry, and estimating critical buckling pressure. Small pneumatocysts found at depth (inner radius = 0.8 - 0.9 cm; wall thickness = 0.2 cm) were demonstrated to have reached a critical size in development and are at greatest risk of buckling. Pneumatocysts do not adjust material properties or geometry to reduce wall stress, but they are naturally resistant to hydrostatic loads. Critically small pneumatocysts are estimated to buckle at 35 m depth, which was observed to be sporophytes’ lower limit in the field. Data suggest that hydrostatic pressure, not just light limitation, might explain the maximum depth to which Nereocystis is capable of growing. Pneumatocyst gas composition did not change throughout development, and contrary to previous studies, internal gas concentrations were different from the atmosphere with O₂, N₂, CO, and CO₂ concentrations of 59%, 40%, 1.6%, and 0.6% respectively. Furthermore, pneumatocyst surface area to volume ratio did not correlate with the exchange of gases produced from photosynthesis and respiration. As sporophytes grow, total buoyant force is steadily outpaced by the weight of growing thalli, and the risk of the pneumatocyst sinking increases. Adult sporophytes are estimated to sink when pneumatocysts volume reaches 1.3 L, close to the maximum observed size in the field.
Organisms in the intertidal zone are regularly exposed to wave action, emersion, and competition. Competition for space may have been a factor leading to the evolution of epiphytes which have circumvented this problem by growing on other algae. Epiphytism is generally considered deleterious to hosts but, is this always true? This study explored costs and benefits of interactions between the epiphyte, Soranthera ulvoidea, and its host, Odonthalia floccosa, involving biomechanics, light acquisition, desiccation, and herbivory. Drag on epiphytized and unepiphytized hosts was measured in a recirculating water flume. Epiphytes increased drag on hosts by approximately 50% at each test velocity. Increased drag caused epiphytized hosts to be more likely to break from the substratum than hosts without epiphytes. Epiphytes experienced reduced drag when attached to hosts but sometimes broke before hosts. In fact, epiphytized hosts and epiphytes were equally likely to dislodge; this suggests that drag added by epiphytes may not be entirely harmful to hosts if epiphytes dislodge half the time, reducing overall drag on epiphytized hosts. The effects of epiphytism on light acquisition, desiccation, and herbivory were also investigated. Photosynthesis versus irradiance curves were constructed for hosts and epiphytes; saturation irradiances for both were approximately 50μmol m⁻²s⁻¹, and were not significantly different from irradiances under submerged algal canopies in the field. Thus, it was inferred that these epiphytes do not likely affect host light acquisition. Also, these epiphytes may not have arisen in response to light limitation as they reached photosynthetic saturation when exposed to light levels under other algae. When hosts with and without epiphytes were exposed to air, epiphytes doubled the time required for hosts to lose 50% of the water originally associated with their thalli. By delaying desiccation, epiphytes likely reduce physiological damage of emergent hosts. Lastly, invertebrate herbivores common to this study’s field site preferred grazing epiphytes over hosts. This feeding preference could benefit hosts by diverting herbivores away from host tissue and toward epiphytes. In sum, this study demonstrates that hosts and epiphytes often benefit by closely associating; these complex interactions could help explain the evolution and persistence of intertidal algal epiphytism.
Intertidal macroalgae endure stresses associated with submerged and emerged conditions on a daily basis. Differences in physiology at high tide, low tide, and during recovery underlie spatial separation of species along the shore. Tidepools provide refugia from physical stresses associated with the low tide, and species with low stress tolerance may be restricted to these habitats. Species that survive emergence employ physiological and morphological strategies to survive exposure to pseudo-terrestrial conditions. I explored how tidepool and non-tidepool macroalgae respond to and recover from intertidal stressors, such as light, temperature, and desiccation. I investigated whether differences in physiology could explain differences in habitat distributions. To answer these questions, I explored the physiological responses of the coralline algae, Calliarthron tuberculosum (Postels and Ruprecht) E.Y. Dawson and Corallina vancouveriensis Yendo, to simulated tidal conditions. Calliarthron is restricted to tidepools, while Corallina can survive emersion during low tide. First, I documented physiological differences between the two species at high tide. Corallina performed similar to a high light adapted plant, while Calliarthron’s performance resembled that of a low light adapted plant. Surprisingly, their pigment composition did not differ, suggesting that both species are able to harvest light similarly but that other metabolic processes are at play. Second, I compared morphological and physiological strategies employed by Calliarthron and Corallina to resist stress during low tide. I found differences in the physiological responses of the two species to increased light and temperature, two chief stressors present in the tidepool microhabitat. Unlike Calliarthron, Corallina exhibited high tolerance to increasing water temperatures and was more effective at resisting desiccation via morphology. However, neither species photosynthesized in the air, regardless of hydration level. Finally, I quantified recovery upon the return of the tide. Both species recovered from warm tidepool temperatures. However, only Corallina recovered from the combination of temperature and desiccation stress associated with emergence.This study describes the variation in physiological performance of two intertidal macroalgal species during the tidal cycle, and documents several morphological and physiological strategies employed by species to survive stresses associated with low tide. Results help to explain the habitat differences between the two species.