Date of Award

Summer 8-9-2022

Level of Access Assigned by Author

Open-Access Dissertation

Degree Name

Doctor of Philosophy (PhD)

Department

Oceanography

Advisor

Andrew C. Thomas

Second Committee Member

Emmanuel Boss

Third Committee Member

David W. Townsend

Additional Committee Members

Ivona Cetinć

William M. Balch

Abstract

Harmful Algal Blooms (HABs) of the toxic dinoflagellate Alexandrium catenella are an annually recurring problem in the Gulf of Maine (GoM), resulting in risks to human health and substantial economic losses due to shellfish harvesting closures. The monitoring approaches in the region are restricted to real-time identification of the HABs events, when they are clearly underway and already causing deleterious effects to the environment. To fully function as an early warning system rather than an immediate response, monitoring strategies need to be focused on environmental conditions preceding A. catenella HABs. However, the current understanding of the preferred habitat for A. catenella in the GoM is still scarce due to the complex interactions between this organism and the environment. My dissertation research contributes to the solution of these problems by determining the preferred thermal habitat for A. catenella, contrasting environmental conditions for two extremes in A. catenella concentration, and exploring the benefits of using high resolution spectral data to characterize the GoM surface waters. This dissertation is focused on the application of current and future remote sensing technology to the measurement and management of GoM HABs. Chapter 1 briefly introduces the problematic of HABs, monitoring efforts and the study species. Chapter 2 characterizes the interannual variability in the thermal habitat and bloom phenology of A. catenella in the Bay of Fundy, identifying the environmental conditions associated with this variability and its responses to climate change. Chapter 3 contrasts the optical and thermal conditions associated with two extremes in A. catenella concentration over multiple years and areas in the GoM and establishes a set of typical water types for each concentration category. Chapter 4 characterizes the spatial and temporal variability of hyperspectral reflectance of surface waters in the GoM and determines the advantage of hyperspectral resolution over multispectral to identify important spatial patterns and regions. Chapter 5 will conclude with a discussion on the implications of these results to monitoring efforts in the GoM, implications of climate change, and discusses future directives to further explore habitat suitability approaches in monitoring efforts.

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