Title

Ecophysiology and optical detection of harmful algal blooms

Date of Completion

January 2002

Keywords

Biology, Ecology|Biology, Oceanography|Environmental Sciences

Degree

Ph.D.

Abstract

Harmful algal blooms (HABs) adversely impact public and ecosystem health, the economy, seafood industry, and recreation. Examples of destruction include physical damage to other organisms, nutrient and oxygen depletion from the water, and the production of potent toxins, among other deleterious impacts. There are numerous harmful and/or toxic algal species, each with its own bloom dynamics and ecological controls. The purpose of this dissertation was to evaluate HAB physiology, ecology, and optical properties in order to understand the factors responsible for blooms and toxicity and to improve detection capabilities. ^ The physiology of Alexandrium, the toxic dinoflagellate responsible for paralytic shellfish poisoning (PSP), was examined in response to a range of environmental conditions. In particular, the effects of temperature, growth irradiance, and salinity on Alexandrium growth rates and toxin composition were determined. Alexandrium was also investigated as a possible source of PSP toxins found in abalone off the coast of South Africa. ^ Two HAB case studies provided information on bloom ecology. Alexandrium blooms in the Gulf of Maine were studied to assess the relationship between HAB physiology and ecology. Brown tides in Long Island embayments were also investigated to determine the role of ecology in bloom formation and the capability for optical detection of ecological processes. ^ The optical properties of several bloom-forming species were examined to determine what leads to the distinct ocean colors often associated with blooms, and existing bio-optical methods were evaluated under extreme algal bloom conditions. Additionally, the variability in Alexandrium optical properties as a function of environmental conditions was quantified to identify characteristics that may serve as diagnostics for physiological responses. Results demonstrated how optical techniques could be used to detect blooms and interpret physiological and ecological characteristics. ^ Thus, each chapter in this dissertation addresses the interconnections between HAB physiology, ecology, and optical properties. Specific significant results of this research include improved capabilities for predicting PSP events based on environmental conditions, novel toxin transference through the food web, determination of factors that lead to brown tide initiations, and improved understanding of optical methods that apply to extreme algal blooms. ^