Master of Science (M.Sc.)
Virginia Institute of Marine Science
Juliette L Smith
Michael A Unger
William G Reay
Allen R Place
Harmful algae can illicit adverse effects on aquatic and human health through various mechanisms, including through the production of bioactive compounds called phycotoxins. In the Chesapeake Bay, the largest estuary in the United States, little information was known about the distribution of phycotoxins, even though this region is known to harbor 37+ different species of harmful algae. Due to the presence of multiple species that can produce distinct groups of phycotoxins, a multi-toxin approach was taken to study this region. Two methods for the quantification of 13 phycotoxins (microcystin-RR, -LR, YR, azaspiracid-1, -2, karlotoxin 3, goniodomin A, yessotoxin, brevetoxin-2, pectenotoxin-2, okadaic acid, dinophysistoxin-1, and -2) in a single sample were developed using novel technology: ultra-performance liquid chromatography coupled to tandem mass spectrometry equipped with a trapping dimension and at-column dilution. This instrumentation allows for high-volume (up to 1 mL) injections of extracts in 100% organic solvents, reducing time and labor normally required for sample preparation steps and resulting in low limits of detection compared to current literature values. To evaluate the distribution of these phycotoxins and their causative species in the environment, a field study was carried out at 12 sites in the lower Chesapeake Bay between May 2017 and June 2018. Solid Phase Adsorption Toxin Tracking (SPATT), a passive sampling technique for dissolved phycotoxins, was used throughout the field study. The resulting dataset allowed for a spatiotemporal comparison of these compounds across the region. Surface water samples were also enumerated by light microscopy to compare toxin amounts to the presence of harmful algal cells, and environmental parameters (e.g. temperature, salinity) were evaluated over the course of the study to determine if any correlations existed with toxin data. Before samples could be analyzed, a method suitable for the extraction of multiple toxins from SPATT resin (Diaion® HP-20) was developed. The developed multi-toxin methods for extraction and quantification were then applied to SPATTs collected during the field study, and additional analyses for domoic acid were performed using enzyme-linked immunosorbent assays. Out of 15 toxins analyzed for, 8 were detected in this region: microcystin-LR, azaspiracid-1, azaspiracid-2, goniodomin A, pectenotoxin-2, okadaic acid, dinophysistoxin-1, and domoic acid. This study marks the first report of azaspiracids in Chesapeake Bay, and is among the first to report domoic acid in this region. While multiple toxins were present in samples from all 12 sites throughout the study period, harmful algae were sparse in corresponding water samples. This finding stresses the usefulness of passive sampling, a method that provides an integrated measurement of trace amounts of toxin present in the water column. The results from this study show that multiple phycotoxins, spanning both salt- and fresh-water origin, are present throughout the lower Chesapeake Bay. This region, however, does not see recurring seafood harvest closures or human health illnesses due to phycotoxin contamination, suggesting that amounts of these compounds are currently low enough to avoid major human health implications. The potential for low-level chronic exposure remains possible, and these results highlight the importance of considering the effects of chronic exposure to environmental contaminants.
© The Author
Onofrio, Michelle D., "Spatial And Temporal Distribution Of Phycotoxins In Lower Chesapeake Bay: Method Development And Application" (2020). Dissertations, Theses, and Masters Projects. Paper 1593091873.
Available for download on Saturday, May 08, 2021