Advisors: Dr. Miki Hondzo, Dr. Jacques Finlay
PhD Defense: December 16, 2011, 10 AM in the SAFL Auditorium
Abstract
Submerged aquatic vegetation (SAV), with its stems and leaves in the water column, strongly affects and is affected by the chemical and physical characteristics of the water. Epiphyte colonization of SAV surfaces alters its interaction with the water and modifies the effects of fluid flow on SAV photosynthesis and dissolved material uptake. The nature of these interactions was investigated through four separate studies. First, through a laboratory mesocosm experiment, epiphyte and SAV uptake of a dissolved contaminant (nickel) were quantified under various flow conditions. Second, a model was developed to determine rates of photosynthetic oxygen flux from the giant kelp, Macrocystis pyrifera in a moving fluid. The model was derived from the fundamental principles of conservation of mass and momentum over a flat plate using an integral method approach and is applicable in laminar, transitional and turbulent flows. Model predictions were experimentally validated with dissolved oxygen and velocity measurements above blades of giant kelp, Macrocystis pyrifera. Third, using microscale velocity imaging methods, photosynthesis was shown to alter fluid motion near the surface of a Cladophora spp. filament. Surface shear stresses for bare photosynthesizing algal filaments were 2.2 times greater than non-photosynthesizing filaments and 1.8 times greater than filaments with diatom dominated epiphyte assemblies. In the final study, epiphyte removal from submerged aquatic vegetation in a constructed wetland was shown to increase local dissolved oxygen concentrations throughout the water column as well as decrease soluble reactive phosphorus concentrations. Overall, through laboratory and field experiments, this thesis provides evidence that; a) SAV photosynthesis is coupled with fluid flow characteristics, b) SAV and epiphyte physiology are not equally affected by water motion, and c) epiphytes decrease SAV photosynthetic rates.
